• Electronics
• Micro Power Sources
• Microsystem Integration & Packaging
• Optoelectronic Devices
• Quantum Dot, Organic, & Flexible Electronics
• Sensor Power & Packaging Technologies
• Sensors & Systems
• Thermal Management

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Optoelectronic and Photovoltaic Devices

Our engineers conduct research and development of optoelectronic, photovoltaic, and high-speed devices in Group III-V and Group IV materials. In support of this work, we develop and apply high-performance compound semiconductor materials, novel device processing methods, and careful characterization methods such as quantum-efficiency and device I-V measurements.

We have the ability to grow a variety of materials in Group IV, Group III-V, Group II-VI, as well as Group V-VI systems and on a variety of substrates. We routinely grow complex structures such as superlattices, nanodots, and quantum dots in our laboratories and work closely with various collaborators to process these structures into high-performance devices.

Inorganic Photovoltaics

Our expertise in solar cells dates back to the 1980s, when our scientists, in collaboration with researchers at North Carolina State University, pioneered the first tunnel-junction cascade solar cells in the GaAs-AlGaAs materials system. This set the stage for the development of GaInP2-GaAs cascade solar cells in early 1990s by the National Renewable Energy Laboratory.

We also developed the first p-on-n GaInP2-GaAs-Ge, 3-junction cascade solar cell that was transitioned to industry for further advancement and large-scale manufacturing. This technology is being used in modern satellites.

Today, we are researching Si, SiGe alloy, Si/Ge superlattice, Si/Ge quantum dot solar cells through an innovative combination of nanoscale materials, device structures, and processing, along with the use of surface plasmonics to enhance long wavelength photon absorption. Working with Duke University researchers who are developing organic solar cells, we are investigating the integration of low-cost inorganic solar cells to form hybrid inorganic-organic photovoltaic structures that are 15% more efficient than current technology.

Related Research

• Nanoparticles, Nanotubes, and Quantum Dots

Research Citations

• Barletta P, G Dezsi, L Lee, R Venkatasubramanian (2010). SiGe/Si nanodot superlattices for Si-based solar cells. Proceedings of the IEEE Southeast Conference 2010, March 18-21, 2010, Charlotte, NC.
• ML Lee, G Dezsi, R Venkatasubramanian (2010). Analysis of SiGe/Si quantum dot superlattices grown by low-pressure chemical vapor deposition for thin solar cells. Thin Solid Films 518:S76–S79.
• AK Sood, RA Richwine, YR Puri, N DiLello, JL Hoyt, TI Akinwande, S Horn, RS Balcerak, G Bulman, R Venkatasubramanian, AI D'Souza, TG Bramhall (2009). Development of low dark current SiGe-detector arrays for visible-NIR imaging sensor. Proceedings of the SPIE, 7298 (72983D).
• R Kurtz, K Alim, R Pradhan, V Esterkin, G Savant, R Venkatasubramanian, ML Lee, S Ghosh, I Calizo, A Balandin (2007). High-speed nano-optical photodetector for free space communication. Proceedings of the SPIE, 6556 (65560H).
• Venkatasubramanian R., O'Quinn BC, Siivola E, Keyes B, Ahrenkiel R (1997). 20% (AM1.5) efficiency GaAs solar cells on sub-mm grain-size poly-Ge and its transition to low-cost substrates. Twenty Sixth IEEE Photovoltaic Specialists Conference, Anaheim, CA, 29 September - 03 October 1997, 811-814.
• Lasich JB, Cleeve A, Kaila N, Ganakas G, Timmons M, Venkatasubramanian R, Colpitts T, et al. (1994). Close-packed cell arrays for dish concentrators. IEEE First World Conference on Photovoltaic Energy Conversion, Conference Record of the Twenty Fourth IEEE Photovoltaic Specialists Conference - 1994 : Waikoloa, Hawaii, December 5-9, 1994., (2):1938-1941.
• Venkatasubramanian R, Timmons ML, Hutchby JA, Field H, Emery K (1994). GaAs and Al0.2Ga0.8As solar cells with an indirect-bandgap Al0.8Ga0.2As emitter-heterojunction cells. IEEE First World Conference on Photovoltaic Energy Conversion, conference record of the Twenty Fourth IEEE Photovoltaic Specialists Conference - 1994 : Waikoloa, Hawaii, December 5-9, 1994, (2):183921842.
• Venkatasubramanian R, Timmons ML, Colpitts TS, Hancock J, Hills J, Hutchby JA, et al. (1993). Development of high-efficiency Al0.2Ga0.8As solar cells and interconnect schemes for Al0.2Ga0.8As/Si mechanically-stacked cascade cells. Twenty Third IEEE Photovoltaic Specialists Conference--1993, Louisville, KY, May 10-14, 1993, 752-756.
• Venkatasubramanian R (2000). Low-temperature chemical vapor deposition and etching apparatus and method. U.S. Patent No. 6,071,351. Washington, D.C.: U.S. Patent and Trademark Office.