Conformation Flipping of Asymmetric Nonfullerene Acceptors Enabling High‐Performance Organic Solar Cells with 77% Fill Factors

Abstract

The innovation of photovoltaic materials, [1][2][3][4][5] specially nonfullerene acceptors (NFAs), has pioneered many research hot spots of organic solar cells (OSCs) for in-depth exploration in the past decades. With combinational efforts devoted to molecule evolution and device engineering, the power conversion efficiency (PCE) of single-junction solar cells has approached up to 19%. [6][7][8] Various NFAs have been developed in recent years, such as diketopyrrolopyrrole (DPP) or perylene diimide (PDI) contained molecules, [9][10][11] A-D-A-type acceptors, i.e., ITIC, [12,13] M series [14] and Y series molecules, [15][16][17][18] typically Y6. [19] Core engineering has been demonstrated effective to achieve highperformance NFAs, as molecular conjugation and intramolecular charge transfer (ICT) can be readily realized through introducing or removing the aromatic rings on the backbone of NFAs. Additionally, the asymmetric strategy was adopted for molecule modification, which could precisely regulate the intrinsic optoelectronic properties of NFAs. Derived from symmetric NFAs, i.e., ITIC [12] and IT-4F, [20] various A-D-A-type asymmetric NFAs have been designed and synthesized. [21,22] Sun's group designed asymmetric TPTT-2F and TPTTT-2F through extending molecular conjugation of the IDT core. [23] Along with the enhanced conjugation, redshifted

A‐D‐A Type Nonfullerene Acceptors Synthesized by Core Segmentation and Isomerization for Realizing Organic Solar Cells with Low Nonradiative Energy Loss

“…[ 33,34 ] As plotted in Figure 3d and Figure S10 (Supporting Information), the HOMO energy levels of TPBTT‐4F and TPBTT‐4Cl were measured to be −5.63 and −5.64 eV. The LUMO energy levels were calculated to be −5.19 and −5.24 eV, in combination with E opt g. According to the energy levels of PTBTT‐4F/4Cl reported recently, [ 19 ] TPBTT derivatives achieved elevated HOMO energy levels and maintained LUMO energy levels. Inferred from the compressed E opt g and similar LUMO energy levels, the isomerization prepared TPBTT derivatives would obtain suppressed E Loss .…”

“…[ 18 ] The asymmetric PTBTT‐4F/4Cl exhibited sufficient driving force for exciton dissociation, leading to higher J SC and FF). [ 19 ]…”

Asymmetric Non-Fullerene Acceptor Derivatives Incorporated Ternary Organic Solar Cells

“…In our previous work, we designed and synthesized two A–D–A type ITIC derivatives with different central cores, named PTBTT-4F and PTBTP-4F. , The symmetric molecule PTBTP-4F was constructed with a central core based on a thiophene­[3,2- b ]­pyrrole (TP) block serving as the D core (fusing two pyrrole rings on both sides of an indaceno­dithiophene (IDT) unit) together with two accepting units (IC-2F), while the central core of asymmetric PTBTT-4F was built with a TP block and thiophene­[3,2- b ]­thiophene (TT) units. Here, both PTBTT-4F and PTBTP-4F were introduced into the PM6:BTP-BO-4F (Y6-BO) binary host to fabricate ternary devices.…”

C-Shape or S-Shape? The Molecular Geometry Control of Fused-Ring Nonfullerene Acceptors for Lower Energy Loss in Organic Solar Cells

“…Organic solar cells (OSCs) have garnered significant attention for their advantageous features, such as flexibility, light weight, and suitability for large-area manufacturing. − Recently, owing to the innovation of fused-ring nonfullerene acceptors (FRNFAs), particularly the state-of-the-art Y-series acceptors, the power conversion efficiency (PCE) of OSCs has experienced a noteworthy breakthrough, resulting in an impressive PCE surpassing 19%. − To date, significant endeavors have been dedicated to investigate the association between the structure–property–performance relationship of NFAs through the molecular modifications on the central fused-ring units, − side chains, ,− and terminal groups. − Among them, the impact of isomeric molecular geometry on device performance has been less reported. − Of note, to achieve further PCE improvement of OSCs, it is crucial not only to focus on molecular optimization of FRNFAs but also to elucidate the underlying structural mechanisms responsible for the outstanding performance, which will serve as a guide for future molecular design.…”