Buffer free Cu In,Ga Se2 solar cells by near surface ion implantation

Abstract

High efficiency Cu In,Ga Se2 thin film solar cells typically include CdS buffer layers deposited in a chemical bath. In this work, Cu In,Ga Se2 devices are presented in which the CdS buffer layer was omitted completely. Instead, low energy ion implantation of group II elements Cd, Zn, and Mg is applied in order to establish an n type surface layer in p type Cu In,Ga Se2 absorber layers. Therefore, thermal annealing procedures were developed which lead to a full recovery of the implantation induced defects and simultaneously minimize the diffusion of the dopants. Such a treatment is shown to provide high quality p n junction functionality and buffer free Cu In,Ga Se2 thin film solar cells with opencircuit voltages close to 600 mV and efficiencies exceeding 1