Electronic Properties of CdS/CdTe Solar Cells as Influenced by a Buffer Layer

TL;DR

This study investigates how different buffer layers affect the electronic defect states in CdTe solar cells, revealing that buffer material choice influences doping efficiency and recombination centers, with strain and chlorine interactions playing key roles.

Contribution

It demonstrates that buffer layer material impacts defect density and electronic properties in CdTe solar cells, highlighting the role of strain and chlorine interactions in defect formation.

Findings

ZnSe and ZnS buffer layers reduce ionized acceptor concentration

Deep trap levels shift to midgap with certain buffer layers

Strain influences defect interactions at grain boundaries

Abstract

We considered modification of the defect density of states in CdTe as influenced by a buffer layer in ZnO(ZnS, SnSe)/CdS/CdTe solar cells. Compared to the solar cells employing ZnO buffer layers, implementation of ZnSe and ZnS resulted in the lower net ionized acceptor concentration and the energy shift of the dominant deep trap levels to the midgap of CdTe. The results clearly indicated that the same defect was responsible for the inefficient doping and the formation of recombination centers in CdTe. This observation can be explained taking into account the effect of strain on the electronic properties of the grain boundary interface states in polycrystalline CdTe. In the conditions of strain, interaction of chlorine with the grain boundary point defects can be altered.