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The side‐chain has a significant influence on the optical properties and aggregation behaviors of the organic small molecule acceptors, which becomes an important strategy to optimize the photovoltaic performance of organic solar cells. In this work, we designed and synthesized three brand‐new nonfused ring electron acceptors (NFREAs) OC4‐4Cl‐Ph, OC4‐4Cl‐Th, and OC4‐4Cl‐C8 with hexylbenzene, hexylthiophene, and octyl side chains on the π‐bridge units. Compared with OC4‐4Cl‐Ph and OC4‐4Cl‐Th, OC4‐4Cl‐C8 with linear alkyl side chain has more red‐shift absorption, which is conducive to obtaining higher short‐circuit current density. Additionally, the OC4‐4Cl‐C8 film exhibits a longer exciton diffusion distance, and the D18:OC4‐4Cl‐C8 blend film displays faster hole transfer, weaker bimolecular recombination, and more efficient exciton transport. Furthermore, The D18:OC4‐4Cl‐C8 blend films may effectively form interpenetrating networks that resemble nanofibrils, which can facilitate exciton dissociation and charge transport. Finally, OC4‐4Cl‐C8‐based devices can be created a marvellously power conversion efficiency (PCE) of 16.56%, which is much higher than OC4‐4Cl‐Ph (12.29%)‐ and OC4‐4Cl‐Th‐based (11.00%) ones, being the highest PCE among the NFREA based binary devices. All in all, we have validated that side‐chain engineering is an efficient way to achieve high‐performance NFREAs. [ABSTRACT FROM AUTHOR]

In the development of high‐performance organic solar cells (OSCs), the self‐organization of organic semiconductors plays a crucial role. This study focuses on the precisely manipulation of molecular assemble via tuning alkyl side‐chain topology in a series of low‐cost nonfused‐ring electron acceptors (NFREAs). Among the three NFREAs investigated, DPA‐4, which possesses an asymmetric alkyl side‐chain length, exhibits a tight packing in the crystal and high crystallinity in the film, contributing to improved electron mobility and favorable film morphology for DPA‐4. As a result, the OSC device based on DPA‐4 achieves an excellent power conversion efficiency of 16.67 %, ranking among the highest efficiencies for NFREA‐based OSCs. [ABSTRACT FROM AUTHOR]

A pyrene‐fused dimerized electron acceptor has been successfully synthesized and subsequently incorporated as the third component in ternary organic solar cells (OSCs). Diverging from the traditional dimerized acceptors with a linear configuration, this novel electron acceptor displays a distinctive "butterfly‐like" structure, comprising two Y‐acceptors as wings fused with a pyrene‐based backbone. The extended π‐conjugated backbone and the electron‐donating nature of pyrene enable the new acceptor to show low solubility, elevated glass transition temperature (Tg), and low‐lying frontier energy levels. Consequently, the new dimerized acceptor seamlessly integrates as the third component into ternary OSCs, enhancing electron transporting properties, reducing non‐radiative voltage loss, and elevating open‐circuit voltage. These merits have enabled the ternary OSCs to show an exceptional efficiency of 19.07%, a marked improvement compared to the 17.6% attained in binary OSCs. More importantly, the high Tg exhibited by the pyrene‐fused electron acceptor helps to stabilize the morphology of the photoactive layer thermal‐treated at 70 °C, retaining 88.7% efficiency over 600 hours. For comparison, binary OSCs experience a decline to 73.7% efficiency after the same duration. These results indicate that the "butterfly‐like" design and the incorporation of a pyrene unit is a promising strategy in the development of dimerized electron acceptors for OSCs. [ABSTRACT FROM AUTHOR]

Comprehensive Summary: By simplifying the π‐bridge unit, a nonfused ring electron acceptor (NFREA) BM‐2F was designed and synthesized with several high‐yield steps. The specific molecular structure features of BM‐2F are planar molecular backbone and out‐of‐plane side chain, which is favorable for charge transport and can suppress the over‐aggregation. BM‐2F based neat and blend films display obvious face‐on molecular orientation. Specially, D18:BM‐2F based blend film can form good bicontinuous interpenetrating network. More excitingly, a power conversion efficiency of 16.15% was achieved with D18:BM‐2F based photovoltaic devices, which is the highest one based on NFREAs. Our researches manifest that NFREA is a promising direction for low‐cost and high‐performance organic solar cells. [ABSTRACT FROM AUTHOR]

