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The ternary strategy has proven to be an effective method for improving the efficiency of organic solar cells (OSCs). However, designing and selecting the third component still pose challenges. In this study, this issue is addressed by focusing on the PBDB‐T:Y18‐F binary system and introducing a new, strong luminescent, asymmetric small‐molecule acceptor (SMA) called L8‐CBIC‐Cl, which shares a similar skeleton with Y18‐F. The similarity in molecular framework facilitates good compatibility between the two acceptors, resulting in the formation of an alloy‐like acceptor phase. Furthermore, the norbornenyl‐modified end group in L8‐CBIC‐Cl contributes to its strong luminescent properties, which in turn leads to a low non‐radiative energy loss and a high open‐circuit voltage. Consequently, the PBDB‐T:L8‐CBIC‐Cl:Y18‐F based ternary devices realize a high power conversion efficiency (PCE) up to 17.01%, which is higher than PBDB‐T:Y18‐F device (14.49%). Importantly, L8‐CBIC‐Cl exhibits a good universality as a guest acceptor in other three binary systems (D18:Y6, D18:BTP‐eC9‐4F, and D18:L8‐BO). The D18:L8‐BO:L8‐CBIC‐Cl device shows an impressive efficiency of 19%. The work demonstrates that employing SMA with a high PLQY and better miscibility with host acceptor as the third component has a great potential for developing high‐efficiency ternary OSCs. [ABSTRACT FROM AUTHOR]

Utilizing intermolecular hydrogen‐bonding interactions stands for an effective approach in advancing the efficiency and stability of small‐molecule acceptors (SMAs) for polymer solar cells. Herein, we synthesized three SMAs (Qo1, Qo2, and Qo3) using indeno[1,2‐b]quinoxalin‐11‐one (Qox) as the electron‐deficient group, with the incorporation of a methylation strategy. Through crystallographic analysis, it is observed that two Qox‐based methylated acceptors (Qo2 and Qo3) exhibit multiple hydrogen bond‐assisted 3D network transport structures, in contrast to the 2D transport structure observed in gem‐dichlorinated counterpart (Qo4). Notably, Qo2 exhibits multiple and stronger hydrogen‐bonding interactions compared with Qo3. Consequently, PM6 : Qo2 device realizes the highest power conversion efficiency (PCE) of 18.4 %, surpassing the efficiencies of devices based on Qo1 (15.8 %), Qo3 (16.7 %), and Qo4 (2.4 %). This remarkable PCE in PM6 : Qo2 device can be primarily ascribed to the enhanced donor‐acceptor miscibility, more favorable medium structure, and more efficient charge transfer and collection behavior. Moreover, the PM6 : Qo2 device demonstrates exceptional thermal stability, retaining 82.8 % of its initial PCE after undergoing annealing at 65 °C for 250 hours. Our research showcases that precise methylation, particularly targeting the formation of intermolecular hydrogen‐bonding interactions to tune crystal packing patterns, represents a promising strategy in the molecular design of efficient and stable SMAs. [ABSTRACT FROM AUTHOR]

In this work, inspired by the principles of a pressure cooker, we utilized a high‐pressure method to address the processing challenges associated with high molecular weight polymers. Through this approach, we successfully dissolved high molecular weight D18 in chloroform at 100 °C within a pressure‐tight vial. The increased steam pressure raised the boiling point and dissolving capacity of chloroform, enabling the creation of a hybrid film with superior properties, including more ordered molecular arrangement, increased crystallinity, extended exciton diffusion length, and improved phase morphology. Organic solar cells (OSCs) based on D18 : L8‐BO prepared using this high‐pressure method achieved an outstanding power conversion efficiency of 19.65 %, setting a new record for binary devices to date. Furthermore, this high‐pressure method was successfully applied to fabricate OSCs based on other common systems, leading to significant enhancements in device performance. In summary, this research introduces a universal method for processing high molecular weight D18 materials, ultimately resulting in the highest performance reported for binary organic solar cells. [ABSTRACT FROM AUTHOR]

Although the advances in organic solar cells (OSCs) have been considerable, their efficiency is still limited by recombination losses. Photogenerated electrons and holes are generally bound as localized excitons in organic semiconductors. The transition from excitons into free charges requires diffusion and dissociation processes, in which parasitic recombination losses exist. Reducing these losses is necessary for highly efficient OSCs. The crystallization behavior of the active layers can influence the efficiency of exciton diffusion and dissociation. In this work, different additives are delicately designed to control the crystallization behavior. It is found that the crystallization quality of active layers can be improved by controlling the aggregation of nonfullerene acceptors. The π–π stacking of blend films becomes compact, meanwhile, the crystallization in the vertical direction is more uniform. These are beneficial to the diffusion and dissociation of excitons. As a consequence, recombination losses are reduced and power convention efficiencies (PCEs) are improved significantly. Meanwhile, the general applicability of the additive is demonstrated in various organic photovoltaic systems, in which a PCE of 19.3% is achieved in D18:BTP‐eC9‐4F OSCs. This work provides a facile strategy to reduce the recombination losses of excitons for efficient devices. [ABSTRACT FROM AUTHOR]

