https://www.onelab.mit.edu/home daily 1.0 2025-02-20 https://images.squarespace-cdn.com/content/v1/60073f823d27c928fce58f8f/1611088779146-KM7CA2ASF1L91A7AX5KL/image.jpeg Home - Next Generation Optoelectronic Devices We study the physical and chemical properties of nanostructured thin films and devices. Based on our fundamental findings, we develop the next generation of high-performance optoelectronic and photonic devices, including solar cells, LEDs, lasers, photodetectors, transistors, and chemical sensors. https://images.squarespace-cdn.com/content/v1/60073f823d27c928fce58f8f/1611089151762-QUE8QACIL1KSKFA3VLEP/image.jpeg Home - MIT.Nano A nanometer is a mere one billionth of a meter. If you were to travel 50,000 nanometers, you'd only be halfway across the width of a human hair. But researchers have discovered that matter at this scale behaves in revolutionary ways. Twenty-five years of intensive research now gives us the power to reshape our world from the nanoscale up. https://images.squarespace-cdn.com/content/v1/60073f823d27c928fce58f8f/1611089614107-KHF1N0A7HWVXYIU5BKK7/image.png Home - Incubating Startups Bulović co-founded three start-up companies, which jointly employ over 400 people in solar technologies, printed electronics, and quantum dot optoelectronic components. https://www.onelab.mit.edu/excitonics daily 0.75 2022-05-29 https://www.onelab.mit.edu/light-sources daily 0.75 2021-01-19 https://www.onelab.mit.edu/nanomechanics daily 0.75 2021-01-19 https://www.onelab.mit.edu/solar-technologies daily 0.75 2021-01-19 https://www.onelab.mit.edu/team daily 0.75 2026-04-01 https://images.squarespace-cdn.com/content/v1/60073f823d27c928fce58f8f/1611093497073-DTT2H9WA90GWH0GA6Y97/Screen+Shot+2021-01-19+at+4.57.51+PM.png Team 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https://images.squarespace-cdn.com/content/v1/60073f823d27c928fce58f8f/f01d0e3f-0a9e-4142-b63b-7f7ee460d64e/DSC02434.jpg https://images.squarespace-cdn.com/content/v1/60073f823d27c928fce58f8f/d68bd502-0ad7-457a-936d-931064d2f19d/IMG_1410.JPG https://images.squarespace-cdn.com/content/v1/60073f823d27c928fce58f8f/fe44be2c-d0e4-4520-8398-5ac1ce16e339/IMG_1411.JPG https://images.squarespace-cdn.com/content/v1/60073f823d27c928fce58f8f/02978a39-2041-40bd-b999-2cad15a1743f/PXL_20240123_180328657.jpg https://images.squarespace-cdn.com/content/v1/60073f823d27c928fce58f8f/73b262ba-b487-4cfa-ba51-70b1cffa9a21/53498764978_56eb03279d_o.jpg https://images.squarespace-cdn.com/content/v1/60073f823d27c928fce58f8f/7949fda5-8f32-4a34-ba58-db1c2b86ae93/IMG_1413.JPG https://www.onelab.mit.edu/contact daily 0.75 2022-05-29 https://www.onelab.mit.edu/publications daily 0.75 2021-03-01 https://images.squarespace-cdn.com/content/v1/60073f823d27c928fce58f8f/1614622757138-6Y93BMNEC7G9I62BSAFL/IMG_2019.jpeg Publications - Learn more. Check out recent publications from the ONE Lab and collaborators: https://www.onelab.mit.edu/startups daily 0.75 2021-03-01 https://images.squarespace-cdn.com/content/v1/60073f823d27c928fce58f8f/1611113602285-LLQHU2X7OQFNWWI0BHN4/image.jpeg Startups https://images.squarespace-cdn.com/content/v1/60073f823d27c928fce58f8f/1611113480575-Z4ISBL9R0O9SV8EHQ7IC/image.jpeg Startups https://images.squarespace-cdn.com/content/v1/60073f823d27c928fce58f8f/1611113511879-58TSSTFBB1PHEOVHIWFM/image.png Startups https://images.squarespace-cdn.com/content/v1/60073f823d27c928fce58f8f/1611114142247-6ES00MPFPYZK9GIDLZ61/IMG_1315.jpeg Startups - Contact us. onelabcontact@mit.edu 77 Massachusetts Ave Cambridge, MA 02139 https://www.onelab.mit.edu/alumni daily 0.75 2025-09-29 https://www.onelab.mit.edu/vladimir-bulovi daily 0.75 2025-02-20 https://images.squarespace-cdn.com/content/v1/60073f823d27c928fce58f8f/1611093670332-M34RS9MTLYM55FCFKZDS/Screen+Shot+2021-01-19+at+4.57.51+PM.png Vladimir Bulović - Vladimir Bulović Tobias Keene, D.D.S. Hailing from Richmond, Virginia, Dr. Tobias Keene brings a bit of unabashed Southern hospitality to all his patients. He moved to Washington, D.C. over thirty years ago as a freshman at Ivy College. Right after graduation, he attended World University’s School of Dentistry. Before opening Keene Dental in 1994, he worked for free clinics and some of the finest practices in the District. He is part of the 123 Dental Association and stays up-to-date on the latest dental discoveries. When not striving to keep his patients happy and healthy, he’s enjoys hiking with his family in Rock Creek Park. https://www.onelab.mit.edu/nicky-evans daily 0.75 2025-02-20 https://images.squarespace-cdn.com/content/v1/60073f823d27c928fce58f8f/b8d8d474-62b7-4b34-8622-ea8e29ce1552/2f7a9c18-477c-40a8-98a6-03e042871cc9.jpg Nicky Evans - Nicky Evans Postdoctoral Associate at the Research Laboratory of Electronics (RLE) Nicky Evans (British Bestie) joined the ONE Lab in the fall of 2024. He received his MPhys (Physics) from the University of Surrey, UK, in 2020 and his PhD in Physics from the University of Oxford, UK, in 2024. With a background in both organic and perovskite photovoltaics, Nicky’s PhD involved investigations into intrinsic and doped transport layers in solar cells, utilising electronic and spectroscopic characterisation techniques. Having previously been a research student with OPVIUS GmbH (now ASCA solar films) in 2019, Nicky has experience with optimising the laser patterning of commercial OPV modules to improve throughput. He is co-advised by Professor Tonio Buonassisi. Subgroup: Solar Technologies Current Research: He is currently working on meniscus coating techniques for scale-up of perovskite photovoltaics. Email: nickye17@mit.edu Office: 13-3078 https://www.onelab.mit.edu/tamar-kadosh daily 0.75 2025-09-29 