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Trap states in organic solar cells (OSCs) can capture free charges, leading to a reduction in current density and significant energy loss. Since charge collection is primarily dependent on the interface layer, minimizing trap states at interfaces can effectively suppress energy losses, a topic that has been rarely explored. Herein, an interface strategy is proposed by combining Me‐4PACz and PEDOT:PSS to mitigate the trap‐assisted nonradiative recombination at the hole transport layer (HTL). OSCs based on the Me‐4PACz/PEDOT:PSS exhibit reduced trap densities and low energy losses compared to devices fabricated with a single‐layer HTL. This reduction can be attributed to a lower nonradiative recombination rate during hole transport at the interface. Changes in the work function of the two interlayers due to contact result in the existence of a built‐in potential inside the composite interlayer, promoting charge collection and reducing energy loss from charge recombination. Furthermore, the composite HTL interface induces vertical phase separation of active layer, leading to significant improvements of the fill factor for OSCs. As a result, high power conversion efficiencies (PCEs) of 18.70% and 19.02% are achieved for binary all‐polymer solar cells and polymer donor/small molecule acceptor solar cells, respectively. [ABSTRACT FROM AUTHOR]

The development of high‐efficiency organic solar cells (OSCs) processed from non‐halogenated solvents is crucially important for their scale‐up industry production. However, owing to the difficulty of regulating molecular aggregation, there is a huge efficiency gap between non‐halogenated and halogenated solvent processed OSCs. Herein, we fabricate o‐xylene processed OSCs with approaching 20 % efficiency by incorporating a trimeric guest acceptor named Tri‐V into the PM6:L8‐BO‐X host blend. The incorporation of Tri‐V effectively restricts the excessive aggregation of L8‐BO‐X, regulates the molecular packing and optimizes the phase‐separation morphology, which leads to mitigated trap density states, reduced energy loss and suppressed charge recombination. Consequently, the PM6:L8‐BO‐X:Tri‐V‐based device achieves an efficiency of 19.82 %, representing the highest efficiency for non‐halogenated solvent‐processed OSCs reported to date. Noticeably, with the addition of Tri‐V, the ternary device shows an improved photostability than binary PM6:L8‐BO‐X‐based device, and maintains 80 % of the initial efficiency after continuous illumination for 1380 h. This work provides a feasible approach for fabricating high‐efficiency, stable, eco‐friendly OSCs, and sheds new light on the large‐scale industrial production of OSCs. [ABSTRACT FROM AUTHOR]

Oligomer acceptors in organic solar cells (OSCs) have garnered substantial attention owing to their impressive power conversion efficiency (PCE) and long‐term stability. However, the simple and efficient synthesis of oligomer acceptors with higher glass transition temperatures (Tg) remains a formidable challenge. In this study, we propose an innovative strategy for the synthesis of tetramers, denoted as Tet‐n, with elevated Tgs, achieved through only two consecutive Stille coupling reactions. Importantly, our strategy significantly reduces the redundancy in reaction steps compared to conventional methods for linear tetramer synthesis, thereby improving both reaction efficiency and yield. Furthermore, the OSC based on PM6:Tet‐1 attains a high PCE of 17.32 %, and the PM6:L8‐BO:Tet‐1 ternary device achieves an even more higher PCE of 19.31 %. Remarkably, the binary device based on the Tet‐1 tetramer demonstrates outstanding operational stability, retaining 80 % of the initial efficiency (T80) even after 1706 h of continuous illumination, which is primarily attributed to the enhanced Tg (247 °C) and lower diffusion coefficient (1.56×10−27 cm2 s−1). This work demonstrates the effectiveness of our proposed approach in the straightforward and efficient synthesis of tetramers materials with higher Tgs, thus offering a viable pathway for developing high‐efficiency and stable OSCs. [ABSTRACT FROM AUTHOR]

Oligomer acceptors have recently emerged as promising photovoltaic materials for achieving high power conversion efficiency (PCE) and long‐term stability in organic solar cells (OSCs). However, the limited availability of diverse acceptors, resulting from the sole synthetic approach, has hindered their potential for future industrialization. In this study, we present a facile and effective stepwise approach that utilizes two consecutive Stille coupling reactions for the synthesis of oligomer acceptors. To demonstrate the feasibility of the novel approach, we successfully synthesize a trimer acceptor, Tri‐Y6‐OD, and further systematically investigate the impact of oligomerization on device performance and stability. The results reveal that this approach has significant advantages compared to the conventional method, including reduced formation of unwanted by‐products and lower difficulties in purification. Remarkably, the OSC based on PM6 : Tri‐Y6‐OD achieves an impressive PCE of 18.03 % and maintains 80 % of the initial PCE (T80) for 1523 h under illumination, surpassing the performance of the corresponding small molecule acceptor Y6‐OD‐based device. Furthermore, the versatility of the synthetic strategy in obtaining diverse acceptors is further demonstrated. Overall, our findings provide a facile, versatile and stepwise way for synthesizing oligomer acceptors, thereby facilitating the development of stable and efficient OSCs. [ABSTRACT FROM AUTHOR]

