Over 16% Efficient Solution‐Processed Cu(In,Ga)Se₂ Solar Cells via Incorporation of Copper‐Rich Precursor Film

Abstract Solution processing of Cu(In,Ga)Se₂ (CIGS) absorber is a highly promising strategy for a cost‐effective CIGS photovoltaic device. However, the device performance of solution‐processed CIGS solar cells is still hindered by the severe non‐radiative recombination resulting from deep defects and poor crystal quality. Here, a simple and effective precursor film engineering strategy is reported, where Cu‐rich (CGI >1) CIGS layer is incorporated into the bottom of the CIGS precursor film. It has been discovered that the incorporation of the Cu‐rich CIGS layer greatly improves the absorber crystallinity and reduces the trap state density. Accordingly, more efficient charge generation and charge transfer are realized. As a result of systematic processing optimization, the champion solution‐processed CIGS device delivers an improved open‐circuit voltage of 656 mV, current density of 33.15 mA cm⁻², and fill factor of 73.78%, leading to the high efficiency of 16.05%.