Figure 1
a A schematic representation of the P3HT/PCBM blend materials on the quartz substrate. The zoom shows the morphology of this bulk heterojunctions and thearrow indicates the molecular structure of the PCBM.b Energy band diagram of blend materials for bound and mobile electrons and holes. Thearrows P1and P2represent the localized polarons whereas the DP1and DP2represent the delocalized polarons, respectively. PA3represents the secondary excitation of free electrons in the PCBM and SE the stimulated emission