Atomic layer deposited ZnO:B as transparent conductive oxide for increased short circuit current density in silicon heterojunction solar cells

摘要

A key factor to improve the performance of silicon heterojunction solar cells (SHJ) is increasing their short circuit density (J_(sc)) by reducing the parasitic absorption of light in the front side of the cell. Therefore, we have investigated the replacement of the conventional sputtered ITO on the SHJ front side with highly transparent boron doped zinc oxide (ZnO:B). The ZnO:B is prepared by atomic layer deposition (ALD) with the novel triisopropyl borate precursor, B(0'Pr)3 (TIB), which presents an easy controllable and safer alternative to commonly used boron precursors. Outstanding J_(sc) values of 35.50 mA/cm~2 for cells on double sided polished wafer (DSP) and 38.76 mA/cm~2 for cells on textured wafer are observed for SHJ cells with ZnO:B, as compared to 33.48 mA/cm~2 (DSP) and 37.31 mA/cm~2 (textured) for reference cells with ITO. The potential of ZnO:B grown with TIB as indium-free TCO with increased transmission for SHJ solar cells is thereby demonstrated. Furthermore, indium free SHJ solar cells with ALD deposited ZnO:B as front TCO and ZnO:Al as back TCO have been successfully demonstrated.