Open AccessDithieno[3,2‐ b :2ʹ,3ʹ‐ d ]pyrrol‐Fused Asymmetrical Electron Acceptors: A Study into the Effects of Nitrogen‐Functionalization on Reducing Nonradiative Recombination Loss and Dipole Moment on Morphology
Author(s) -
Gao Wei,
Liu Tao,
Sun Rui,
Zhang Guangye,
Xiao Yiqun,
Ma Ruijie,
Zhong Cheng,
Lu Xinhui,
Min Jie,
Yan He,
Yang Chuluo
Publication year - 2020
Publication title -
advanced science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 5.388
H-Index - 100
ISSN - 2198-3844
DOI - 10.1002/advs.201902657
Subject(s) - dipole , surface modification , organic solar cell , materials science , molecule , conjugated system , recombination , moment (physics) , electron , capacity loss , chemistry , organic chemistry , physics , polymer , biochemistry , classical mechanics , quantum mechanics , gene , electrode , electrolyte
Abstract Energy loss ( E loss ) consisting of radiative recombination loss (Δ E 1 and Δ E 2 ) and nonradiative recombination loss (Δ E 3 ) is considered as an important factor for organic solar cells (OSCs). Herein, two N ‐functionalized asymmetrical small molecule acceptors (SMAs), namely N7IT and N8IT are designed and synthesized, to explore the effect of N on reducing E loss with sulfur (S) as a comparison. N7IT‐based OSCs achieve not only a higher PCE (13.8%), but also a much lower E loss (0.57 eV) than those of the analogue (a‐IT)‐based OSCs (PCE of 11.5% and E loss of 0.72 eV), which are mainly attributed to N7IT's significantly enhanced charge carrier density (promoting J SC ) and largely suppressed nonradiative E loss by over 0.1 eV (enhancing V OC ). In comparison, N8IT, with an extended π‐conjugated length, shows relatively lower photovoltaic performance than N7IT (but higher than a‐IT) due to the less favorable morphology caused by the excessively large dipole moment of the asymmetrical molecule. Finally, this work sheds light on the structure–property relationship of the N ‐functionalization, particularly on its effects on reducing the E loss , which could inspire the community to design and synthesize more N ‐functionalized SMAs.