Silicon heterojunction solar cells with electron selective TiOx contact

• High quality electron selective TiOx contact for silicon solar cells.
• Excellent silicon surface passivation (iVoc700mV) is achieved with thin TiOx film.
• Moderate contact resistivity (~0.25 Ω cm2) is obtained on the TiOx/Si heterojunction.
• A simple silicon heterojunction solar cell with the champion efficiency of 20.5%.

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 TiOx films deposited by atomic layer deposition on silicon are investigated via simultaneous consideration of the surface passivation quality and the contact resistivity. Thin TiOx films are demonstrated to provide not only good passivation to silicon surfaces, but also allow a relative low contact resistivity at the TiOx/Si heterojunction. A maximum implied open-circuit voltage (iVoc) of ~703 mV is achieved with the passivation of a 4.5 nm TiOx film, and a relatively low contact resistivity of (~0.25 Ω cm2 is obtained at the TiOx/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 TiOx contacts. A simulated efficiency of up to 23.7% is achieved on the n-type solar cell with a full-area TiOx contact. The efficient, low cost electron-transporting/hole-blocking TiOx layer enables the fabrication of high efficiency silicon solar cells with a simplified process flow.

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