Influence of Ga content on defects in CuInxGa1 − xSe2 based solar cell absorbers investigated by sub gap modulated photocurrent and admittance spectroscopy

In this work, we investigate the influence of gallium content on the defects properties of co-evaporated CuInxGa1 − xSe2 by sub gap modulated photocurrent spectroscopy and admittance spectroscopy techniques. A series of CuInxGa1 − xSe2 based solar cells with different gallium content in the range from 0% to 33%, and with the same CdS buffer layer have been investigated. On one hand, photocurrent spectroscopy results show 2 types of defects named D1 and D2, and on the other hand, admittance spectroscopy results exhibit only one type of defect. I–V curves show that one of the two defects probed by photocurrent is responsible of the dominant recombination mechanisms next to the heterointerface, between the absorber and the buffer layers. Moreover, I–V curves under AM 1.5 conditions show that the cell with no probed D2 defect presents the best photovoltaic performances.