Innovative Wide-Spectrum Mg and Ga-Codoped ZnO Transparent Conductive Films Grown via Reactive Plasma Deposition for Si Heterojunction Solar Cells

Abstract

In this work, wide-spectrum Mg and Ga-codoped ZnO (MGZO) transparent conductive films are developed via a reactive plasma deposition (RPD) technique with a soft thin-film growth process. MGZO film with a work function of ∼4.36 eV can be achieved within 12 min without any intentional substrate-heating treatment. The 480 nm-thickness MGZO film exhibits a low resistivity of ∼9.9 × 10–4 Ω cm and a high transmittance of ∼82.6% in the UV–vis–NIR region (λ approximately 400 nm–1200 nm). XRD spectra show that MGZO films exhibit (103) preferred orientation as the film thickness increases. A silicon heterojunction (SHJ) solar cell based on 480 nm-thick MGZO at the front side is completed. Excellent continuity of the MGZO film is proven by the cross-sectional SEM images, and there are no cracks and pinholes on the top or bottom of the c-Si pyramids. Further efficiency improvements are achieved using an ultrathin SnOx buffer layer with an ameliorated p-a-Si:H/TCO interface. Also, a silicon heterojunction (SHJ) solar cell using MGZO films on both sides is achieved with a conversion efficiency of 19.02%. These experimental results demonstrate that low-cost RPD-grown MGZO TCO materials could be commercially appropriate replacements for the conventional In2O3-based materials commonly used in SHJ solar cells and other optoelectronic devices.