Effects of morphology evolution on solution-processed small molecule photovoltaics via a solvent additiveElectronic supplementary information (ESI) available: Experimental section, additional figures and tables as mentioned in the main text. See DOI: 10.1039/c7tc02088k

• Main Authors: Hoang, Quoc Viet, Rasool, Shafket, Oh, Sora, Van Vu, Doan, Kim, Da Hun, Lee, Hang Ken, Song, Chang Eun, Lee, Sang Kyu, Lee, Jong-Cheol, Moon, Sang-Jin, Shin, Won Suk
• Format: Journal Article
• Language: English
• Published: 10.08.2017
• ISSN: 2050-7526; 2050-7534
• DOI: 10.1039/c7tc02088k

A newly synthesized small molecule donor, BDTT-2DPPBFu , is designed for incorporation into the photo-active layer in solution-processed small molecule organic photovoltaics (SM-OPVs). The effects of a solvent additive (1-chloronaphthalene, CN) on the bulk heterojunction morphology of a BDTT-2DPPBFu donor:fullerene derivative acceptor (PC 71 BM) are investigated and correlated with the device performance. A TEM analysis revealed that the nanomorphology of the SM-OPVs evolved dramatically with increasing solvent additive volume. With an optimum concentration of 2.5 vol% CN, a nanomorphology with a fibrillar and interpenetrating network on the order of exciton diffusion length (∼10-15 nm) is formed, resulting in improvement of the short-circuit current density, fill factor, and power conversion efficiency. Further GIWAXS studies have shown that the π-π stacking distance of BDTT-2DPPBFu small molecules is reduced and the inter-mixing of PC 71 BM within the BDTT-2DPPBFu -rich phase in the photo-active layer processed from 2.5 vol% CN is increased, leading to enhanced charge transport and reduced charge recombination and transfer resistance. The present work provides important progress in the nanomorphology of the photo-active layer, which can be effectively tuned via the use of a solvent additive in SM-OPVs. A newly synthesized small molecule donor, BDTT-2DPPBFu , is designed for incorporation into the photo-active layer in solution-processed small molecule organic photovoltaics (SM-OPVs).