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Benefiting from the synergistic development of material design, device engineering, and the mechanistic understanding of device physics, the certified power conversion efficiencies (PCEs) of single‐junction non‐fullerene organic solar cells (OSCs) have already reached a very high value of exceeding 19%. However, in addition to PCEs, the poor stability is now a challenging obstacle for commercial applications of organic photovoltaics (OPVs). Herein, recent progress made in exploring operational mechanisms, anomalous photoelectric behaviors, and improving long‐term stability in non‐fullerene OSCs are highlighted from a novel and previously largely undiscussed perspective of engineering exciton and charge carrier pathways. Considering the intrinsic connection among multiple temporal‐scale photocarrier dynamics, multi‐length scale morphologies, and photovoltaic performance in OPVs, this review delineates and establishes a comprehensive and in‐depth property‐function relationship for evaluating the actual device stability. Moreover, this review has also provided some valuable photophysical insights into employing the advanced characterization techniques such as transient absorption spectroscopy and time‐resolved fluorescence imagings. Finally, some of the remaining major challenges related to this topic are proposed toward the further advances of enhancing long‐term operational stability in non‐fullerene OSCs. [ABSTRACT FROM AUTHOR]

A diradicaloid molecule with high semiconducting performance is synthesized based on the quinoidal benzo[1,2‐b:4,5‐b′]dithiophene structure. The diradical character is investigated by quantum chemical calculations and variable temperature electron spin resonance. The diode devices based on this molecule show a large change in electric current in magnetic fields below 100 mT with a strong dependence on the measurement temperatures; as the population of the triplet diradicals increases at high temperatures, the magnetoconductance (MC) values increase. As a result, a MC of −19.4% is achieved at 120 °C, which is the largest negative MC observed for organic molecules to date. In contrast, a smaller diradicaloid molecule based on quinoidal thieno[3,2‐b]thiophene without thermally accessible triplet state shows no MC, indicating the essential role of the triplet diradicals. The strong correlation between the MC and the triplet diradical concentrations suggests that the charge conduction in the diradicaloid is suppressed through a spin‐blocking mechanism, which can be controlled through the magnetic modulation of the hyperfine fields. The compound forms high‐crystallinity thin films and has high monopolar electron transport in organic field‐effect transistors, with an average mobility of 1.01 cm2 V−1 s−1 for edge‐cast films. [ABSTRACT FROM AUTHOR]

Ultrathin (thickness less than 10 µm) organic photovoltaics (OPVs) can be applied to power soft robotics and wearable electronics. In addition to high power conversion efficiency, stability under various environmental stresses is crucial for the application of ultrathin OPVs. In this study, the authors realize highly air‐stable and ultrathin (≈3 µm) OPVs that possess high efficiency (15.8%) and an outstanding power‐per‐weight ratio of 33.8 W g−1. Dynamic secondary‐ion mass spectrometry is used to identify Zn diffusion from the electron transport layer zinc oxide (ZnO) to the interface of photoactive layer; this diffusion results in the degradation of the ultrathin OPVs in air. The suppression of the Zn diffusion by a chelating strategy results in stable ultrathin OPVs that maintain 89.6% of their initial efficiency after storage for 1574 h in air at room temperature under dark conditions and 92.4% of their initial efficiency after annealing for 172 h at 85 °C in air under dark conditions. The lightweight and stable OPVs also possess excellent deformability with 87.3% retention of the initial performance after 5000 cycles of a compressing–stretching test with 33% compression. [ABSTRACT FROM AUTHOR]

Surface modification of SiO2 using a catalyst‐free quantitative reaction between an amine and an ethynyl‐π‐extended naphthalenediimide was investigated. A post‐reaction method, in which the catalyst‐free reaction was performed at the surface after the formation of amino‐terminated self‐assembled monolayers (SAMs), resulted in dense, uniform modification of the SiO2 surface with the naphthalenediimide molecules. Both X‐ray reflectivity and angle‐resolved X‐ray photoemission spectroscopy showed consistent results for the layer thickness and density. In contrast, a pre‐reaction method, in which an amino‐silane and the ethynyl‐π‐extended naphthalenediimide reacted first and then formed a SAM, afforded a sparse SAM on the SiO2 surface, probably due to the steric hindrance of the naphthalenediimide moieties. The in situ decoration of the SiO2 surface by a catalyst‐free quantitative reaction offers a facile route for modifying surface properties with various π‐conjugated molecules suitable for many applications. [ABSTRACT FROM AUTHOR]

