Nanostructured Enhanced Photovoltaics
Solar energy is one of the major forms of renewable energy. The demand for high performance and low cost solar cells has continuously driven the research on photovoltaics for decades. Here we are employing self-assembled 3-D nanostructures to improve the performance of the solar cells.  The 3-D architecture can  improve light absorption, resembling the naturally formed forest to harvest light. Meanwhile, the increased junction area facilitates carrier collection, which is particularly beneficial for PV devices made of materials with low surface recombination velocity.




Nanophotonics is the study of the behavior of light on the nanometer scale. It is crucial to understand light-matter interaction at nanoscale for rational design of efficient photonic and optolectronic devices with nanostructures and nanomaterials. In our work, we have fabricated a variety of 3-D nanophotonic structures, including nanopillar (NPL) arrays, Nanospike (NSP) arrays, Nanowell (NWL) arrays, etc., with lithography-free approaches. We have been able to engineer shape, geometry and ordering of the materials to tune their optical properties. These materials are potential candidates for novel optolectronic devices, including solar cells, lasers, photodetectors, etc.


Large-scale Integrated Nanowire Electronics

Semiconductor nanowires have been extensively explored as the potential building blocks for a variety of electronic and optoelectronic applications due to the continuous increased demand for miniaturized devices and circuits. However, controlled and uniform assembly of “bottom-up” nanowire (NW) materials with high scalability is one of the major bottleneck challenges towards the integration of nanowires for circuit applications. We have achieved wafer-scale assembly of highly ordered arrays of NWs through a simple contact printing method. With this generic approach, a wide range of semiconductor NWs have been successfully assembled at large-scale and configured as a variety of functional electronic and optoelectronic devices, including transistors, diodes and sensors on rigid and flexible substrates. Furthermore, these functional components are integrated together and an all-nanowire image sensing circuit is realized.


High Performance Sensing with Semiconductor Nanowires

NWs are ideal candidates for chemical and biological sensing due to 1) chemically active surfaces and large surface-to-volume ratio; 2) the radius being comparable to the Debye screening length thus resulting in the dominant role of surface electrostatics on the carrier conduction through the entire material. To date, researchers have developed a wide range of chemical and biological sensors based on single and arrayed NWs; in some cases with higher detection sensitivity than their thin film counterparts. We have investigated chemical/gas sensing targeting O2, NO2, CO, NH3, using materials including ZnO and Si nanowires.




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