https://images.squarespace-cdn.com/content/v1/60073f823d27c928fce58f8f/cebf4753-8a74-4027-b4ec-43e9f677122f/Tamar.png Tamar Kadosh - Tamar Kadosh PhD Student in DMSE Tamar Kadosh joined ONE Lab in November 2021 as PhD in Materials Science and Engineering. She previously received her B.Sc. in Chemical Engineering and M.Sc. in Materials Science and Engineering from the Technion institute of Technology in Haifa, Israel. Her previous research experience focused characterizing ceramic suspensions. She is co-advised with Professor Harry L. Tuller in the Department of Materials Science and Engineering. Subgroup: Solar Technologies Current Research: Implementing and optimizing Vapor Transport Deposition processes of perovskites to promote solar cells scalability. Email: tamarka@mit.edu Office: 13-4010 https://www.onelab.mit.edu/ruiqi-zhang daily 0.75 2025-09-29 https://images.squarespace-cdn.com/content/v1/60073f823d27c928fce58f8f/7e470824-c146-442a-ad9d-0ee7890c2dda/Ruiqi+RLE+2022+Picture.jpg Ruiqi Zhang - Ruiqi (Ricky) Zhang PhD Student in EECS Ruiqi Zhang joined ONE lab in the spring of 2022 as a PhD candidate in Electrical Engineering and Computer Science. He received his B.S. Degree in Nanoengineering with a minor in Mathematics at UC San Diego in 2021. His previous works focus on developing flexible single-crystalline metal halide perovskite devices including solar cell, LED, FET and laser diode. He also studied the material and device physics of perovskite thin films and III-V group semiconductors. He is currently working on Quantum Dots LED fabrication, characterization and utilizing Machine Learning Approaches to investigate Next generation Perovskite Solar Cells. Subgroup: LED Technologies, Solar Technologies Current Research: QD-LEDs developments and ML approach in predicting metal halide perovskite solar cell properties. Email: rqzhang@mit.edu Office: 13-3078 https://www.onelab.mit.edu/tori-dang daily 0.75 2025-09-29 https://images.squarespace-cdn.com/content/v1/60073f823d27c928fce58f8f/7bbea519-63a1-4b05-8835-9a5def17412e/Tori+Dang.jpg Tori Dang - Tori Dang PhD Student in Electrical Engineering Tori Dang joined the ONE lab in 2022 as a PhD student in Electrical Engineering. She received her B.A. in Physics and Italian from Bryn Mawr College in 2020, and her M.S.E in Electrical Engineering from the University of Pennsylvania in 2021. Her prior work focused on nanofabrication and developing diamond metasurfaces for nanophotonic applications. Currently, she is working on the design and fabrication of acoustically active surfaces. Subgroup: Nanomechanics Current Research: Development of acoustic surfaces Email: tongdang@mit.edu Office: 13-3153 https://www.onelab.mit.edu/shreyas-shrinivasan daily 0.75 2025-09-29 https://images.squarespace-cdn.com/content/v1/60073f823d27c928fce58f8f/a3946023-0751-4452-bb43-d9f466088ad3/20220514-8.jpg Shreyas Shrinivasan - Shreyas Srinivasan PhD Student in Chemistry Shreyas Srinivasan joined the ONE Lab in the fall of 2022 as a Ph.D. student in Chemistry. He received his B.S. and M.S. in Chemistry from Carnegie Mellon University in 2022. His prior work explored the synthesis and application of atomically precise metal nanoclusters as electrocatalysts. Presently, he is researching the development of a vacuum-transport deposition system for the production of metal-halide perovskite solar cells. He is also researching the fabrication of nanoscale plasmonic optical cavities for use in colloidal quantum dot lasers. He is co-advised with Professor Moungi G. Bawendi in the Department of Chemistry. Subgroup: LED Technologies, Solar Technologies Current Research: Vacuum transport deposition of perovskite solar cells and optical cavities for colloidal quantum dot lasers Email: shreyas2@mit.edu Office: 2-216a https://www.onelab.mit.edu/karen-yang daily 0.75 2025-09-29 https://images.squarespace-cdn.com/content/v1/60073f823d27c928fce58f8f/8c72e925-25eb-4d39-ae4e-ff21a10256c6/profile_pic_pumpkins.jpg Karen Yang - Karen Yang Tobias Keene, D.D.S. Hailing from Richmond, Virginia, Dr. Tobias Keene brings a bit of unabashed Southern hospitality to all his patients. He moved to Washington, D.C. over thirty years ago as a freshman at Ivy College. Right after graduation, he attended World University’s School of Dentistry. Before opening Keene Dental in 1994, he worked for free clinics and some of the finest practices in the District. He is part of the 123 Dental Association and stays up-to-date on the latest dental discoveries. When not striving to keep his patients happy and healthy, he’s enjoys hiking with his family in Rock Creek Park. https://www.onelab.mit.edu/mike-dillender daily 0.75 2025-09-29 https://images.squarespace-cdn.com/content/v1/60073f823d27c928fce58f8f/46861f06-764c-4b85-a614-3c05effcd7c1/Picture1.png Mike Dillender - Mike Dillender PhD Student in EECS Mike Dillender joined the ONE lab in the summer of 2024 as a PhD student in Electrical Engineering and Computer Science. He received his B.S. in electrical engineering with minors in physics and computer science at the University of Michigan in 2024. His prior work focused on Nanophotonics manipulation of exciton transport in TMDCs and designing free-space spectroscopy systems. Subgroup: LED Technologies Current Research: Email: dil@mit.edu Office: 13-3078 https://www.onelab.mit.edu/stella-lessler daily 0.75 2025-09-29 https://images.squarespace-cdn.com/content/v1/60073f823d27c928fce58f8f/08ed21de-0eac-4469-9ab0-3f2222215055/tempImaged4eKwu.jpg Stella Lessler - Stella Lessler PhD Student in EECS Stella Lessler joined ONE Lab in the fall of 2024 as a PhD student in Electrical Engineering and Computer Science. She received her B.S. in Electrical Engineering at Columbia University in 2024. Her