The nanopatterning of the surfaces of polymer substrates enhances the performances of photovoltaics. Ultraflexible organic photovoltaics (OPVs) are one of the promising energy harvesters for wearable electronics. A reduction in incident light angle dependence while maintaining the power conversion efficiency (PCE) is desirable for wearable electronics devices in which the angle of incident light continuously changes due to the deformation of the device. However, the nanopatterning of the ultrathin polymer substrates of ultraflexible OPVs using the reported methods is challenging because they fatally damage the substrates. Here, the fabrication of ultraflexible OPVs having a low incident light angle dependence while maintaining a PCE of 10.5% by developing ultrathin nanograting polymer substrates is reported. The nanograting‐patterned fluorinated polymer enables the formation of periodic nanograting structures onto the back surface of a 1 µm thick polymer substrate having a pitch of 760 nm and a height of 100 nm, while the opposite surface remains flat after the formation of the planarization layer. Furthermore, with the nanopatterning of the ultrathin substrate, electron‐transporting layer, and active layer, the ultraflexible OPVs exhibit a PCE of 10.8%. The combination of new materials with the developed patterning method is expected to afford even greater performances. [ABSTRACT FROM AUTHOR]

Abstract: Precise control of the molecular arrangements at the interface between the electron donor and acceptor in mixed bulk heterojunctions (BHJs) remains challenging, despite the correlation between structural characteristics and efficiency in organic photovoltaics (OPVs). This study reveals that the substitution patterns of linear and branched alkyl side chains on electron‐donating/‐accepting alternating copolymers can control the positions of an acceptor molecule (C60) around the π‐conjugated main chains in mixed BHJs. Two‐dimensional solid‐state NMR demonstrates a marked difference in the location of C60 in the blend films. A copolymer with an electron‐accepting unit positioned in close proximity to C60 demonstrated higher OPV performance in combination with various fullerene derivatives. This molecular design offers precise control over the interfacial molecular structure, thereby paving the way for overcoming the current limitations of OPVs comprising mixed BHJs. [ABSTRACT FROM AUTHOR]

Abstract: To maximize the short‐circuit current density (JSC) and the open circuit voltage (VOC) simultaneously is a highly important but challenging issue in organic solar cells (OSCs). In this study, a benzotriazole‐based p‐type polymer (J61) and three benzotriazole‐based nonfullerene small molecule acceptors (BTA1‐3) are chosen to investigate the energetic driving force for the efficient charge transfer. The lowest unoccupied molecular orbital (LUMO) energy levels of small molecule acceptors can be fine‐tuned by modifying the end‐capping units, leading to high VOC (1.15–1.30 V) of OSCs. Particularly, the LUMO energy level of BTA3 satisfies the criteria for efficient charge generation, which results in a high VOC of 1.15 V, nearly 65% external quantum efficiency, and a high power conversion efficiency (PCE) of 8.25%. This is one of the highest VOC in the high‐performance OSCs reported to date. The results imply that it is promising to achieve both high JSC and VOC to realize high PCE with the carefully designed nonfullerene acceptors. [ABSTRACT FROM AUTHOR]

Organic solar cells (OSCs) are promising low-cost devices for generating electricity. In addition to fill factor, the short circuit current density ( JSC) and the open circuit voltage ( VOC) are two key factors that have critical influence on the device performance. The energy levels of the donor and acceptor materials are crucial for achieving a high JSC and VOC. However, the interfacial structures between the organic materials substantially affect the JSC and VOC through the energy of the charge transfer (CT) states and the charge separation and recombination reaction kinetics. Here, it is reported that separating the donor and acceptor layer in bilayer OSCs with a thin insulating layer increases the energy of the CT state by weakening the Coulomb interaction at the interface and this also suppresses photoinduced CT and recombination. Although these effects usually increase VOC and decrease JSC, the trade-off is avoided by doping the insulating layer with a dye to utilize the energy transfer process. The increase in VOC without the reduction in JSC enhances the conversion efficiency of the OSCs by 30%. [ABSTRACT FROM AUTHOR]

A new poly(3-butylthiophene) derivative with one terminus functionalized with a 1H,1H,2H,2H,3H,3H-perfluoroundecyl group (P3BT-F17) is synthesized by Ni-catalyzed quasi-living polymerization and the subsequent quenching of living ends by allyl-Grignard reagent and the attachment of a fluoroalkyl chain. The quantitative introduction of fluoroalkyl chain ends is confirmed by matrix-assisted laser desorption/ionization time-of-flight-mass spectrometry (MALDI-TOF-MS), gel-permeation chromatography (GPC), 1H NMR spectroscopy, and X-ray photoelectron spectroscopy (XPS). The electronic properties of P3BT-F17 in solution and its crystalline structure in the solid state are investigated by UV-vis spectroscopy and cyclic voltammetry (CV), and by DSC and X-ray diffraction (XRD) analyses. [ABSTRACT FROM AUTHOR]