Achieving Record-Efficiency Organic Solar Cells upon Tuning the Conformation of Solid Additives

Abstract

Volatile solid additives (SADs) are considered as a simple yet effective approach to tune the film morphology for high-performance organic solar cells (OSCs). However, the structural effects of the SADs on the photovoltaic performance are still elusive. Herein, two volatilizable SADs were designed and synthesized. One is SAD1 with twisted conformation, while the other one is planar SAD2 with the S···O noncovalent intramolecular interactions (NIIs). The theoretical and experimental results revealed that the planar SAD2 with smaller space occupation can more easily insert between the Y6 molecules, which is beneficial to form a tighter intermolecular packing mode of Y6 after thermal treatment. As a result, the SAD2-treated OSCs exhibited less recombination loss, more balanced charge mobility, higher hole transfer rate, and more favorable morphology, resulting in a record power conversion efficiency (PCE) of 18.85% (certified PCE: 18.7%) for single-junction binary OSCs. The universality of this study shed light on understanding the conformation effects of SADs on photovoltaic performances of OSCs.

Efficient and Stable Nonfused Ring Small Molecule Acceptors Powered by an Electron Donating Unit for Organic Solar Cells

“…As summarized in Figure 3c, the intensities of the absorption spectra almost kept unchanged after exposure to light for 60 h. Figure 3d exhibits photographs of TPD-TT and TPD-BT films under different times of light exposure; it is obvious that these films remain their original color after 60 h continuous illumination. Compared with the tetrahedron sp 3 bridge carbon containing acceptors like ITIC 45 and ID4F, 18 TPD-TT and TPD-BT exhibit better photostabilities, which could be attributed to the absence of a tetrahedron sp 3 bridge carbon and the utilization of β-alkyl/alkoxy chains on the periphery of the D units. The intrinsic photostabilities could provide additional stabilities for devices based on them.…”

“…The conjugated frameworks of these acceptors are planar, which facilitates charge transfer between molecules. Meanwhile, the sp 3 hybridized bridge carbons (sp 3 -C) on the fused ring are connected with the side chains that are orthogonal to the conjugated backbones to provide steric hindrance, which could inhibit the excessive self-aggregation of acceptors, thus obtaining the ideal active layer morphologies. Combined with an electron-deficient core-based fused ring unit (DA′D) and pyrrole containing donor motif, Zou et al designed a star NFA named Y6 in 2019.…”

“…Solution-processed organic solar cells (OSCs) could be prepared through large-scale printing on flexible substrates, which is expected to be used in the application scenarios that require flexible devices. To date, OSCs have made huge leaps in device performances, and the PCEs for the single-junction devices have reached 18–19%. − These exciting advances could be mainly attributed to the innovation of photoactive materials, in particular the non-fullerene acceptors (NFAs).…”

Solvent annealing for morphology control to realize high efficiency all-small-molecule organic solar cells

“…Solution-processed organic solar cells (OSCs) have emerged as a promising competitor for the next-generation photovoltaic technology due to their low carbon footprint, lightweightness, semitransparency and so on. [1][2][3][4][5][6][7] In particular, all-small-molecule (ASM) OSCs have attracted tremendous industrial interest due to their well-dened chemical structures, high purity, and excellent reproducibility. [8][9][10][11][12] However, defects in the active layer (AL) morphology are a big challenge in enhancing the power conversion efficiencies (PCEs) of ASM-OSCs.…”

“…Thus far, the research community has dedicated great efforts to control morphology to further evaluate PCEs. 4,13,14 Sun et al, in 2021, demonstrated that a volatile additive, namely dihalogenated 1,1-dicyanomethylene-3-indanone (IC-FI), can enhance the PCE of BTR-Cl/N3 based ASM-OSCs from 13.36% to 14.43%. 15 In 2020, our group induced PC 71 BM material as a ternary component into the BTR-Cl/Y6 blend, leading to signicantly enhanced PCEs with an increase in FF from 69.63% to 77.11%.…”