Thermal annealing induced bicontinuous networks in bulk heterojunction solar cells and bipolar field-effect transistors

Abstract

Polymer bulk heterojunction solar cells fabricated from poly(2,5-bis(3′-dodecyl-2,2′-bithiophen-5-yl)-3,6-dimethylthieno [3,2-b] thiophene):[6,6]-phenyl-C61-butric acid methyl ester (1:1, w/w) blend showed significantly improved power conversion efficiency (PCE), from 0.96% to 2.32%, with post-thermal annealing at 140 °C. Charge transport properties obtained from bipolar field-effect transistors indicated that post-thermal annealing induced the assembly of significantly improved bicontinuous networks and excellently balanced hole (7.2×10−3 cm2 V−1 s−1) and electron (5.8×10−3 cm2 V−1 s−1) mobilities (due, particularly, to improved electron mobility), thereby improving PCE.