prior work focused on utilizing block copolymer self assembly patterning for vertical transistor fabrication. Subgroup: Solar Technologies Current Research: Email: stells13@mit.edu Office: 13-3078 https://www.onelab.mit.edu/jackie-zheng daily 0.75 2025-09-29 https://images.squarespace-cdn.com/content/v1/60073f823d27c928fce58f8f/7383d33b-4f95-4e8a-ad2d-93a7916000e8/IMG_7720.jpg Jackie Zheng - Zhangqi (Jackie) Zheng PhD student in EECS Jackie Zheng joined ONE lab in the fall of 2024 as a PhD student in Electrical Engineering and Computer Science. She received her B.S. in Engineering Physics with a minor in Computer Science at the Cornell University in 2024. Her previous work focused on micro-robotics, and more specifically on fabrication and characterization of electrochemical actuators with nanoscale thickness. Currently, she is working on developing MEMS devices at both the nano-scale for electronics applications, as well as a larger scale for acoustics. Subgroup: Nanomechanics Current Research: Acoustically active thin-film devices and nano-scale electromechanical switches. Email: zqzheng@mit.edu Office: 13-3157 https://www.onelab.mit.edu/baron-and-max daily 0.75 2025-03-03 https://images.squarespace-cdn.com/content/v1/60073f823d27c928fce58f8f/2927f182-0d6e-4e48-9274-f498808dd882/1441871882899273312.jpg Baron and Max - Max PostDog MIT Boundless Energy Fellow Max earned his dogtorate from UC Barkley and became a PostDog at MIT at the age of 1 (the youngest in OneLab!), focusing on finding, inspecting and studying sticks. His work lead to the aggregation and analysis of at least 10 sticks in a variety of shapes and sizes, and has resulted in several puplications. In OneLab, his work is supportive in nature. He is in charge of playing with tennis balls in the main office and going on walks around the Charles River. His door is always open to anyone who wants to play, but he insists they must also bring snackies. Subgroup: Pawptics and spectroscopuppy Current Research: Stick inspection for next-gen fetch https://images.squarespace-cdn.com/content/v1/60073f823d27c928fce58f8f/14cc4c3a-e87a-4329-82e2-c6326fba718b/3323279990650631082.jpg Baron and Max - Baron PostCat MIT Boundless Energy Fellow Baron earned his catademic degree from Purrinceton and became a PostCat at MIT at the age of 7, specializing in the rigorous analysis of small, elusive objects, particularly crinkly balls and stray paper clips. His groundbreaking work has contributed to the categorization of over 15 objects knocked off tables, with results featured in several peer-revurred journals. At any given moment, Baron may or may not be present— widely believed to be Schrödinger’s cat, existing in a superposition of napping and causing chaos until directly observed.In OneLab, his role is primarily supervisory—overseeing experiments from the highest available perch, providing critical input during Zoom calls, and ensuring optimal keyboard disruption protocols. His office hours are always open for cuddles, but all visitors must pay the entry fee of head scratches or treats. Subgroup: Quantum Pawdynamics and Feline-terferometry Current Research: Box occupancy optimization and laser pointer trajectory prediction https://www.onelab.mit.edu/jocelyne-zhang daily 0.75 2025-02-20 https://images.squarespace-cdn.com/content/v1/60073f823d27c928fce58f8f/cfad644b-48bf-45b0-96d4-482c0eb717c5/headshot.JPG Jocelyne Zhang - Jocelyn Zhang Undergraduate Student (UROP) in EECS Jocelyn Zhang joined ONE lab in the fall of 2024 as an Undergraduate Student in Electrical Engineering and Computer Science. Her previous work focused on the long-lived trap state of silicon quantum dots in a porous silicon matrix and characterization of ion bombardment on polymer thin films. https://www.onelab.mit.edu/thienan daily 0.75 2025-02-20 https://images.squarespace-cdn.com/content/v1/60073f823d27c928fce58f8f/537c267a-c24c-41b8-90f6-139638b0bf44/photo.jpeg Thienan - Thienan Nguyen MENG Student in EECS Thienan Nguyen joined ONE lab as a UROP in Spring of 2022 and is continuing as an MENG since Fall of 2024. He received his B.S. in Electrical Engineering and Computer Science from MIT in 2024. His previous work includes x-ray characterization of vapor deposited perovskite films for solar cells. Presently, he is researching the electrical characteristics of colloidal quantum dot LEDs at low temperatures. Subgroup: LED Technologies Current Research: Temperature JVL characterization of colloidal quantum dot LEDs. Email: thienann@mit.edu Office: 13-3154 https://www.onelab.mit.edu/rahul daily 0.75 2025-03-13 https://images.squarespace-cdn.com/content/v1/60073f823d27c928fce58f8f/8873f531-e9be-4120-9106-2e8f3dba0f8d/photo.jpg Rahul - Rahul Patidar Postdoctoral Associate at the Research Laboratory of Electronics (RLE) Rahul Patidar joined the ONE Lab in early 2025. He holds a BS-MS (Dual Degree) from the Indian Institute of Science Education and Research (IISER) Pune, India (2018), and earned his PhD in Materials Engineering from Swansea University, UK (2023), supported by Marie Skłodowska-Curie Actions Horizon 2020 scholarship. During his doctoral studies, Rahul focused on advancing scalable manufacturing techniques for perovskite solar cells, specializing in the optimization of slot-die coating and drying processes within roll-to-roll (R2R) production systems. He also worked on developing low-toxicity solvent formulations tailored for R2R compatibility. Subgroup: Solar Technology Current Research: Email: patidar@mit.edu Office: 13-3154 https://www.onelab.mit.edu/rahul-1 daily 0.75 2025-09-29 https://images.squarespace-cdn.com/content/v1/60073f823d27c928fce58f8f/9fdd0fb5-fb26-4c05-84ba-dfb1774dcb19/100e7079-e9dc-43c7-a3c1-9518893a8c00.JPG