Impact of symmetry-breaking of non-fullerene acceptors for efficient and stable organic solar cells

Abstract

The concurrent enhancement of the short-circuit current (JSC) and open-circuit voltage (VOC) is a key problem in the preparation of efficient organic solar cells (OSCs). In this paper, we report...

Single‐Junction Organic Solar Cells with 19.17% Efficiency Enabled by Introducing One Asymmetric Guest Acceptor

“…The results indicate that only one crystallization pattern is formed in the L8-BO:BTP-2F2Cl blend, confirming the formation of the alloylike phase. [32,34] Additionally, we have measured the PLQY of the corresponding acceptors (Figure S8, Supporting Information). The PLQY values of L8-BO, BTP-2F2Cl and L8-BO:BTP-2F2Cl are 3.2%, 5.5% and 3.8%, respectively.…”

“…More recently, Sun and co-workers developed an NFA named L8-BO by substituting the beta position of the thiophene unit on the Y6-central core with branched alkyl chains, [5] which exhibits upshifted energy levels and improved molecular packing, thus yielding a PCE of 18.32% with a FF of 81.5% in PM6:L8-BO OSCs. Apart from the terminal group and side-chain engineering, the asymmetric designs (in endgroups, [34,35] side-chains, [36] skeleton, [37][38][39] etc.) enable the photovoltaic systems to get further a step in device performance owing to the fine-tuning of photophysical and electrochemical properties, molecular orientation and stacking pattern, etc.…”

Recent Progress of Y6‐Derived Asymmetric Fused Ring Electron Acceptors

“…These results demonstrated that asymmetric structural modifications of NFAs were a valuable strategy for simultaneously promoting the photovoltaic performance and stability of OSCs. [69] In 2022, Chen et al developed an asymmetric FREA with the halogenated-thiophene-fused end group (CPTCN-Cl) and the halogenated-benzene-fused one (IC-2Cl), namely AC9, to fabricate the highly efficient OSCs. [82] The resulting PM6:AC9based binary OSC reached a record PCE of 18.43% (18.1% certified), with a V OC of 0.871 V, a J SC of 26.75 mA cm -2 , and an FF of 79.00%, higher than that (18.11%) of symmetrical classical acceptor BTP-eC9, [83] being ascribed to the sufficient charge transfer and reduced carrier recombination by a suitable concession between charge generation and non-radiative charge recombination.…”

Watching Excited-State Symmetry Breaking in Multibranched Push–Pull Molecules

“…Over the past few years, symmetric molecules containing two or more electron donor–acceptor (D–A) branches have been attracting considerable attention. These molecules are being increasingly used as two-photon absorbers, electron acceptors, or new luminescent materials in applications as diverse as fluorescence microscopy, , photopolymerization, , organic photovoltaics, , or organic light-emitting diodes. , Although these compounds do not possess a permanent electric dipole moment, their fluorescence usually exhibits a strong solvatochromism that is, in some cases, as large as that measured with the single-branched D–A analogue. − This behavior was explained in terms of excited-state symmetry breaking (ES-SB), i.e., a transition from a symmetric and multipolar state to an asymmetric and dipolar state. , In principle, emission solvatochromism cannot be considered as an unambiguous evidence of ES-SB, unless it is as large as that of the single-branch analogue. Indeed, quadrupole–dipole and octupole–dipole interactions do also contribute to the solvation energy and, hence, give rise to a solvatochromism.…”

“…O ver the past few years, symmetric molecules containing two or more electron donor−acceptor (D−A) branches have been attracting considerable attention. These molecules are being increasingly used as two-photon absorbers, electron acceptors, or new luminescent materials in applications as diverse as fluorescence microscopy, 1,2 photopolymerization, 3,4 organic photovoltaics, 5,6 or organic light-emitting diodes. 7,8 Although these compounds do not possess a permanent electric dipole moment, their fluorescence usually exhibits a strong solvatochromism that is, in some cases, as large as that measured with the single-branched D−A analogue.…”