Large energy loss is one of the main limiting factors for power conversion efficiencies (PCEs) of organic solar cells (OSCs). To this effect, the chemical modifications of the famous Y‐series nonfullerene acceptor (NFA) BTP‐4Cl‐BO with a new end group, TPC‐Cl, whose π‐conjugation is extended through the fusing of 3‐(dicyanomethylene)indanone (IC) group with a chlorinated thiophene ring, to synthesize two novel NFAs, BTP‐T‐2Cl and BTP‐T‐3Cl are performed. For BTP‐T‐2Cl with two TPC‐Cl groups, the resulting OSC exhibits a modest PCE of 14.89% but an extraordinary low energy loss of 0.49 eV, because its superior electroluminescence quantum efficiency of 0.0606% mitigates significantly the nonradiative loss (0.191 eV). For BTP‐T‐3Cl with one TPC‐Cl group, the corresponding device shows a higher PCE of 17.61% accompanied by a slightly bigger energy loss of 0.51 eV, which can be ascribed to the optimized morphology and/or efficient charge generation. Furthermore, the ternary OSC adopting two NFAs of BTP‐T‐3Cl and BTP‐4Cl‐BO achieves an impressive PCE of 18.21% (certified value of 17.9%), which is among the highest values for OSCs to date. The above results demonstrate that expanding end groups of NFAs with electron‐donating rings is an effective strategy to realize lower energy losses for OSCs.

Developing indium‐tin‐oxide (ITO)‐free flexible organic photovoltaics (OPVs) with upscaling capacity is of great significance for practical applications of OPVs. Unfortunately, the efficiencies of the corresponding devices lag far behind those of ITO‐based rigid small‐area counterparts. To address this issue, an advanced device configuration is designed and fabricated featuring a top‐illuminated structure with ultrathin Ag as the transparent electrode. First, a conjugated polyelectrolyte layer, i.e., PCP‐Li, is inserted to effectively connect the bottom Ag anode and the hole transport layer, achieving good photon to electron conversion. Second, charge collecting grids are deposited to suppress the increased resistance loss with the upscaling of the device area, realizing almost full retention of device efficiency from 0.06 to 1 cm2. Third, the designed device delivers the best efficiency of 15.56% with the area of 1 cm2 on polyimide substrate, representing as the record among the ITO‐free, large‐area, flexible OPVs. Interestingly, the device exhibits no degradation after 100 000 bending cycles with a radius of 4 mm, which is the best result for flexible OPVs. This work provides insight into device structure design and optimization for OPVs with high efficiency, low cost, superior flexibility, and upscaling capacity, indicating the potential for the future commercialization of OPVs.

Morphology is of great significance to the performance of organic solar cells (OSCs), since appropriate morphology could not only promote the exciton dissociation, but also reduce the charge recombination. In this work, we have developed a solid additive-assisted layer-by-layer (SAA-LBL) processing to fabricate high-efficiency OSCs. By adding the solid additive of fatty acid (FA) into polymer donor PM6 solution, controllable pre-phase separation forms between PM6 and FA. This intermixed morphology facilitates the diffusion of acceptor Y6 into the donor PM6 during the LBL processing, due to the good miscibility and fast-solvation of the FA with chloroform solution dripping. Interestingly, this results in the desired morphology with refined phase-separated domain and vertical phase-separation structure to better balance the charge transport /collection and exciton dissociation. Consequently, the binary single junction OSCs based on PM6:Y6 blend reach champion power conversion efficiency (PCE) of 18.16% with SAA-LBL processing, which can be generally applicable to diverse systems, e.g., the PM6:L8-BO-based devices and thick-film devices. The efficacy of SAA-LBL is confirmed in binary OSCs based on PM6:L8-BO, where record PCEs of 19.02% and 16.44% are realized for devices with 100 and 250 nm active layers, respectively. The work provides a simple but effective way to control the morphology for high-efficiency OSCs and demonstrates the SAA-LBL processing a promising methodology for boosting the industrial manufacturing of OSCs.

An A–D–D–A-type near-infrared non-fullerene small-molecule acceptor IDT2-DFIC with indacenodithiophene–indacenodithiophene (IDT2) as donating core and 2-(5,6-difluoro-3-oxo-2,3-dihydro-1H-inden-1-ylidene)malononitrile (2FIC) as electron withdrawing end groups has been synthesized.

Organic solar cells (OSCs) show the potential to harness solar energy at a lower cost and in a greener way with the merits of mechanical flexibility and potential low-cost upscaling production with solution processing. Meanwhile, the common use of toxic halogenated solvents causes pollution to the natural environment, and thus, needs to be avoided. Following the authors' previous work on the design of top-illuminated ultrathin Ag-based device structure highlighting most merits of OSC, herein non-halogen solvent and additive processing OSCs are presented, which exhibit high power conversion efficiency (PCE) of 17.64%, close to the best PCE with the commonly used halogen solvent. Interestingly, it is observed that the additive and the multicomponent strategy (blending third component BTP-S2 into PM6:L8-BO binary blend) synergistically affect the optimal morphology and device performance. Finally, OSC devices featuring green solvent processing, indium tin oxide-free, flexibility, and upscaling merits are fabricated and exhibit the best PCE of 13.76% with high mechanical robustness and good stability against heat or light illumination. This work provides a prospective potential for manufacturing the OSC toward practical applications.

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Self‐assembly monolayers (SAMs) of small molecules are attractive alternatives of traditional transporting materials to reconcile interfaces with tunable interface properties in polymer solar cells (PSCs). Herein, it is found that benzylphosphonic acid (BnPA)/pentafluorobenzylphosphonic acid (F5BnPA) mixture could form an ordered SAM on indium tin oxide (ITO) due to the strong arene–perfluoroarene interaction, thus the hole‐transport‐layer‐free PSCs based on poly[(2,6‐(4,8‐bis(5‐(2‐ethylhexyl‐3‐fluoro)thiophen‐2‐yl)‐benzo[1,2‐b:4,5‐b′]‐dithiophene))‐alt‐(5,5‐(1′,3′‐di‐2‐thienyl‐5′,7′‐bis(2‐ethylhexyl)benzo[1′,2′‐c:4′,5′‐c′]dithiophene‐4,8‐dione)] (PM6): BO‐4Cl achieves a power conversion efficiency (PCE) of 18.0%. The high performance is attributed to the improved energy level alignment, excellent carrier‐extraction ability, and reduced recombination. The device also shows much better stability compared with the devices based on BnPA‐ or F5BnPA‐modified ITO, and shows comparable stability to the device based on ITO/poly(3,4‐ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS). Furthermore, the device with an area of 1.05 cm2 shows a PCE of 15.3%, which is among the highest reported values. Herein, the potential of SAMs is highlighted for highly stable and high‐performance PSCs toward commercialization.