Sage - Sage Martin PhD student in EECS Sage Martin joined ONE lab in September 2025 as a PhD student in Electrical Engineering. He received a Bachelor of Materials Science and Engineering from the University of Minnesota in May of 2025. At UMN, he studied spontaneous orientation polarization in materials used in OLED technologies. Sage has also worked as an intern at Intel in Oregon and Polar Semiconductor in Minnesota. Subgroup: LED Technology Current Research: Email: scmart@mit.edu Office: 13-3078 https://www.onelab.mit.edu/rahul-2 daily 0.75 2026-04-01 https://images.squarespace-cdn.com/content/v1/60073f823d27c928fce58f8f/cf05da37-1127-44dc-8cf0-6a98b04b38de/DSC03672.jpg Sam - Samantha T Farrell Lab Administrator LinkedIn: https://www.linkedin.com/in/samantha-farrell-a9719024/ https://www.onelab.mit.edu/research daily 0.75 2021-01-20 https://www.onelab.mit.edu/research/solar-technologies monthly 0.5 2021-01-19 https://images.squarespace-cdn.com/content/v1/60073f823d27c928fce58f8f/8d4bec8f-0271-4598-a13b-870d917017b0/Screen+Shot+2022-03-29+at+10.35.53+PM.png Research - Solar Technologies - Processing Induced Distinct Charge Carrier Dynamics of Bulky Organic Halide Treated Perovskites. State-of-the-art metal halide perovskite-based photovoltaics often employ organic ammonium salts, AX, as a surface passivator, where A is a large organic cation and X is a halide. These surface treatments passivate the perovskite by forming layered perovskites (e.g., A2PbX4) or by AX itself serving as a surface passivation agent on the perovskite photoactive film. It remains unclear whether layered perovskites or AX is the ideal passivator due to an incomplete understanding of the interfacial impact and resulting photoexcited carrier dynamics of AX treatment. In the present study, we use TRPL measurements to selectively probe the different interfaces of glass/perovskite/AX to demonstrate the vastly distinct interfacial photoexcited state dynamics with the presence of A2PbX4 or AX. Coupling the TRPL results with X-ray diffraction and nanoscale microscopy measurements, we find that the presence of AX not only passivates the traps at the surface and the grain boundaries, but also induces an alpha/delta-FAPbI3 phase mixing that alters the carrier dynamics near the glass/perovskite interface and enhances the photoluminescence quantum yield. In contrast, the passivation with A2PbI4 is mostly localized to the surface and grain boundaries near the top surface where the availability of PbI2 directly determines the formation of A2PbI4. Such distinct mechanisms significantly impact the corresponding solar cell performance, and we find AX passivation that has not been converted to a layered perovskite allows for a much larger processing window (e.g., larger allowed variance of AX concentration which is critical for improving the eventual manufacturing yield) and more reproducible condition to realize device performance improvements, while A2PbI4 as a passivator yields a much narrower processing window. We expect these results to enable a more rational route for developing AX for perovskite. Dou B.D., deQuilettes D.W., Laitz M., Brenes R., Wang L., Wassweiler E.L., Swartwout R., Yoo J.J., Sponsellar M., Hartono N.T.P., Sun S., Bunoassisi T., Bawendi M., Bulović V., arXiv:2203.05904 (2022) https://images.squarespace-cdn.com/content/v1/60073f823d27c928fce58f8f/bfb9edd9-2416-4e02-a3a1-fce7a2696c4a/Screen+Shot+2022-03-29+at+10.38.42+PM.png Research - Solar Technologies - Predicting Low Toxicity and Scalable Solvent Systems for High-Speed Roll-to-Roll Perovskite Manufacturing. Printed lead-based perovskite photovoltaics (PV) have gained interest due to their potential to be manufactured with scalable roll-to-roll techniques. In industrial scale-up, toxicity of inks can constrain roll-to-roll manufacturing due to the added cost of managing toxic effluents. Due to solvent toxicity, few perovskite solution chemistries in published works are scalable to gigawatt production capacity at low cost. Herein, it is shown that for scalable PV production, the use of aprotic polar solvents should be avoided due to their overall toxicity. Compliance with worldwide worker safety regulations for solvent exposure limits could require additional air handling requirements for some solvents, which in turn would affect cost-effectiveness. It is shown that costs associated with handling of hazardous substances can be significant and estimate an added cost of ¢3.7/W for dimethylformamide (DMF)-based inks. To solve this problem, a new perovskite ink solvent system is developed that is composed entirely of ether and alcohol, which has an effective exposure limit 14× higher than DMF, making it suitable for industrial coating processes. It is shown that the new ink solvent system is capable of fabricating high-efficiency perovskite solar cells processed in 1 min on a standard roll-to-roll system. Swartwout R., Patidar R., Belliveau E., Dou B., Beynon D., Greenwood P., Moody N., deQuilettes D., Bawendi M., Watson T., Bulović V., Solar RRL (2022) https://images.squarespace-cdn.com/content/v1/60073f823d27c928fce58f8f/d3d4473c-50c8-4e68-b3ca-c4a1873f4155/Screen+Shot+2022-03-29+at+10.27.57+PM.png Research - Solar Technologies - Impact of Photon Recycling, Grain Boundaries, and Nonlinear Recombination on Energy Transport in Semiconductors. A comprehensive framework for modeling energy carrier transport upon optical excitation in both excitonic and free carrier semiconductors is developed and applied. Using metal halide perovskite thin films as a model system, we demonstrate that processes such as nonlinear recombination and photon recycling can have a significant impact on the