PBDB-T-Based Binary-OSCs Achieving over 15.83% Efficiency via End-Group Functionalization and Alkyl-Chain Engineering of Quinoxaline-Containing Non-Fullerene Acceptors

Abstract

Molecular backbone modification, alkyl-chain engineering, and end-group functionalization are promising strategies for developing efficient high-performance non-fullerene acceptors (NFAs). Herein, two new NFAs, named TPQ-eC7-4F and TPQ-eC7-4Cl, are designed and synthesized. Both molecules have linear octyl chains on fused quinoxaline-containing heterocyclics as the central backbone and difluorinated (2F)/dichlorinated (2Cl) 1,1-dicyanomethylene-3-indanone (IC) as the end-group units. The influences of alkyl-chains on fused quinoxaline backbone and different halogenated end-groups on optical, electrochemical, and photovoltaic performances of organic solar cells (OSCs) are studied. In comparison with TPQ-eC7-4Cl, TPQ-eC7-4F exhibits blue-shifted absorptions with higher molar extinction coefficients in the film state as well as in the donor/acceptor (D/A) blend film state and up-shifting lowest unoccupied molecular orbital (LUMO) energy level. As a result, the OSC devices based on the PBDB-T:TPQ-eC7-4F display an outstanding power conversion efficiency (PCE) of 15.83% with a simultaneously increased open-circuit voltage (V oc) of 0.85 V, a short-circuit current-density (J sc) of 25.89 mA cm–2, and a fill factor (FF) of 72.20%, whereas the PBDB-T:TPQ-eC7-4Cl-based OSC device shows a decent PCE of 14.48% with a V oc of 0.84 V, a J sc of 24.56 mA/cm2, and an FF of 69.77%. To the best of our knowledge, this is the highest photovoltaic performance of PBDB-T-based single-junction binary-OSCs. In comparison, ascribed to the high crystallinity and low solubility of BTP-eC7-4Cl, the corresponding PBDB-T:BTP-eC7-4Cl-based OSC device shows poor photovoltaic performance (PCE of 11.87%). The experimental results demonstrate that fine-tuning the fused quinoxaline backbone with alkyl-chain and end-group functionalization are promising strategies to construct high-performance NFAs for PBDB-T-based single-junction binary-OSCs.

Eco-Friendly Solvent-Processed Dithienosilicon-Bridged Carbazole-Based Small-Molecule Acceptors Achieved over 25.7% PCE in Ternary Devices under Indoor Conditions

“…The charge carrier mobilities of PM7:DTSiC-4F, PM7:DTSiC-2M, and PM7:DTSiCODe-4F binary and PTO2:PM7:DTSiC-4F ternary blends are measured by the space charge limited current (SCLC) method. The device configuration of ITO/PEDOT:PSS/active layer/Au and ITO/ZnO/active layer/Al is used to evaluate the hole and electron transport properties, respectively . The SCLC fitting plots of hole-only (μ h ) and electron-only (μ e ) devices of all blends are depicted in Figure a,b.…”

“…The device configuration of ITO/ PEDOT:PSS/active layer/Au and ITO/ZnO/active layer/Al is used to evaluate the hole and electron transport properties, respectively. 63 The SCLC fitting plots of hole-only (μ h ) and electron-only (μ e ) devices of all blends are depicted in Figure 4a,b , respectively. The ternary blend PTO2:PM7:DTSiC-4F shows the highest and rather well-balanced mobilities.…”

Selective halogenation of central and end-units of nonfullerene acceptors enables enhanced molecular packing and photovoltaic performance

“…16 Numerous strategies, including central subunit replacement (D or A 0 ), [21][22][23][24][25] endgroup modification, [26][27][28][29] and side-chain engineering, [17][18][19]30 were developed to optimize the properties of NFAs. Among these design strategies, halogenation (e.g., fluorination and chlorination) on NFAs has been proven to be an effective approach for improving their photovoltaic performance, 24,31,32 which contributes to (i) tuning the physicochemical properties (e.g., energy levels and absorption spectra); 33,34 (ii) decreasing energy loss; 35,36 and (iii) modulating molecular packing behaviors and crystallization and thus optimizing film morphology. 26,31 However, the halogenation of Y-series NFAs was extensively directed at end groups mainly due to the lack of reactive sites on the benzothiadiazole central unit.…”

“…, fluorination and chlorination) on NFAs has been proven to be an effective approach for improving their photovoltaic performance, 24,31,32 which contributes to (i) tuning the physicochemical properties ( e.g. , energy levels and absorption spectra); 33,34 (ii) decreasing energy loss; 35,36 and (iii) modulating molecular packing behaviors and crystallization and thus optimizing film morphology. 26,31 However, the halogenation of Y-series NFAs was extensively directed at end groups mainly due to the lack of reactive sites on the benzothiadiazole central unit.…”

Phenoxy Group-Containing Asymmetric Non-Fullerene Acceptors Achieved Higher VOC over 1.0 V through Alkoxy Side-Chain Engineering for Organic Solar Cells

“…Over the past 2 decades, bulk heterojunction (BHJ) organic solar cells (OSCs) have attracted great attention because of their superiorities of being low-cost, lightweight, flexible, eco-friendly, and capable of solution-processing fabrication compared with conventional silicon-based SCs. − In recent years, the BHJ photoactive layer containing polymer donors and non-fullerene acceptors (NFAs) has made great progress in the OSCs field. − Since the evolution of the Y6, a variety of Y6-based derivatives have been developed by modifying the side chains, end groups, central backbones, and atoms on the backbone. − As a result, OSC devices have been significantly improved with power conversion efficiencies (PCEs) of over 19%. − …”