Double‐cable conjugated polymers with near‐infrared (NIR) electron acceptors are synthesized for use in single‐component organic solar cells (SCOSCs). Through the development of a judicious synthetic pathway, the highly sensitive nature of the 2‐(3‐oxo‐2,3‐dihydroinden‐1‐ylidene)malononitrile (IC)‐based electron acceptors in basic and protonic solvents is overcome. In addition, an asymmetric design motif is adopted to optimize the packing of donor and acceptor segments, enhancing charge separation efficiency. As such, the new double‐cable polymers are successfully applied in SCOSCs, providing an efficiency of over 10 % with a broad photo response from 300 to 850 nm and exhibiting excellent thermal/light stability. These results demonstrate the powerful design of NIR‐acceptor‐based double‐cable polymers and will enable SCOSCs to enter a new stage. [ABSTRACT FROM AUTHOR]

The rapid advance of fused‐ring electron acceptors (FREAs) has greatly promoted the leap‐forward development of organic solar cells (OSCs). However, the synthetic complexity of FREAs may be detrimental for future commercial applications. Recently, nonfused‐ring electron acceptors (NREAs) have been developed to be a promising candidate to maintain a rational balance between cost and performance, of which the cores are composed of simple fused rings (NREAs‐I) or nonfused rings (NREAs‐II). Moreover, "noncovalently conformational locks", are used as an effective strategy to enhance the rigidity and planarity of NREAs and improve device performance. Herein, a novel series of NREAs‐II (PhO4T‐1, PhO4T‐2, and PhO4T‐3) is constructed as a valuable platform for exploring the impact of the end group engineering on optoelectronic properties, intermolecular packing behaviors, and device performance. As a result, a high power conversion efficiency of 13.76% is achieved for PhO4T‐3 based OSCs, which is much higher than those of the PhO4T‐1 and PhO4T‐2‐based devices. Compared with several representative FREAs, PhO4T‐3 possesses the highest figure‐of‐merit value of 133.45 based on a cost‐efficiency evaluation. This work demonstrates that the simple‐structured NREAs‐II are promising candidates for low‐cost and high‐performance OSCs. [ABSTRACT FROM AUTHOR]

Three nonfused ring electron acceptors (NFREAs; 2Th‐2F, BTh‐Th‐2F, and 2BTh‐2F) with thieno[3,2‐b]thiophene bearing two bis(4‐butylphenyl)amino substituents as the core, 3‐octylthiophene or 3‐octylthieno[3,2‐b]thiophene as the spacer, and 3‐(1,1‐dicyanomethylene)‐5,6‐difluoro‐1‐indanone as the terminal group are designed and synthesized. The molar extinction coefficient of acceptors and the electron mobility of blend films gradually increase with increasing π‐conjugation length. Moreover, 2BTh‐2F displays a planar molecular conformation assisted by S···N and S···O intramolecular interactions. More importantly, the molecular stacking changes from 2D packing for the 2Th‐2F analog to 3D network packing for 2BTh‐2F. Due to these comprehensive merits, 2BTh‐2F:PBDB‐T‐based organic solar cells give a high power conversion efficiency of 14.53%. More impressively, when D18 is used as the donor polymer, the power conversion efficiency is further enhanced to 15.44%, which is the highest value reported for solar cells based on NFREAs. [ABSTRACT FROM AUTHOR]

