Efficiency enhancement in small molecule bulk heterojunction organic solar cells via additive

Improved performance of small molecule bulk heterojunction (BHJ) organic solar cells based on 4,7-bis(2-triphenylamino-3-dodecyl-thiophene-5-yl)-benzo[c][1,2,5]thiadiazole (TTBTT)/PC71BM (1:3, w/w) blend has been obtained by using 1,8-octanedithiol (ODT) as a processing additive. Based on the analysis of absorption spectrum, charge transport, and film morphology, the 30% enhancement in power conversion efficiency (PCE) via 1% ODT addition is attributed to aggregated domain formation, enhanced absorption, improved hole mobility, and more balanced charge transport. Finally, a PCE as high as 2.86% was achieved, which is among the top reported for solution-processed small molecule BHJ organic solar cells.

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