Comparison of ITO, In2O3:Zn and In2O3:H transparent conductive oxides as front electrodes for silicon heterojunction solar cell applications

In this study, we presented a comparative investigation on the electrical, optical, and structural properties of three types of transparent conductive oxides (TCOs), including tin-doped indium oxide (ITO), zinc-doped indium oxide (IZO) and hydrogen-doped indium oxide (In2O3:H or IO:H) films. Post-annealing treatment (195 °C, 30 min, and air ambient) was performed to optimize the material characteristics of the TCOs. Further, we evaluated the applications of ITO, IZO and IO:H films in silicon heterojunction (SHJ) solar cells. The effects of material characteristics of TCOs on the device performance were studied. It was found that the ITO films with a low resistivity contributed to the fill factor of the SHJ solar cells, while the IZO films showed obvious advantage in open-circuit voltage of the cells, with the best value of 0.736 V. Comparing with ITO and IZO films, the resulting IO:H films feature both highest carrier mobility (with the best value of 100 cm2/V·s) and band gap values after annealing, which contribute to the short-circuit current density of 39.18 mA/cm2. The SHJ solar cell with IO:H films as front TCO layer, showed a large scale (153.4 cm2) power conversion efficiency of 21.13%, showing an obvious enhancement compared to the ITO and IZO counterparts.