Optimisation of thermal annealing parameters for different thickness of active layers based on polymer/fullerene bulk heterojunction solar cells.

Thin film polymer solar cells have been fabricated using regioregular poly(3-hexylthiophene) (P3HT) within [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) bulk heterojunction active layer. The influence of the thermal annealing temperature and the time duration on the performance of P3HT/PCBM bulk heterojunction solar cells based on different thickness of active layers has been investigated. The results demonstrate that thermal annealing is a thermally activated kinetic process. The effect is almost the same for high temperature annealing for a short time and low temperature annealing for a long time at a temperature greater than the glass temperature of P3HT. The device with a thicker active layer requires a higher temperature or a longer time annealing treatment to achieve the optimised phase separation for efficient charge separation and transport and thereby leads to optimal performance. The device with a thinner active layer requires a lower temperature or a shorter time annealing treatment to achieve the optimal performance. [ABSTRACT FROM AUTHOR]