Carbon-nanofibers film as a back-contact buffer layer in CdTe thin film solar cell

Carbon nanofibers (CNFs) based thin films were introduced as a buffer layer in the back contact of of CdTe thin film solar cells. CNFs buffer layer is used to replace the conventional metal contact layer. Quantitative band alignment measurement by using X-ray photoelectron spectroscopy (XPS) demonstrated that a relatively low energy barrier at the CNF/CdTe interface was formed. The valance band offset of 0.47 eV and conduction band offset of 0.80 eV were examined between CNF and CdTe. The stability of CdTe solar cells was considerably improved by introducing CNF buffer layer with trace amount of Cu to fabricate low-energy barrier back contact. The CNFs as a buffer layer between CdTe and metal Au electrode based fabricated CdTe thin film solar cells demonstrated a conversion efficiency of 11.4 %. From the device stability stressing tests we conclude that CNFs as a buffer layer in a CdTe thin film solar cell meaningfully improved the cell performance and device stability.