Selenophene substitution of photovoltaics materials can improve their intermolecular interaction, and thus offer a good opportunity to finely optimize their phase separation morphology to an ideal state. However, the performance...

small-molecule acceptor are currently attracting enormous attentions due to their distinct advantages such as monodispersion, easy purification, and scalability with negligible batch-to-batch variation. [1][2][3][4][5] Tremendous progress has been made in the past years on rational molecule design, device engineering, and interface modification, leading to over 10% power conversion efficiencies (PCEs) in ASM OSCs with fullerene derivatives as the electron acceptor. [6][7][8][9] However, the difficulties of controlling the morphology (e.g., crystallinity and domain size) of active-layer constrained the development of ASM OSCs. [10][11][12] Furthermore, the device performance of ASM OSCs is often sensitive to the film thickness of ≈100 nm in most reports, which hinders the future high-throughput device fabrication processing like roll-to-roll and ink jet printings. [13][14][15] Thus, it is worth finding an effective method to tune the active-layer morphology, and attain high efficiency with thick active layers. Benzodithiophene terthiophene rhodanine (BTR) stands out as an excellent thickfilm OSC material with respectable (while not enough) efficiency of over 9% pairing with fullerene acceptor. Finding effective methods to further enhancing the BTR based thickfilm OSC device efficiency is expected to be an important and Thick-film all-small-molecule (ASM) organic solar cells (OSCs) are preferred for large-scale fabrication with printing techniques due to the distinct advantages of monodispersion, easy purification, and negligible batch-to-batch variation. However, ASM OSCs are typically constrained by the morphology aspect to achieve high efficiency and maintain thick film simultaneously. Specifically, synchronously manipulating crystallinity, domain size, and phase segregation to a suitable level are extremely challenging. Herein, a derivative of benzodithiophene terthiophene rhodanine (BTR) (a successful small molecule donor for thick-film OSCs), namely, BTR-OH, is synthesized with similar chemical structure and absorption but less crystallinity relative to BTR, and is employed as a third component to construct BTR:BTR-OH:PC 71 BM ternary devices. The power conversion efficiency (PCE) of 10.14% and fill factor (FF) of 74.2% are successfully obtained in ≈300 nm OSC, which outperforms BTR:PC 71 BM (9.05% and 69.6%) and BTR-OH:PC 71 BM (8.00% and 65.3%) counterparts, and stands among the top values for thick-film ASM OSCs. The performance enhancement results from the enhanced absorption, suppressed bimolecular/trap-assisted recombination, improved charge extraction, optimized domain size, and suitable crystallinity. These findings demonstrate that the donor derivative featuring similar chemical structure but different crystallinity provides a promising third component guideline for highperformance ternary ASM OSCs. Organic Solar Cells

Achieving an ideal morphology is an imperative avenue for enhancing key parameters toward high‐performing organic solar cells (OSCs). Among a myriad of morphological‐control methods, the strategy of incorporating a third component with structural similarity and crystallinity difference to construct ternary OSCs has emerged as an effective approach to regulate morphology. A nematic liquid‐crystalline benzodithiophene terthiophene rhodamine (BTR) molecule, which possesses the same alkylthio‐thienyl‐substituted benzo moiety but obviously stronger crystallinity compared to classical medium‐bandgap polymeric donor PM6, is employed as a third component to construct ternary OSCs based on a PM6:BTR:Y6 system. The doping of BTR (5 wt%) is found to be enough to improve the OSC morphology—significantly enhancing the crystallinity of the photoactive layer while slightly reducing the donor/acceptor phase separation scale simultaneously. Rarely is such a morphology evolution reported. It positively affects the electronic properties of the device—prolongs the carrier lifetime, shortens the photocurrent decay time, facilitates exciton dissociation, charge transport, and collection, and ultimately boosts the power conversion efficiency from 15.7% to 16.6%. This result demonstrates that the successful synergy of liquid‐crystalline small‐molecule and polymeric donors delicately adjusts the active‐layer morphology and refines device performance, which brings vibrancy to the OSC research field.

Nonfullerene acceptors (NFAs) based on calamitic-shaped small molecules are being developed rapidly to improve the photoelectron conversion efficiencies (PCEs) of organic solar cells. NFAs with light absorption extended to the near-infrared (NIR) region are of interest because they play a pivotal role in both organic tandem cells and semitransparent devices. In this work, two simple acceptor−donor−acceptor-structured NFAs (CPDT-4Cl and CPDT-4F) have been designed and synthesized. Featured with dimerized 4H-cyclopenta[1,2-b:5,4-b′]dithiophene (CPDT) as the electron-donating core and Cl-or F-substituted 2-(3-oxo-2,3-dihydro-1Hinden-1-ylidene)malononitrile as the electron-accepting unit, the absorption spectra of two NFAs are extended to the NIR region with an absorption edge at approximately 910 nm. In conjunction with the polymer donor material PBDB-T, a PCE of 9.47% was achieved by using a CPDT-4F-based device with a short-circuit current density of up to 20.1 mA/ cm 2 , which slightly outperforms its counterpart CPDT-4Cl (PCE = 9.28%) under the same condition. This work broadens the scope of developing new NIR NFAs with both high efficiency and easy accessibility.