Bulk heterojunction solar cells based on self-assembling disc-shaped liquid crystalline material

Abstract

In this article, effect of addition of disc-shaped liquid crystalline material, namely 2, 3, 6, 7, 10, 11-hexabutyloxytriphenylene, in poly (3-hexylthiophene): [6, 6]-phenyl-C61-butyric acid methyl ester containing bulk heterojunction (BHJ) solar cells has been investigated. These disc-shaped molecules organise into ordered columnar hexagonal structures through intermolecular π − π interactions as monitored by polarised light optical microscopy. Current–voltage characteristics of the device prepared with liquid crystal layer exhibited a short-circuit current of 10.5 mA cm−2 and a fill factor of 35%. The resultant power conversion efficiency (PCE) was 1.54%. The influence of varying the thickness of liquid crystal layer and annealing on these solar cells was also studied. The short circuit current and PCE of 12.9 mA cm−2 and 2.3% was achieved for these BHJ solar cells containing self-organised discotic liquid crystals in the active layer under one sun condition after annealing.