Hydrogen‐Bonding Strategy to Optimize Charge Distribution of PC₇₁BM and Enable a High Efficiency of 12.45% for Organic Solar Cells

Abstract

Short‐circuit current density (JSC), fill factor (FF), and open‐circuit voltage (VOC) are the determining factors on organic solar cells (OSCs) performance. For ternary blend devices, the VOC generally shows a smaller change compared to their binary blend counterpart. Therefore, increase in the JSC and FF of ternary OSCs is the dominating approach to improve device performance. Here, we report a new strategy to enhance OSCs performance via hydrogen‐bonding between PC71BM and dopant coumarin7 (C7) in a PTB7‐Th:C7:PC71BM ternary system. The formation of hydrogen bonds between PC71BM and C7 was predicted by Vienna ab initio simulations (VASP) and verified by Fourier‐transform infrared spectroscopy (FT‐IR). Hydrogen‐bonding induces charge accumulation on the surface of PC71BM, which facilitates electron withdrawal of PC71BM and π‐π stacking between donor and acceptor, resulting in enhanced JSC values of OSCs. Besides, hydrogen bond interaction improves the morphology of C7‐containing OSCs via formation of an interpenetrating network nanofiber structure, as revealed by transmission electron microscopy (TEM). The combination of the above benefits yields a ternary blend OSC consisting of PTB7‐Th:10%C7:PC71BM to have an average power conversion efficiency (PCE) of 12.23% (maximum PCE of 12.45%) at a JSC of 22.26 mA cm−2 and a FF of 70.71%, which represents 31.89% enhancement above the best PCE of the control OSC (9.44%). These results demonstrate a new strategy to improve OSCs efficiency.

Efficient ternary organic photovoltaics with two polymer donors by minimizing energy loss

“…The charge recombination can be evaluated according to the J SC dependence on I obeying the power law equation J SC f I s , where s is the exponential factor and the slope of the tted line. [43][44][45] The tted 's' values are 0.92 and 0.94 for PF2:Y6 based and optimized ternary OPVs, respectively. The tted 's' value for the optimized ternary OPVs is closer to 1, indicating that the bimolecular recombination in active layers can be slightly restrained with appropriate J71 incorporation.…”

Organic Amines as Targeting Stabilizer at the Polymer/Fullerene Interface for Polymer:PC61BM Solar Cells

“…Interestingly, coumarin derivatives were also found to be able to improve the performance and stability of PSCs, both in fullerene and nonfullerene solar cell systems, which was attributed to the formation of intermolecular hydrogen bonding between coumarin and PC 71 BM or ITIC through NH…OC bonds. [ 11 ] In addition, H…π bond between polarized NH groups and electron‐rich π‐conjugation systems (e.g., C 60 ) is a kind of hydrogen bond that exists in many molecule systems. [ 12 ] It can be expected that organic amines which contain NH bond should be able to complex with PC 61 BM through intermolecular hydrogen bonds.…”

Introducing Trifluoromethyl to Strengthen Hydrogen Bond for High Efficiency Organic Solar Cells

“…In this work, we designed and synthesized a novel small molecule with a simple structure, DTBO (7-(dibutylamino)-3-(6-(trifluoromethyl)-1H-benzo[d]imidazol-2-yl)-2H-chromen-2-one), via introducing trifluoromethyl on a previously reported small molecule Coumarin 7 (3-(1H-benzo[d]imidazol-2-yl)-7-(diethylamino)-2H-chromen-2-one) (Du et al, 2018). Due to the poor performance in ternary non-fullerene OSCs, we introduce trifluoromethyl on Coumarin 7 to strengthen the hydrogen bond with the non-fullerene acceptor in order to obtain a great impact on the acceptor.…”