Investigation of Varying Se Vapor Pressure During Deposition of CdSeTe Thin Film PV Devices

Polycrystalline CdSeTe (CST) thin film material has shown External Radiative Efficiency (ERE) as high as 6% and carrier lifetimes as high as 4 microseconds measured using TRPL. However, resultant CST-only absorber devices exhibit poor cell performance. Due to the higher vapor pressure (V-p) of Se in comparison to Cd and Te, CST films are likely to have Se vacancies. Normalized emission reconstructed from PL exhibits low energy emission peak suggesting sub-bandgap features in CST. Device modeling using SCAPS 1-D suggests low hole mobility in CST. In this work, the role of vacancy Se (V-Se) that may be responsible for the low energy emission peak and poor carrier mobility in CST-only absorber devices is being investigated.