Investigation of electrical characteristics of P3HT:PCBM organic solar cells

Capacitance of P3HT(poly (3-hexylthiophene-2,5-diyl)):PCBM ([6,6]-phenyl C61-butyric acid methyl ester) bulk heterojunction solar cell was measured at different biases and different temperatures (25°C and 130°C). The capacitance was found to vary with bias voltages, and showed different trends with temperature, but the peak capacitance values and positions did not vary much. Mott-Schottky relation was used to model the behavior of capacitance in reverse bias. The capacitance of pure P3HT showed a different trend as compare to the P3HT:PCBM blend. The peak position did not vary, but the peak values decrease with temperature. Permittivity of P3HT was then calculated and the temperature dependence of exciton binding energy was revealed. The active layer thickness effect on the series resistance was also examined. The results show two regions, the slope quickly changes after certain thickness. Further investigation of electrical prosperities will provide insight on the origin of open circuit voltage and charge transport mechanism.