Bias dependent admittance spectroscopy: the impact of sodium supply on the Cu(In,Ga)Se2 growth

Abstract

In modern Cu(In,Ga)Se2 (CIGS) solar cell production, alkali-poor substrates are becoming increasingly common. Thus, understanding the effect of alkali atoms on the growth of the CIGS absorber has become crucial. We studied this impact by comparing the bias dependent admittance spectroscopy response of CIGS solar cells grown with varying amounts of sodium using two different growth processes. The absence of sodium led to an intense response which is progressively replaced by other response domains as the sodium supply increases. We linked these new domains to Na accumulation and a resulting increase in band bending at the CIGS/CdS interface.