Abstract
Liquid crystalline materials are available as a self-organizing molecular semiconductor, and are possibly applied to introduce a molecularly ordered structure for bulk hetero junction (BHJ) solar cells because of easy control of molecular orientation and self-organization. In this study, we investigated the effect of molecular orientation on solar cell performance with a smectic liquid crystal of pyrrolopyrrole derivative for the first step of molecularly ordered BHJ solar cells. We found that the thermal annealing of the cell induced re-orientation of the molecular orientation from perpendicular to parallel, and the power conversion efficiency was improved by one order of magnitude from 0.05% to 0.78% under AM-1.5 illumination.