measured energy carrier profiles, especially for excitonic materials with short radiative lifetimes. Additionally, we find that film microstructure can lead to unique transport profiles that strongly depend on the material boundary behavior and the differences between the domain feature size and the energy carrier diffusion length. Our analysis provides a rigorous model of energy transport in semiconducting materials and a detailed assessment of the fundamental parameters needed for the design and optimization of electronic and optoelectronic devices. deQuilettes D.W., Brenes R., Laitz M., Motes B.T., Glazov M.M., Bulović, V., ACS Photonics 2022, 9, 1, 110–122 https://images.squarespace-cdn.com/content/v1/60073f823d27c928fce58f8f/1614113581764-4O8KGM5R1CY4NJ1O523V/Screen+Shot+2021-02-23+at+3.52.49+PM.png Research - Solar Technologies - Passivation Strategies in Emerging Photovoltaics. Despite rapid advancements in power conversion efficiency in the last decade, perovskite solar cells still perform below their thermodynamic efficiency limits. Non-radiative recombination, in particular, has limited the external radiative efficiency and open circuit voltage in the highest performing devices. We review the historical progress in enhancing perovskite external radiative efficiency and determine key strategies for reaching high optoelectronic quality. Specifically, we focus on non-radiative recombination within the perovskite layer and highlight novel approaches to reduce energy losses at interfaces and through parasitic absorption. By strategically targeting defects, it is likely that the next set of record-performing devices with ultra-low voltage losses will be achieved. deQuilettes D. W.*, Laitz M., Brenes R., Dou B., Motes B.T., Stranks S.D., Snaith H.J., Bulović V., Ginger D.S., Pure Appl. Chem. (2020) https://images.squarespace-cdn.com/content/v1/60073f823d27c928fce58f8f/1614113329036-GNQAMX7SA8BYOVSNW030/Screen+Shot+2021-02-23+at+3.47.58+PM.png Research - Solar Technologies - Photon Recycling in High-Efficiency Photovoltaics. Photon recycling is required for a solar cell to achieve an open-circuit voltage (VOC) and power conversion efficiency (PCE) approaching the Shockley-Queisser theoretical limit. The achievable performance gains from photon recycling in metal halide perovskite solar cells remain uncertain due to high variability in material quality and the nonradiative recombination rate. We quantify the enhancement due to photon recycling for state-of-the-art triple-cation perovskite films and corresponding solar cells. We show that, at the maximum power point (MPP), the absolute PCE can increase up to 2.0% in the radiative limit, primarily due to a 77 mV increase in (VMPP). For this photoactive layer, even with finite nonradiative recombination, benefits from photon recycling can be achieved when nonradiative lifetimes and external light-emitting diode (LED) electroluminescence efficiencies, QLEDe , exceed 2 μs and 10%, respectively. This analysis quantifies the significance of photon recycling in boosting the real-world performance of perovskite solar cells toward theoretical limits. Brenes R.*, Laitz M.*, Jean J., deQuilettes D.W., Bulović V., Phys Rev Applied 12, 014017 (2019) https://images.squarespace-cdn.com/content/v1/60073f823d27c928fce58f8f/1614114274216-UOSGJ260L93UCUB2EVWR/IMG_1290.jpg Research - Solar Technologies - Vapor Transport Deposition of Next-Generation Solar Materials. Current vapor-based deposition techniques for perovskite films are too slow to be cost-effective on a solar cell manufacturing line. We designed a manufacturing tool prototype that deposits perovskite films at a high rate and allows for tighter control over film formation. Using this tool, we research the fundamental film formation and device properties of vapor-deposited perovskite solar cells. We are currently recruiting new graduate students for this project! https://images.squarespace-cdn.com/content/v1/60073f823d27c928fce58f8f/1614114321882-T5CRA73KRPKN1WDPKAZD/IMG_3585.jpeg Research - Solar Technologies - Roll-to-Roll Solar Energy with Safe Solvents. Next generation thin-film solar has the potential to be incredibly low-cost, highly efficient, and reduce manufacturing CapEx – a current limitation to solar growth. In order to realize this potential, however, printing processes for solar materials must be fast (>10m/min) as well as utilize non-hazardous processes in order to be cost competitive. We have recently developed processes that allow us to easily print stable perovskite materials from low toxicity solvents at high speed. At small scale these methods have shown power conversion efficiency >20%. Improving upon these methods and fabricating mini-modules will be the key to the success of next generation solar technologies. https://www.onelab.mit.edu/research/light-sources monthly 0.5 2021-01-19 https://images.squarespace-cdn.com/content/v1/60073f823d27c928fce58f8f/5fd4554e-d470-4ebd-bbdf-0f526166bd72/Screen+Shot+2022-03-29+at+10.18.42+PM.png Research - Light Sources - Spectral Diffusion and Charge Transfer Dynamics of InP QDs­­. Quantum dots (QDs) have emerged as a leading light-emitting material, with extremely high quantum efficiencies, narrow emission linewidths, synthetic flexibility, and high operating stability. The demand for energy efficient displays utilizing environmentally-benign materials has expanded efforts beyond high-performing yet heavy metal-containing QDs towards less toxic materials with comparable optical properties. We use time-resolved optical microscopy to probe the spectrally-resolved decay dynamics of InP/ZnSe/ZnS QD thin films and light-emitting diodes (QD-LEDs) to reveal the interplay between carrier