Nanoscale Imaging and Spectroscopy of Band Gap and defects in Polycrystalline Photovoltaic Devices

Published

April 12, 2017

Author(s)

Yohan Yoon, Jungseok Chae, Aaron M. Katzenmeyer, Heayoung Yoon, Joshua D. Schumacher, Sang M. An, Andrea Centrone, Nikolai B. Zhitenev

Abstract

Improving the power conversion efficiency of photovoltaic (PV) devices is challenging because the generation, separation and collection of electron-hole pairs in PV devices is strongly dependent on details of the nanoscale chemical composition and defects which are often poorly known. In this work, two novel scanning probe nano-spectroscopy techniques, direct-transmission near-field scanning optical microscopy (dt-NSOM) and photothermal induced resonance (PTIR), are implemented to determine the distribution of defects and the bandgap variation in thin lamellae extracted from polycrystalline CdTe PV devices. dt-NSOM provides high-contrast spatially- resolved maps of light transmitted through the sample at selected wavelengths. PTIR provides absorption maps and spectra over a broad spectral range, from visible to mid-infrared. Results show variation of the bandgap through the CdTe thickness and from grain to grain that is spatially uncorrelated with the distributions of shallow and deep defects, likely related to the diffusion of impurities from the back contact.

Citation

Nanoscale

Volume

9

Pub Type

Journals

Download Paper

https://doi.org/10.1039/C7NR01480E

Keywords

direct-transmission near-field scanning optical microscopy (dt-NSOM), photothermal induced resonance (PTIR), CdTe, bandgap, deep defects, spectroscopy, photovoltaic (PV)

Citation

Yoon, Y. , Chae, J. , Katzenmeyer, A. , Yoon, H. , Schumacher, J. , An, S. , Centrone, A. and Zhitenev, N. (2017), Nanoscale Imaging and Spectroscopy of Band Gap and defects in Polycrystalline Photovoltaic Devices, Nanoscale, [online], https://doi.org/10.1039/C7NR01480E (Accessed October 9, 2025)