Silicon heterojunction solar cells with electron selective TiO_x contact

Silicon solar cells featuring carrier selective contacts have been demonstrated to reach ultra-high conversion efficiency. In this work, the electron-selective contact characteristics of ultrathin TiO_x films deposited by atomic layer deposition on silicon are investigated via simultaneous consideration of the surface passivation quality and the contact resistivity. Thin TiO_x films are demonstrated to provide not only good passivation to silicon surfaces, but also allow a relative low contact resistivity at the TiO_x/Si heterojunction. A maximum implied open-circuit voltage (iV_oc) of ~703 mV is achieved with the passivation of a 4.5 nm TiO_x film, and a relatively low contact resistivity of (~0.25 Ω cm² is obtained at the TiO_x/n-Si heterojunction simultaneously. N-type silicon solar cell with the champion efficiency of 20.5% is achieved by the implementation of a full-area electron-selective TiO_x contacts. A simulated efficiency of up to 23.7% is achieved on the n-type solar cell with a full-area TiO_x contact. The efficient, low cost electron-transporting/hole-blocking TiO_x layer enables the fabrication of high efficiency silicon solar cells with a simplified process flow.