Low band‐gap CuIn(S,Se) 2 thin film solar cells using molecular ink with 9.5% efficiency (Phys. Status Solidi C 6/2017)

In order to achieve low band-gap thin film solar cells which can play an important role in tandem solar cells combined with perovskite top solar cells, the preparation of chalcopyrite absorbers is a major task. Wang et al. (article no. 1600169) report a non-vacuum simple solution coating approach for CuIn(S,Se)2 absorbers using an air stable molecular ink containing metal chlorides and thiourea in organic solvents. Careful balancing of ink concentration, number of precursor deposition cycles, and annealing temperature profile will transform the multilayer precursor into a sufficiently thick, continuous, large grained film as required for high quantum efficiency, and good red response of the cells. These optimizations aimed at high photo current have already led to an efficiency of 9.5% at a band-gap of 1.02 eV.