Influence of the Se environment on Cu-rich CIS devices

Besides their better electronic properties, Cu-rich CuInSe2 solar cells performed worse than the Cu-poor ones. Dominated by interface recombination which lowers their open circuit voltage, they also exhibit lower current. They are indeed limited by a high native doping which leads to tunneling enhanced recombination. In order to decrease this doping, we investigate the effect of the selenium environment during the absorber growth. We demonstrate that the chemical activity of the Se during the growth strongly influences both the film microstructure and the solar cell performance via various structural and opto-electronic characterization on both the absorber and the resulting solar cells: scanning electron microscopy, energy dispersive X-ray spectrometry, X-ray diffraction in addition to classical current–voltage and quantum efficiency measurements on the solar cell devices. We show that low Se environment is beneficial to obtain better Cu-rich solar cells.