diffusion, charge transfer, and exciton dissociation in the absence and presence of external fields. We investigate wavelength-dependent energy transfer rates and quantify two energy relaxation rates corresponding to spectrally-distinct populations of mobile and immobile field-screened photogenerated or field-ionized carriers. We also study the photoluminescence (PL) quenching of QD-LEDs in reverse bias towards efficient voltage-controlled optical downconverters, informing the rational design of Cd-free, high-efficiency emitters and devices for next-gen displays. https://images.squarespace-cdn.com/content/v1/60073f823d27c928fce58f8f/1611117010722-FF4WGPTN5Q13GFNMQY4O/Screen+Shot+2021-01-19+at+11.29.56+PM.png Research - Light Sources - Anisotropic QD-LEDs. Quantum Dot Light Emitting Diodes based on Anisotropic Colloidal Heterostructures ONE Lab: Giovanni Azzellino, Vladimir Bulović Collaborators: Igor Coropceanu, Moungi G. Bawendi Additional emergent properties in quantum dot LEDs can be attained by changing the shape of these nanostructured materials, such as by transitioning from spherical quantum dots to elongated structures called nanorods (NRs). A key feature that distinguishes nanorods from quantum dots is that the former emit light with a high degree of linear polarization oriented along their long axis. By orienting nanorods parallel to the substrate, the preferential emission of light perpendicular to the plane of the substrate will automatically reduce outcoupling losses, thus allowing higher external quantum efficiencies than can be achieved with QDs in conventional devices. Moreover, by aligning the nanorods in a particular direction, a simple scheme for the fabrication of polarized LEDs can be developed. Figure: TEM of self-aligned CdSe-CdS nanorods drop casted on glass https://images.squarespace-cdn.com/content/v1/60073f823d27c928fce58f8f/1611117062655-FMCSABZYZCY35NXFJ5IO/Screen+Shot+2021-01-19+at+11.30.52+PM.png Research - Light Sources - Inkjet Printing of QD-LEDs. Inkjet Printing High-Resolution Patterning of Quantum Dot LEDs ONE Lab: Giovanni Azzellino, Vladimir Bulović Collaborators: Francesca S. Freyria, Igor Coropceanu, Moungi G. Bawendi The high luminescence efficiency and uniquely size-tunable color of solution-processed semiconducting colloidal quantum dots (QDs) make them promising candidates as optically- and electrically-excited luminophores in energy-efficient, substrate-independent, high-color-quality solid-state lighting and thin-film display technologies. Recent advances in the design of electrically-driven QD-LEDs have pushed their external quantum efficiencies toward 20%, comparable to those of phosphorescent organic LEDs. However, the path of these devices to market is hampered by the difficulty of patterning the emissive quantum-dot layer. Existing prototypes are manufactured by spin-coating the colloidal QDs. Furthermore, the thermal budget of these materials remains low—heating them up decreases their photoluminescence efficiency. Given all of these constraints, inkjet printing is a good candidate for making patterned QD-LEDs. This technology offers a new and unexplored technique for room-temperature, maskless patterning of quantum dot light-emitting devices. In this project, we exploit droplet-on-demand inkjet technology to manufacture electroluminescent devices. We adopt both surface treatments and solvent engineering approaches to get rid of the “coffee-stain” effect and to deploy uniform and continuous spots of emissive quantum dots with a lateral resolution of ~10µm, using single-droplet print with a commercial inkjet printer. In addition, with the latest generation of hybrid QD-LED architectures, we show that both visible- and near-infrared-emitting QD-LEDs can be patterned with inkjet technology. We believe this work can open the door to high-resolution QD-LED displays. Figure: Optical profilometry of an array of infrared core-shell PbS-CdS quantum dots inkjet-printed onto ZnO (scale bar is 50 μm) https://www.onelab.mit.edu/research/nanomechanics monthly 0.5 2021-01-20 https://images.squarespace-cdn.com/content/v1/60073f823d27c928fce58f8f/aa67c90c-23e1-49f5-8f22-8e40b5e95d95/Screen+Shot+2022-03-29+at+10.43.48+PM.png Research - Nanomechanics - An Ultra-Thin Flexible Loudspeaker Based on a Piezoelectric Micro-Dome Array. Ultra-thin, lightweight, high-performance, low-cost and energy-efficient loudspeakers that can be deployed over a wide area have become increasingly attractive to both traditional audio systems and emerging applications such as active noise control and immersive entertainment. In this paper, a thin-film loudspeaker is proposed based on an active piezoelectric layer embossed with an array of microscale domes. Actuation of these freestanding domes contributes to excellent sound generation by the loudspeaker, for example, 86 dB sound pressure level (SPL) at 30-cm distance with 25-V (RMS) excitation at 10 kHz, regardless of the rigid surface on which it is bonded. The acoustic performance is further tunable by designing the dome dimensions. The proposed loudspeaker also exhibits high bandwidth, which extends its prospects into the ultrasonic range. The loudspeaker weighs only 2 g, is 120 μm thick and can be manufactured at low cost. These advantages make the proposed loudspeaker a promising candidate for ubiquitous applications in existing and emerging industrial and commercial scenarios. Han J., Lang J.H., Bulović V., IEEE Transactions on Industrial Electronics (2022) https://images.squarespace-cdn.com/content/v1/60073f823d27c928fce58f8f/1611116786440-MBMDBK6YE0SH8NKQT1IR/Screen+Shot+2021-01-19+at+11.25.56+PM.png Research - Nanomechanics - Molecular Platform for Fast Low-Voltage