Nowadays, it is still a great challenge to obtain high‐performance green‐solvent‐processed organic solar cells (OSCs). In this study, a ternary blend strategy (one donor and two acceptors, 1D/2A) is developed to solve the difficulty of film morphology modulation during the fabrication of high‐performance green‐solvent‐processed OSCs. A typical high‐performance halogenated‐solvent processable binary system D18:BTP‐eC9‐4F is selected as the host, its green‐solvents‐processed devices show an inferior power conversion efficiency (PCE) of ≈16%. SM16 with two 3D shape persistent end groups is selected as the third component due to its high fluorescence quantum yield, reduced intermolecular interaction, good solubility, and moderate crystallinity. As a result, the ternary devices display bicontinuous interpenetrating networks, reduced energy loss, and suppressed charge carrier recombination losses. Hence, an excellent PCE of 18.20% is achieved for the D18:BTP‐eC9‐4F:SM16 ternary devices, which is much higher than D18:BTP‐eC9‐4F‐based binary ones and also one of the highest PCEs for the green‐solvents‐processed OSCs. Besides, this strategy also demonstrates a good universality for other binary systems and becomes an effective pathway for the development of green‐solvent processable high‐performance OSCs. [ABSTRACT FROM AUTHOR]

Three terpolymer donors (PL1, PL2, and PL3) employing repeating units of two popular photovoltaic polymers PM6 and D18 are synthesized by random copolymerization. The terpolymers can reduce the regio‐regularity of the polymer backbones and endow them with much‐enhanced solubility in nonhalogenated solvents such as o‐xylene. Furthermore, along with the appearance of temperature‐dependent aggregation behavior, indicating the adaptability for fabricating organic solar cells (OSCs) by eco‐friendly solvent processing. Among them, PL1‐based OSCs display higher and more balanced hole and electron mobilities, longer charge separation exciton lifetime, and better exciton dissociation and charge collection capabilities than the parent polymers (PM6 and D18) based ones. A power conversion efficiency of 18.14% with a very low energy loss is achieved based on terpolymer PL1, which is much higher than that of PM6 (15.16%) and D18 (16.18%). The result provides an effective way to realize high‐performance nonhalogenated processing polymer donor materials. [ABSTRACT FROM AUTHOR]

The ionic nature of organic trihalide perovskite leads to structural irregularity and energy disorder at the perovskite surface, which seriously affects the photovoltaic performance of perovskite solar cells. Here, the origin of the perovskite surface disorder is analyzed, and a facial ion‐exchange strategy is designed to regulate the surface chemical environment. By the reconstruction of terminal irregular Pb–I bonds and random cations, the repaired surface is characteristic of the reduced band tail states, consequent to the suppression of the uplift of quasi‐Fermi level splitting and photocarrier scattering. The optimized device gets a high open‐circuit voltage and operational stability. These findings fully elaborate the underlying mechanism concerning perovskite surface problem, giving guidance on tailoring the energy disorder. [ABSTRACT FROM AUTHOR]

• Cyclopropylcarbamidine hydrochloride is applied onto the surface of FAPbI 3 perovskite film for defects passivation. • With optimized energy levels, a peak PCE of 22.8% with an optimal voltage loss of 0.34 eV is achieved. • The hydrophobicity of the 2D passivation layer contributes to the enhancement of device stability. [Display omitted] Here, we demonstrate cyclopropylcarbamidine hydrochloride (CPAH) as a novel organic halide salt to construct 2D layer for surface passivation of phase-pure FAPbI 3 film. The results verify that the introduction of 2D passivation layer is beneficial to the suppression of charge recombination and the promotion of charge transfer. With prolonged charge carrier lifetime and optimized energy levels, an impressive PCE of 22.8% is obtained for the as-prepared planar devices based on 3D FAPbI 3 /2D (CPA) 2 PbI 2 Cl 2 , along with simultaneous enhancement of open circuit voltage and fill factor. The optimal voltage loss is controlled to be 0.34 eV. What's more, the 2D layer-containing unencapsulated devices show significantly enhanced wet-, thermal- and light stability. Our findings further pave the way of utilizing novel organic halide salts for 2D perovskite construction, which provides a deeply investigated route for the fabrication of efficient and stable perovskite solar cells. [ABSTRACT FROM AUTHOR]