Textured transparent conductive B/Al doped ZnO films utilizing reactive magnetron sputtering

Abstract

High-quality textured transparent conductive oxide (TCO) is significant to the exceptional performance of solar cells. In this study, textured B/Al doped ZnO (ZnO:B/Al) films were first reported utilizing reactive RF magnetron sputtering from an intrinsic ZnO ceramic target in a B₂H₆–Ar gas mixture. Elaborate thermal treatment was conducted for film optimization, as the temperature dependency of the B₂H₆ source was quite sensitive. A compound structure with a 200 nm thick Al capping layer and 2000 nm thick ZnO:B main layer was proposed to further improve the annealing performance. The initial resistivity and mobility of the reactive sputtered ZnO:B/Al film were 4.8 × 10⁻⁴ Ω cm and 32.1 cm² V⁻¹ s⁻¹ respectively. A remarkable surface texture with root-mean-square higher than 170 nm developed after a chemical etching procedure, resulting in average light scattering over 89% and total transmittance higher than 86% in the whole spectrum. These optical properties illustrate prominent progress in TCO application in thin film silicon (TFS) solar cells. Preliminary microcrystalline silicon solar cells deposited on textured ZnO:B/Al films indicate 0.6 mA cm⁻² enhancement in short-circuit current density compared to conventional ZnO:Al front contacts, indicating potential application in high-efficiency TFS solar cells.