Nanoelectromechanical Switching. The use of molecules as active components to build nanometer-scale devices inspires emerging device concepts that employ the intrinsic functionality of molecules to address longstanding challenges facing nanoelectronics. Using molecules as controllable-length nanosprings, here we report the design and operation of a nanoelectromechanical (NEM) switch which overcomes the typical challenges of high actuation voltages and slow switching speeds for previous NEM technologies. Our NEM switches are hierarchically assembled using a molecular spacer layer sandwiched between atomically smooth electrodes, which defines a nanometer-scale electrode gap and can be electrostatically compressed to repeatedly modulate the tunneling current. The molecular layer and the top electrode structure serve as two degrees of design freedom with which to independently tailor static and dynamic device characteristics, enabling simultaneous low turn-on voltages (sub-3 V) and short switching delays (2 ns). This molecular platform with inherent nanoscale modularity provides a versatile strategy for engineering diverse high-performance and energy-efficient electromechanical devices. Han J., Nelson Z., Chua M.R., Swager T.M., Niroui F., Lang J.H., Bulović, V., Nano Letters, 2021, 21, 24, 10244-10251 https://images.squarespace-cdn.com/content/v1/60073f823d27c928fce58f8f/1611116715329-I9037A0U934COIHAQEJ7/Screen+Shot+2021-01-19+at+11.24.46+PM.png Research - Nanomechanics - Low-Voltage Switches. Low-Voltage and Stiction-Free Nanoelectromechanical Squitches Farnaz Niroui, Mayuran Saravanapavanantham, Annie Wang, Vladimir Bulović Collaborators: Ellen Sletten, Wen Jie Ong, Timothy Swager, Jeffrey Lang Nanoelectromechanical (NEM) switches have emerged as a promising competing technology to the conventional complementary metal-oxide semiconductor (CMOS) transistors. NEM switches can exhibit abrupt switching behavior with large on-off current ratios and near-zero off-state leakage currents. However, they typically require large operating voltages exceeding 1 V and suffer from failure due to stiction. To address these challenges, we propose an electromechanical switch, referred to as a “squitch”, based on a switching gap composed of a molecular film sandwiched between conductive contacts. In this design, an applied voltage between the electrodes provides sufficient electrostatic force to compress the molecular film. As the molecules are compressed, the distance between the electrodes is reduced, causing an exponential increase in the tunneling current to turn on the device. The molecular layer helps formation of nanoscale switching gaps that promote lowering of the actuation voltage. Concurrently, the elastic restoring force in the compressed molecular film helps overcome surface adhesive forces during operation to prevent stiction-induced failure. Related publications and links F. Niroui, A.I. Wang, E. M. Sletten, Y. Song, J. Kong, E. Yablonovitch, T. M. Swager, J. H. Lang, and V. Bulović, “Tunneling Nanoelectromechanical switches based on compressible molecular thin films,” ACS Nano, vol. 9, 7886-7894 (2015). F. Niroui, E.M. Sletten, P.B. Deotare, A.I. Wang, T.M. Swager, J.H. Lang, and V. Bulović, “Controlled fabrication of nanoscale gaps using stiction,” in Proc. 28th IEEE International Conference on Micro Electro Mechanical Systems (MEMS), 85-88 (2015). F. Niroui, P.B. Deotare, E.M. Sletten, A.I. Wang, E. Yablonovitch, T.M. Swager, J.H. Lang, and V. Bulović, “Nanoelectromechanical tunneling switches based on self-assembled molecular layers,” in Proc. 27th IEEE International Conference on Micro Electro Mechanical Systems (MEMS), 1103-1106 (2014). https://images.squarespace-cdn.com/content/v1/60073f823d27c928fce58f8f/1611116786440-MBMDBK6YE0SH8NKQT1IR/Screen+Shot+2021-01-19+at+11.25.56+PM.png Research - Nanomechanics - Electrically Tunable Lasers. Electrically Tunable Organic Vertical-Cavity Surface-Emitting Lasers Wendi Chang, Apoorva Murarka, Annie Wang, Vladimir Bulović Since their invention in the 1950s, laser systems are an example of a ubiquitous technology that enabled a wide range of applications. From Blu-ray to surgeries, lasers also created the foundation of the modern field of photonics and spectroscopy. However, creating a compact, dynamically tunable laser in the visible wavelengths is still an undeveloped problem. A wavelength tunable lasing device would enable many fields of research and technology, including spectroscopy and remote sensing. Laser wavelength tuning using standard nonlinear optics techniques requires high power and large equipments. While small compact lasers with a range of visible emission wavelengths has been fabricated on a single device, the emission is predetermined during fabrication and cannot be dynamically tuned. Drawing inspiration from developments in micro-electro-mechanical systems (MEMS) of tunable inorganic, infrared lasers, we demonstrate a organic vertical-cavity surface-emitting laser (VCSEL) with dynamic wavelength-tunability in the visible wavelengths. Since standard inorganic semiconductor fabrication methods such as lithography and etching cannot be applied to soft, organic materials, we develop a composite membrane contact-transfer printing technique to fabricate an array of microcavities. Each vertical cavity is formed by a bottom DBR substrate and a suspended top silver mirror. By applying a voltage across top gold contact and bottom indium tin oxide (ITO) electrode, electrostatic pressure deflects the top membrane, changing the cavity length and laser emission wavelength. Beyond tunable lasing, the same device in could enable many applications as an all-optical pressure sensing