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

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.