Effects of stirring temperature of P3HT:PCBM solution on device performance of organic photovoltaics

In organic photovoltaics (OPVs), bulk heterojunction (BHJ) is an efficient strategy to enhance their power conversion efficiency (PCE) by increasing the interface area between donor and acceptor materials. For the formation of favorable donor–acceptor networks, various conditions in fabricating a BHJ film should be optimized. In this study, the effects of the stirring temperature of a poly(3-hexylthiophene-2,5-diyl) (P3HT):[6,6]-phenyl-C 61 -butyric acid methyl ester (PCBM) solution on the OPV performance were investigated. High uniformity was attained in the BHJ film fabricated using a solution stirred at 80 °C. However, in the BHJ film fabricated using a solution stirred at room temperature (RT), large PCBM aggregates were formed. Such PCBM aggregates deteriorated both the ordering of P3HT chains and the networks of P3HT and PCBM. Consequently, the PCE of the OPV was considerably decreased with the use of a P3HT:PCBM solution stirred at RT. Thus, sufficiently high stirring temperatures in preparing a P3HT:PCBM solution are essential to achieving efficient BHJ OPVs.