array, where the cavity length change is correlated with pressure difference across each membrane. Figure: (a) Schematic of device structure; voltage applied between the top gold and bottom ITO allows membrane deflection due to electrostatic force. (b) Optical interferometry difference image between 20V and 0V applied bias on an array of devices as imaged from the top membrane. (c) Comparison of cavity mode emission peak shift with membrane deflection. (d) Difference profile between applied bias and 0V bias show controllable membrane deflection. Related publications and links W. Chang*, A. Murarka*, A. Wang*, G. M. Akselrod, C. Packard, J. Lang, and V. Bulovic, “Electrically tunable organic vertical-cavity surface-emitting laser,” Appl. Phys. Lett., 105, 073303 (2014). W. Chang*, A. Wang*, A. Murarka*, J. Lang, and V. Bulovic, "Transfer-Printed Composite Membranes for Electrically-Tunable Organic Optical Microcavities,” Micro Electro Mechanical Systems (MEMS), 2014 IEEE 27th International Conference on. https://www.onelab.mit.edu/research/excitonics monthly 0.5 2021-01-20 https://images.squarespace-cdn.com/content/v1/60073f823d27c928fce58f8f/2fdb04aa-3ec7-47d8-aa48-7ae871ddd783/Screen+Shot+2022-03-29+at+9.55.43+PM.png Research - Excitonics - Perovskite Microcavity Exciton-Polaritons. Laitz et al., Uncovering Temperature-Dependent Exciton-Polariton Relaxation Mechanisms in Perovskites, arXiv:2203.13816 (2022) The fundamental challenge in realizing all-optical transistors is that light is weakly interacting. While it is difficult to have one photon influence the behavior of another, it is possible to make interacting quasi-particles called polaritons that have characteristics of both photons and excitons – both light and matter. Polaritons are formed in optical microcavities in the strong coupling regime between bound excitons and cavity photons. This quantum superposition results in a half-light, half-matter bosonic quasi-particle. Polaritons can be tuned to adjust the fraction of photonic or excitonic features, so that, even when mostly photonic, polaritons have a finite interaction strength, resuling in the potential for engineering fast, low-loss, low-power all-optical transistors. Additionally, these properties establish opportunities for studying out of equilibrium Bose Einstein condensation, super-fluidity and quantum vortices for low-threshold polariton lasing. Traditionally, polaritons have been formed in all-inorganic semiconducting materials (e.g. GaAs heterostructures) which require low operating temperatures (4-70 K) for polariton formation to ensure the exciton binding energy is above kT and the strong coupling interaction is faster than the exciton dissipation rate. The solution appears to lie in a material candidate that has been traditionally employed in photovoltaics. Hybrid perovskites have emerged as a leading active layer material in high efficiency single junction photovoltaics, now surpassing all other thin-film technologies in performance with a certified power conversion efficiency exceeding 25%. We have demonstrated room-temperature exciton-polariton formation in metallic cavities, probed by angle resolved reflectivity and PL measurements through a k-space imaging setup. In the referenced work, we perform temperature-dependent measurements of polaritons in low-dimensional hybrid perovskite microcavities and demonstrate high light-matter coupling strengths with a Rabi splitting of 260 ± 5 meV. By embedding the perovskite active layer near the optical field antinode of a wedged microcavity, we are able to tune the Hopfield coefficients by moving the optical excitation along the wedge length and thus decouple the primary polariton relaxation mechanisms in this material for the first time. We observe the thermal activation of a bottleneck regime, and reveal that this effect can be overcome by harnessing intrinsic scattering mechanisms arising from the interplay between the different excitonic species, such as biexciton-assisted polariton relaxation pathways, and isoenergetic intracavity pumping. We demonstrate the dependence of the bottleneck suppression on cavity detuning, and are able to achieve efficient relaxation to k|| = 0 even at cryogenic temperatures. This new understanding contributes to the design of ultra-low-threshold BEC and condensate control by engineering polariton dispersions concomitant with efficient relaxation pathways, leveraging intrinsic material scattering mechanisms for next-generation polariton optoelectronics. https://images.squarespace-cdn.com/content/v1/60073f823d27c928fce58f8f/1611116328151-HC2XXBTQFCK6G2ONX5M2/Screen+Shot+2021-01-19+at+11.18.37+PM.png Research - Excitonics - Stabilizing J-Aggregates. Organic molecules, such as J-aggregated cynanine dyes are promising candidates for forming exciton-polaritons in high quality factor microcavities due to their unmatched high oscillator strengths, narrow emission linewidths at room temperature (FWHM ~ 12 nm), and small Stokes shift. Previously limited by poor stability, we recently demonstrated a marked improvement in the damage thresholds by suspending them in a hydrophobic trehalose/sucrose sugar matrix. In addition to having a wide range of molecules that form aggregates with different structural backbones, we can control the aggregation and electronic properties of these molecules through solution chemistry which can be preserved and directly transferred to the solid state. Figure: Photoluminescence dispersion curve of lower polariton branch formed with J-aggregates showing preferential emission at higher energy and momentum possibly due to incompatible energy and momentum requirements for further relaxation through vibronic coupling.