Thin film solar cell based on p-CuSbS2 together with Cd-free GaN/InGaN bilayer

CuSbS 2 thin film solar cell with 2.99 % efficiency has been demonstrated by using the Cd-free GaN and In 0.15 Ga 0.85 N as n -type semiconductor bilayer. CuSbS 2 films on the TiN-coated Mo/glass substrates were made by co-sputtering technique at 300 °C with a cermet target of (Cu + Sb 2 S 3 ) operated at 50–60 W and a metal target of Cu at 2 W, followed by thermal annealing at 350–450 °C for 1 h. The effects of processing conditions on the growth behavior, microstructural characteristics, and electrical properties of CuSbS 2 films had been investigated. Solar cell devices were fabricated by depositing ~50 nm GaN and ~300 nm In 0.15 Ga 0.85 N layers with low temperature radio-frequency (RF) sputtering method, followed by RF sputtering 300–400 nm indium-tin oxide for front contact and pasting silver glue for electric contacts. The CuSbS 2 thin film sputtered at 55 W had a [Cu]/[Sb] ratio of 0.80 with co-exists of the Sb 2 S 3 , and had a hole concentration of 1.41 × 10 18 cm −3 , an electrical conductivity 0.1 S cm −1 , and mobility of 13 cm 2 V −1 s −1 . The efficiency of the solar cell device had a 3.83-fold increase if the p -CuSbS 2 /CdS/ n -ZnO system had its conventionally designed CdS/ n -type ZnO layer replaced by n -type GaN/In 0.15 Ga 0.85 N bilayer.