Direct-ink coating techniques for Cu-based multicomponent semiconductor films

Thin film solar cells based on earth-abundant, non-toxic multicomponent chalcogenides have the potential to deliver cost-competitive solution for large-scale deployment. Direct deposition of new materials has been vigorously investigated to improve the device efficiency. In this paper, we report direct ink coating of Cu-based multicomponent solar absorber materials such as CuCdS2 (CCdS), Cu2CoSnS4 (CCoTS) and Cu2FeSnS4 (CFTS) in methanol and ethylene glycol. Films were first dried at 110 degrees C for 10 min. The precursor films were then heated at 200 degrees C in air for 20 min to achieve final crystalline phase. Structural and microstructural properties of the films deposited from methanol revealed that these films are compact and void free. However, films are comparatively rough and porous in case of ethylene glycol. The direct optical band gaps of CCdS, CCoTS and CFSTS films are 2.43, 1.3 and 1.4 eV, respectively. The electrical measurements reveal that the films have p-type conduction and are promising absorber materials for photovoltaic applications.