We developed a series of highly crystalline double‐cable conjugated polymers for application in single‐component organic solar cells (SCOSCs). These polymers contain conjugated backbones as electron donor and pendant perylene bisimide units (PBIs) as electron acceptor. PBIs are connected to the backbone via alkyl units varying from hexyl (C6H12) to eicosyl (C20H40) as flexible linkers. For double‐cable polymers with short linkers, the PBIs tend to stack in a head‐to‐head fashion, resulting in large d‐spacings (e.g. 64 Å for the polymer P12 with C12H24 linker) along the lamellar stacking direction. When the length of the linker groups is longer than a certain length, the PBIs instead adopt a more ordered packing likely via H‐aggregation, resulting in short d‐spacings (e.g. 50 Å for the polymer P16 with C16H32 linker). This work highlights the importance of linker length on the molecular packing of the acceptor units and the influences on the photovoltaic performance of SCOSCs. [ABSTRACT FROM AUTHOR]

Isomeric effects play a crucial role in regulating electronic properties, molecular packing, and device performance of organic semiconductors. Herein, a series of unfused‐ring electron acceptor (UREA) regioisomers (NOF‐1, NOF‐2, and NOF‐3), which are constructed using 2,6‐α‐, 1,5‐β‐, and 3,7‐β‐type naphthalene cores, are successfully synthesized and characterized. The regioisomeric effects on geometries, photophysics, electrical properties, molecular packing behaviors, charge transport properties, blend film morphologies, and photovoltaic performance are systematically studied. As a result, the PBDB‐T:NOF‐3‐based device delivers a power conversion efficiency (PCE) of 11.58% due to its more balanced charge mobility, efficient exciton dissociation, less charge recombination, and favorable film morphology. These findings encourage further attention to the regioisomeric effects to design high‐performance UREAs. [ABSTRACT FROM AUTHOR]

Fused‐ring electron acceptors have made significant progress in recent years, while the development of fully non‐fused ring acceptors has been unsatisfactory. Here, two fully non‐fused ring acceptors, o‐4TBC‐2F and m‐4TBC‐2F, were designed and synthesized. By regulating the location of the hexyloxy chains, o‐4TBC‐2F formed planar backbones, while m‐4TBC‐2F displayed a twisted backbone. Additionally, the o‐4TBC‐2F film showed a markedly red‐shifted absorption after thermal annealing, which indicated the formation of J‐aggregates. For fabrication of organic solar cells (OSCs), PBDB‐T was used as a donor and blended with the two acceptors. The o‐4TBC‐2F‐based blend films displayed higher charge mobilities, lower energy loss and a higher power conversion efficiency (PCE). The optimized devices based on o‐4TBC‐2F gave a PCE of 10.26 %, which was much higher than those based on m‐4TBC‐2F at 2.63 %, and it is one of the highest reported PCE values for fully non‐fused ring electron acceptors. [ABSTRACT FROM AUTHOR]

Comprehensive Summary: By simplifying the π‐bridge unit, a nonfused ring electron acceptor (NFREA) BM‐2F was designed and synthesized with several high‐yield steps. The specific molecular structure features of BM‐2F are planar molecular backbone and out‐of‐plane side chain, which is favorable for charge transport and can suppress the over‐aggregation. BM‐2F based neat and blend films display obvious face‐on molecular orientation. Specially, D18:BM‐2F based blend film can form good bicontinuous interpenetrating network. More excitingly, a power conversion efficiency of 16.15% was achieved with D18:BM‐2F based photovoltaic devices, which is the highest one based on NFREAs. Our researches manifest that NFREA is a promising direction for low‐cost and high‐performance organic solar cells. [ABSTRACT FROM AUTHOR]

A new nonfused ring electron acceptor PDI-DO-2F is designed and synthesized by attaching perylenediimide (PDI) unit as a pendent group to the central donor core. Compared with the control molecule DO-2F , the introduction of PDI lateral substituent can greatly enhance the solubility and decrease the crystallinity of the resulted acceptor. The PBDB-T :PDI-DO-2F blend film exhibits a much better morphology with higher and more balanced carrier mobility in contrast to PBDB-T :DO-2F one. PDI-DO-2F based organic solar cells (OSCs) give a power conversion efficiency (PCE) of 11.78%, higher than DO-2F based ones (9.82%). Furthermore, PDI-DO-2F based OSCs shows a Δ E non-rad value of 0.23 eV, which is significantly lower than the DO-2F based ones (0.28 eV). More importantly, the addition of PDI-DO-2F as the third component to the PBDB-T :DO-2F binary system can optimize the morphology of blend films and improve the shelf stability of devices. And the PBDB-T :DO-2F : PDI-DO-2F based ternary OSCs achieve a higher PCE of 13.82%. [Display omitted] • A new nonfused ring electron acceptor is designed and synthesized. • PDI unit as a pendent group can greatly enhance the solubility and decrease the crystallinity of the acceptor. • Significantly different power conversion efficiencies of 9.82%, 11.78% and 13.82% are achieved. [ABSTRACT FROM AUTHOR]