By changing the structures of the side chain on the backbone of the Y6 acceptor, many Y‐series acceptors have been synthesized to investigate the relationships between structures and properties of the fused‐ring electron acceptors (FREAs). However, not much attention has been paid to the effects of cycloalkane substituents on optoelectronic, morphological, and photovoltaic properties of the FREAs. Here, a brand‐new FREA D12 is developed by incorporating cyclohexylmethyl functional groups into the pyrrole rings of the backbone of the Y6 acceptor, and a similar compound E12 with the linear n‐heptane side chains is also synthesized for comparison. After the cyclization of the alkyl side‐chain, the molecular orientation of D12 exhibits favorable face‐on dominant, which endows D12 with higher charge mobility. Consequently, the organic solar cells (OSCs) with PM6 as donor and D12 as acceptor deliver the maximum power conversion efficiency of 17.3%, along with an excellent fill factor of 0.794, which is much higher than those of the PM6:E12‐based OSCs. The results reveal that introducing an inner cyclized alkyl chain on the pyrrole motif is a simple and feasible strategy to regulate molecular orientation and improve photovoltaic properties, which might provide guidelines for developing high‐performance electron acceptors. [ABSTRACT FROM AUTHOR]

Morphological stability is crucially important for the long‐term stability of polymer solar cells (PSCs). Many high‐efficiency PSCs suffer from metastable morphology, resulting in severe device degradation. Here, a series of copolymers is developed by manipulating the content of chlorinated benzodithiophene‐4,8‐dione (T1‐Cl) via a random copolymerization approach. It is found that all the copolymers can self‐assemble into a fibril nanostructure in films. By altering the T1‐Cl content, the polymer crystallinity and fibril width can be effectively controlled. When blended with several nonfullerene acceptors, such as TTPTT‐4F, O‐INIC3, EH‐INIC3, and Y6, the optimized fibril interpenetrating morphology can not only favor charge transport, but also inhibit the unfavorable molecular diffusion and aggregation in active layers, leading to excellent morphological stability. The work demonstrates the importance of optimization of fibril network morphology in realizing high‐efficiency and ambient‐stable PSCs, and also provides new insights into the effect of chemical structure on the fibril network morphology and photovoltaic performance of PSCs. [ABSTRACT FROM AUTHOR]

This study reports on the synthesis of an indancenodithiophene perylene diimide tetramer via unique direct (hetero)arylation reactivity. The thiophene based core structure is shown to be easily functionalized with four perylene diimides at the four active C–H positions. This new reactivity provides a simple synthetic pathway towards tetrameric perylene diimides which have emerged as one of the best classes of electron acceptors for organic solar cells. [ABSTRACT FROM AUTHOR]

In this work, the fluorine substituted benzotriazole (FBTz) unit is introduced into terpolymers for the first time. FBTz as an acceptor unit was added to the terpolymers of PTT-FBTz and PTTz-FBTz, in which the bithiophene (biTh) unit is used as the donor unit and thieno[3,2- b ]thiophene (TT) or thiazolo[5,4- d ]thiazole (TTz) is adopted as a third component, respectively. Compared to PTT-FBTz with TT as the third component, PTTz-FBTz with TTz showed pronounced aggregated shoulder peaks both in solution and film absorption spectra. Electrochemical cyclic voltammetry (CV) shows PTTz-FBTz possesses both lower HOMO/LUMO level than PTT-FBTz due to the higher electronegativity of nitrogen atoms in TTz unit. Subsequently, the bulk-heterojunction polymer solar cells (PSCs) based on PTTz-FBTz show a higher power conversion efficiency of 7.03%, which is much higher than those of PTT-FBTz based devices (PCE = 2.63%). The enhancement of photovoltaic performance based on PTTz-FBTz is mainly attributed to the deeper highest occupied molecular orbital (HOMO) level, higher carrier transport and better molecular packing. [ABSTRACT FROM AUTHOR]

Reduction of non‐radiative energy loss (ΔEnr) in all‐polymer solar cells (all‐PSCs) is crucially important for achieving high power conversion efficiencies (PCEs). Herein, an efficient strategy is reported to reduce the ΔEnr by introducing luminescent unit into the backbone of polymer acceptors. Compared to the device based on PM6:PYDT, the ΔEnr in all‐PSC based on PM6:PYDT‐CzP‐9 has decreased from 0.188 to 0.183 eV. This reduction is attributed to the improvement in electroluminescence external quantum efficiency (EQEEL). The PM6:PYDT‐CzP‐9 device has shown an 18% increase in EQEEL compared to the device based on PM6:PYDT (8.4 × 10−4 vs 7.1 × 10−4), demonstrating that the incorporation of luminescent unit in polymer acceptors is highly effective in enhancing the electroluminescence performance of all‐PSCs. As a result, the PM6:PYDT‐CzP‐9 device yielded a high VOC of 0.967 V, without the sacrifice of short‐circuit current density (23.42 mA cm−2) and fill factor (77.5%), leading to a high PCE of 17.55%. [ABSTRACT FROM AUTHOR]

Strong electron‐phonon coupling can hinder exciton transport and induce undesirable non‐radiative recombination, resulting in a shortened exciton diffusion distance and constrained exciton dissociation in organic solar cells (OSCs). Therefore, suppressing electron‐phonon coupling is crucially important for achieveing high‐performance OSCs. Here, we employ the solid additive to regulating electron‐phonon coupling in OSCs. The planar configuration of SA1 confers a significant advantage in suppressing lattice vibrations in the active layers, reducing the scattering of excitons by phonons. Consequently, a slow but sustained hole transfer process is identified in the SA1‐assisted film, indicating an enhancement in hole transfer efficiency. Prolonged exciton diffusion length and exciton lifetime are achieved in the blend film processed with SA1, attributed to a low non‐radiative recombination rate and low energetic disorder for charge carrier transport. As a result, a high efficiency of 20 % was achieved for ternary device with a remarkable short‐circuit current. This work highlights the important role of suppressing electron‐phonon coupling in improving the photovoltaic performance of OSCs. [ABSTRACT FROM AUTHOR]