Over 12% Efficient CuIn(S,Se)2 Solar Cell with the Absorber Fabricated from Dimethylformamide Solution by Doctor‐Blading in Ambient Air

Abstract

Solution‐processed chalcopyrite copper indium gallium sulfoselenide (Cu(In,Ga)(S,Se)2, CIGSSe) thin‐film solar cells have achieved efficiency beyond 18% and have great potential as an alternative to vacuum‐based ones. However, most of the efficient solution‐based CIGSSe solar cells are fabricated by spin‐coating in an inert atmosphere, which limits the transfer from lab protocol to industrial large‐scale production. Herein, a scalable doctor‐blading technique is applied to fabricate CuIn(S,Se)2 (CISSe) absorbers from N,N‐dimethylformamide molecular precursor solution in ambient air. With the optimization of the precursor concentration to reduce the residue solvent and change the thermal annealing process from one‐step to two‐step to separate solvent evaporation and complex decomposition to suppress fluidity, high‐quality absorber films with densely packed large grains have been fabricated and a champion CISSe solar cell with a power conversion efficiency of 12.54% has been achieved. Importantly, unlike the spin‐coating technique which may cause composition change due to the different solubilities of the precursors, the doctor‐bladed film has a composition very close to the precursor solution, which is very important for precise control of the absorber composition for industrial production.