ZnO–silicon heterojunction solar cell having high efficiency and high fill factor is structured and simulated to study its photovoltaic properties under different device temperature. Current–voltage measurement of dimensionally optimised device structure revealed up to 20.44% efficiency and 83.66% fill factor at 1 Ω-cm² external series resistance at 300 K. Measured current–voltage shows decrease of open-circuit voltage from 659.13 to 109.1 mV and short-circuit current from 40.65 to 39.5 mA/cm² with increase of device temperature. Quasi-steady-state photoconductance measurement reveals small recombination current and long Shockley Read Hall lifetime under the selected temperature range indicating superior performance of the device. Adverse effect of surface recombination velocity at rear surface of the device is observed at lower temperature (100–600 K) range indicating better majority carrier collection at very high temperature 700 K and above.