High-performance Ti and W co-doped indium oxide films for silicon heterojunction solar cells prepared by reactive plasma deposition

Abstract

Titanium and tungsten co-doped indium oxide (IWTO) films are deposited via low-damage reactive plasma deposition technique at room temperature (RT) and heating temperature (HT). The effects of oxygen flow rates (FO2) on the structural, optical and electrical properties of the IWTO films are investigated after air annealing. X-ray diffraction and scanning electron microscopy results show that the IWTO films are polycrystalline structure exhibiting a preferred (222) crystal plane orientation. As FO2 increases from 10 sccm to 80 sccm, carrier concentration decreases by an order of magnitude for both RT and HT condition, while carrier mobility first increases and then decreases. It is noteworthy that films fabricated at HT show highest mobility (92.1 cm2 V−1 s−1) and lowest resistivity (2.13 × 10−4 Ω cm) due to better crystallinity and hence decreased grain boundary scattering. In addition, the average transmittance of the IWTO films exceeds 89.5% in the wavelength range of 400–1200 nm. Finally, silicon heterojunction solar cells with a high efficiency of 23.8% (with open-circuit voltage (Voc) of 0.746 V, short-circuit current density (Jsc) of 38.7 mA cm−2 and fill factor (FF) of 82.9%) is achieved with the application of the high-performance IWTO film.