In this study, the impacts of temperature on the light current-voltage characteristics of heterojunction solar cells fabricated on gallium-doped crystalline p-type silicon (c-Si) has been studied under air mass zero spectrum (136.7 mW/сm²) in the temperature range from 173 to 373 K. Our experimental results indicated that the short-circuit current density increased linearly with temperature, exhibiting a positive temperature coefficient of 0.058%/K, whereas the open-circuit voltage (Vос) decreased linearly. From the experiment, the calculated temperature coefficient value of the Vос was found to be −0.182%/K. Both the maximum output power and conversion efficiency of the heterojunction solar cells increased linearly with decreasing temperature from 373 K, reaching peak values of ~29.5 mW/cm² and ~21.5% at 173 K. The temperature coefficient of the maximum output power was evaluated to be −0.2%/K, which represents one of the record-breaking small values reported among SCs based on other single c-Si technologies.