NIR-Absorbing Electron Acceptor Based on a Selenium-Heterocyclic Core Attaching to Phenylalkyl Side Chains for Polymer Solar Cells with 17.3% Efficiency

Abstract

Selenium-heterocyclic and side-chain strategies for developing near-infrared (NIR) small fused-ring acceptors (FRAs) to further obtain short-circuit current density (J sc ) have proven advantageous in the top-performing polymer solar cells (PSCs). Herein, a new electron-rich central selenium-containing heterocycle core (BTSe) attaching alkyl side chains with a terminal phenyl group was coupled with a difluorinated and dichlorinated electron-accepting terminal 1,1-dicyanomethylene-3-indanone (IC) to afford two types of new FRAs, BTSe-IC2F and BTSe-IC2Cl. Interestingly, in spite of the weaker intramolecular charge transfer, BTSe-IC2F shows a stronger NIR response because of the smaller bandgap (E g opt ) up to 1.26 eV, benefiting from the stronger ordered molecular packing in comparison to BTSe-IC2Cl with an E g opt of 1.30 eV. Additionally, thermal annealing induced an evident red shift by ∼50 nm in the absorption of D18:BTSe-IC2F blend films. Such a phenomenon may be attributed to the synergistic impact of the formation of inward constriction toward the molecular backbone because of the combination of bulky side chains and fluorinated IC as well as the reduced aromaticity of the selenium heterocycle. Consequently, the thermally annealed device based on BTSe-IC2F/D18 achieves a champion power conversion efficiency (PCE) of 17.3% with a high fill factor (FF) of 77.22%, which is among the highest reported PCE values for selenium-heterocyclic FRAs in binary PSCs. The improved J sc and FF values of the D18:BTSe-IC2F film are simultaneously achieved mainly because of the preferred face-on orientations, the wellbalanced electron/hole mobility, and the favorable blend morphology compared to D18:BTSe-IC2Cl. This work suggests that the selenium-heterocyclic fused-ring core (with proper side chains) combined with fluorinated terminal groups is an effective strategy for obtaining highly efficient NIR-responsive FRAs.

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

“…Compared with TPQ-eC7-4F, a 20 nm red-shift in TPQ-eC7-4Cl absorption spectrum is observed, which is ascribed to the stronger ICT effect between the fused donor core and 2Cl-IC end-group acceptor. These features imply that TPQ-eC7-4F shows weaker molecular aggregation compared with TPQ-eC7-4Cl . The film state absorption maxima (λ max ) of TPQ-eC7-4F, TPQ-eC7-4Cl, and BTP-eC7-4Cl are observed at 798, 822, and 825 nm, respectively (Figure b), which can be ascribed to the strong intermolecular π–π-stacking.…”

“…These features imply that TPQ-eC7-4F shows weaker molecular aggregation compared with TPQ-eC7-4Cl. 61 The film state absorption maxima (λ max ) of TPQ-eC7-4F, TPQ-eC7-4Cl, and BTP-eC7-4Cl are observed at 798, 822, and 825 nm, respectively (Figure 3b), which can be ascribed to the strong intermolecular π−π-stacking. The molar extinction coefficient of the TPQ-eC7-4F is higher than the TPQ-eC7-4Cl, implying that TPQ-eC7-4F exhibits strong intermolecular interaction between acceptor molecules and more ordered molecular packing in the film state.…”

Intrinsic influence of selenium substitution in thiophene and benzo-2,1,3-thiadiazole on the electronic structure, excited states and photovoltaic performances evaluated using theoretical calculations

“…Electrostatic potentials (ESPs) were further used to display the 3D charge distributions and all the spatial positions of the electron-deficient and electron-rich studied NFAs. 24 The ESP distribution on the donor core of NFAs gradually changed from red to white and blue, indicating that the ESP value changed from positive to negative due to the stronger ICT caused by the selenium substitution. 62 Fig.…”

“…Therefore, it can be stated that selenization is a powerful modification strategy that has a positive effect on the long-term operational stability of bulk heterojunction OSC devices and can significantly extend the life of the device. 22–24…”

One-Pot Multicomponent Polymerization, Metal-, and Non-Metal-Catalyzed Synthesis of Organoselenium Compounds

“…Accordingly, OSe compounds are known for their ability to react with O 2 -free radicals and thus prevent the progression of oxidative stress-related diseases [ 3 , 6 , 10 , 14 ]. Furthermore, OSe compounds were also used in material science due to their semiconductor potential and therefore used in sodium-ion batteries, solar cells, and H 2 evolution catalysts [ 2 , 15 , 16 , 17 ]. Moreover, the Se center is present in many naturally occurring and bioactive interesting OSe compounds ( Figure 1 ), such as the selenoaminoacids (e.g., selenocysteine ( I ), selenomethionine ( II ), and selenocystine ( III )) [ 18 , 19 , 20 ].…”