Over 10% Efficient CuIn(S,Se)2 Solar Cells Fabricated From Environmentally Benign Solution in Air

A safe and environmentally benign solvent is a requisite for mass production of thin film solar cells via solution methods. Here, a highly industry suitable solvent N ‐methyl‐pyrrolidone (NMP) is used for the first time to make a precursor solution with simple compounds of CuCl, InCl 3 ·4H 2 O and thiourea and fabricate CuIn(S,Se) 2 (CISSe) solar cells. A power conversion efficiency of 10.23% has been achieved from the NMP‐based solution when the precursor film was processed in air, which is only 8.55% for film processed in glove box. Characterizations using XRD, Raman, SEM, EDX, and FTIR show air annealing favors decomposition of organic species in the precursor film, which results in high quality absorber materials. Further improvement in device efficiency can be expected by gallium alloying and optimization of device fabrication conditions. The results demonstrate highly efficient thin film solar cells can be fabricated from an industry suitable NMP precursor solution in air, which is promising for simplifying film processing and reducing manufacture cost.