Optimization of p-Type Hydrogenated Microcrystalline Silicon Oxide Window Layer for High-Efficiency Crystalline Silicon Heterojunction Solar Cells

Abstract

Wide-gap, high-conductivity p-type hydrogenated microcrystalline silicon oxide (p-µc-SiO:H) films deposited by very high frequency plasma-enhanced chemical vapor deposition (60 MHz VHF-PECVD) at a low substrate temperature of approximately [200 °C] were used as window layers in n-type crystalline silicon (n-c-Si) heterojunction (HJ) solar cells. We investigated the effect of p-µc-SiO:H window layer thickness on HJ solar cells by changing deposition time and silane (SiH4) flow rate. The effects of carbon dioxide flow rate on the p-µc-SiO:H window and i-a-SiO:H buffer layer were also studied. Employing a p-µc-SiO:H/i-a-SiO:H/n-c-Si [Czochralski (CZ), 200 µm, (100)]/i-a-Si:H/n-a-Si:H configuration, we achieved an efficiency of 17.8% (active area efficiency) with an open-circuit voltage (Voc) of 665 mV. The solar cells showed a spectral response of about 0.83 at a wavelength of 400 nm, which is higher than that of conventional HJ solar cells with amorphous silicon window layers.