We present the investigations carried out on the effect of temperature on the performance of hydrogen phthalocyanine (H₂Pc)/fullerene (C₆₀) bilayer organic photovoltaic (OPV) devices. Prior to these investigations the thicknesses of the active layers were optimised to get the best performance. The optimised device had an efficiency of ~0.5% at 307 ^oK. The investigations on the best device showed that temperature has significant effect on the photovoltaic performance. Short circuit current density (J_sc) and fill factor (FF) decrease while open circuit voltage (V_oc) increases with reduction in temperature. In overall the efficiency first increases and then decreases with reduction in temperature. The reduction in J_sc and FF is because of the temperature dependent electronic properties of the organic materials. We have developed a model which shows that the built in voltage (V_bi) of the devices increases with reduction in temperature. The increment in V_oc with reduction in temperature has been attributed to the increment in V_bi.

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