| Summary: | Organic photovoltaic (OPV) with power conversion efficiency (PCE) of 7% has been demonstrated in literature and has since attracted a lot of interest within the scientific community. One of the best OPVs are based on bulk heterojunctions (BHJ) of poly(3-hexylthiophene): [6,6]-phenyl C61-butyric acid methyl ester (P3HT:PCBM). However, to achieve this PCE, heat treatment was needed to improve the π-π stacking of P3HT. Thus, thermal-free method is preferable to obtain higher PCE. Approaches such as incorporation of additive and preassembling P3HT into nanofiber have been adopted as thermal-free methods in modifying blend morphology. In this project, we studied the effect of addition of regio-random P3HT (rra-P3HT) and monomer 3HT in the growth of P3HT-nanofiber following its applications in OPV devices based on its blend with PCBM (P3HT-nf:PCBM).
For the system with rra-P3HT additions, UV-vis and AFM characterization techniques confirmed the ordered structures of P3HT. However, the rra-P3HT based devices did not show improvement in PCE. This could be due to the reduction in photocurrent which caused by the decrease in hole mobility. However, 3HT-based devices showed an enhancement in photocurrent but a lower open-circuit voltage. However, the overall PCE improved to around 2.6% by adding ratio of 3:10 P3HT:3HT. The enhancement in short-circuit current was due to the increase in crystallinity of P3HT.
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