“Nano-Engineering of Photovoltaic Devices”

By Dr. Heayoung Yoon, Research Associate, Center for Nanoscale Science & Technology, National Institute of Standards & Technology (NIST)

Friday, April 24th, 2015 from 3:05 – 3:55 p.m. in WEB 1230


Significant progress has been made in solar energy harvesting and conversion technology using inexpensive photovoltaic (PV) materials. Among these materials, cadmium telluride (CdTe) and copper indium gallium selenide (CIGS) solar cells represent one of the most successful PV technologies on the market today, currently reaching a power conversion efficiency of 21.5 % and 21.7 %, respectively. To achieve the maximum efficiency of 30 % possible for these technologies, considerable efforts have been made to understand the physical mechanisms that limit cell performance. In this talk, I present the inhomogeneous microstructural properties of CdTe solar cells in correlation with their macro-scale device performance. For quantitative determination of local photovoltaic properties at the nanoscale, electron-hole pairs are generated by either near-field optical illumination or low energy electron beam excitation. The spatially and spectrally resolved photocurrent maps confirm high carrier collection efficiencies at grain boundaries. An analytical model is introduced, and the extract material parameters at the level of single grains are compared. I outline future directions for low cost, high efficiency thin film solar cells by engineering their microstructures, surface, and interface.


Heayoung P. Yoon is a researcher associate in the Center for Nanoscale Science and Technology at National Institute of Standards and Technology (NIST). She received her B. S. and M. S. in Physics (minor: Computer Science) from Chungnam National University and Pohang University of Science and Technology in South Korea. She worked at the Samsung Advanced Institute of Technology before entering graduate school at Penn State. She received a Ph. D. in Electrical Engineering at Penn State, where her research focused on nanofabrication and integration of molecular junction devices. She continued postdoctoral research at Penn State on micro/nanowire solar cells. In the CNST at NIST, she is working on development of nanoscale measurement techniques for solar cells, hybrid nanomaterials and nanoelectronics devices.