Equiaxed–columnar stacked TCO films for efficient silicon heterojunction solar cells

Zr, Ti and Ga-doped indium oxide (ITGZO) films with different structures were prepared by radio frequency (RF) magnetron sputtering method. The equiaxed–columnar stacked films which possess excellent carrier transport efficiency were designed, and their microstructure, electrical, optical and energy band properties were investigated systematically in this paper. The application of the stacked films has comprehensively improved the parameters of silicon heterojunction (SHJ) solar cells including series resistance (R_s), short-circuit current (I_sc), fill factor (FF), and the final device efficiency (η). The gain in device performance mainly comes from three aspects: better crystalline quality, less grain boundary scattering, and the appropriate work function (W_F). Furthermore, an interface modification layer with high carrier concentration was also used to improve the ITGZO/a-Si:H (hydrogenated amorphous silicon) interface carrier transport property. Benefit from this modification layer, the FF of SHJ solar cells increased from 77.71 to 81.51% and the I_sc increased from 9.359 to 9.465 A. This work provides a feasible guidance for the structural design of transparent conductive oxide layer in SHJ solar cell.