Properties of CuSbS2 thin films electrodeposited from ionic liquids as p-type absorber for photovoltaic solar cells

• CuSbS2 films electrodeposited in choline chloride–urea ionic liquid for solar cells
• CuSbS2 films electrodeposited in single phase chalcostibite structure at − 0.65 V vs Pt
• Precursors Cu/Sb (1:0.71) and (1:1.4) led to Cu3SbS3 and Sb2S3 phases, respectively.
• CuSbS2 films show direct 1.66 eV band gap consistent with density function calculations.
• CuSbS2 films form heterojunction in nZnO–pCuSbS2 structure useful for solar cells.

Electrodeposition of CuSbS2 semiconductor thin films for photovoltaic solar cells is investigated from ionic liquid electrolyte based on choline chloride–urea eutectic. Cyclic voltammetry study shows Cu and Sb deposition potential of − 0.54 V and − 0.48 V vs Pt, respectively. Highly crystalline CuSbS2 films in the chalcostibite orthorhombic structure without binary compound phases are electrodeposited at a potential of − 0.65 V vs Pt with Cu to Sb precursor ratio of 1:1 and Na2S2O3 as sulfur source in ionic liquid medium held at 80 °C. Increase in Cu-precursor ratio (1:0.71) led to Cu3SbS3 ternary and that of Sb-precursor ratio (1:1.4) led to binary Sb2S3 phase inclusion in the phase field of the CuSbS2 films. Electrochemical impedance spectroscopy studies show diffusive ionic transport limited growth mechanism. Single phase CuSbS2 films show direct band gap energy of 1.66 ± 0.01 eV and films with inclusive secondary phases have band gap energy of 1.73 ± 0.01 eV. As-deposited CuSbS2 films are p-type and a hetero-junction in the nZnO–pCuSbS2 structure showed rectifying current–voltage behavior and low reverse current consistent with compact pinhole free CuSbS2 film synthesized by ionic liquid electrodeposition.