[Display omitted] • We can modularly synthesize two fully nonfused ring acceptors with only four high-yield steps. • A simple fully nonfused ring electron acceptor can achieve a high PCE of over 12%. • The high FOM of 4T-OEH indicates its great potential for future practical applications. We designed two simple fully nonfused ring electron acceptors 4T-OEH and 4T-EH with 3,4-bis(alkoxy)thiophene and 3,4-dialkylthiophene π-bridge units, respectively, which can be modularly synthesized with only four high-yield steps. With the help of intramolecular S-O noncovalent interaction, 4T-OEH tends to form a planar molecular backbone, which is beneficial for the electron delocalization and charge transport. Besides, the neat 4T-OEH film displays a more ordered molecular packing and obviously red-shifted absorption after thermal annealing. Compared with 4T-EH , 4T-OEH based devices can form more homogenous phase morphology, higher and more balanced hole and electron mobilities. The optimal OSCs based on 4T-OEH can generate an excellent PCE of 12.12%, which is much higher than 4T-OEH based ones (7.36%). It is worth noting that the figure-of-merit values of 4T-OEH is much higher than the star acceptors (ITIC and Y6), demonstrating its high potential for future practical application. Our work has demonstrated that we can tune the backbone planarity, solubility and packing behavior of acceptor molecules via optimizing their lateral substituents to obtain high efficiency and low-cost fully nonfused ring electron acceptors. [ABSTRACT FROM AUTHOR]

• Minor terminal and central changes endow DO-2F and FO-N complementary absorption. • Asymmetrical FO-N effectively suppress the self-aggregation of DO-2F. • Acceptor alloy is found between the FO-N and DO-2F. • Alloy state acceptors produce suitable morphology with reduced V nr of 0.23 eV. • FO-N is an excellent third component for highly efficient OSCs of 14.10% Nonfused ring acceptors have shown great potential for future commercial applications of organic solar cells (OSCs) due to their simple structure and low synthetic costs. Herein, a novel asymmetrical nonfused ring acceptor FO-N with one branched lateral chain and one fluoro substituent at the central phenylene core was designed and introduced into PBDB-T : DO-2F binary system to fabricate high-efficiency ternary OSCs. The high-lying LUMO level of FO-N is conducive to improve V oc for ternary devices. More importantly, the introduction of FO-N as the third component can efficiently improve the compatibility of the ternary system via tuning the crystal size and optimizing the blend film morphology, which is beneficial to charge separation and reduced the non-radiative energy loss (Δ E nonrad). Finally, the ternary device achieved a low Δ E nonrad of 0.23 eV and a greatly improved PCE of 14.10% and with a V oc of 0.88 V, a J sc of 21.48 mA/cm2 and an FF of 74.41%. These results imply that the asymmetric nonfused ring acceptor design strategy is an effective way for optimizing the photovoltaic performance of highly crystallized blend system. [ABSTRACT FROM AUTHOR]

[Display omitted] • Two isomeric fully nonfused ring electron acceptors are designed and synthesized. • The location of diphenylamine units can adjust the properties of acceptors. • Significantly different power conversion efficiencies of 12.83% and 0.43% are achieved. We have designed and synthesized two fully nonfused ring electron acceptors LW-in-2F and LW-out-2F with two diphenylamine side chains at different positions of the bithiophene core. The two diphenylamine side chains of LW-in-2F and LW-out-2F are at the outside and inside positions of the central bithiophene unit, respectively. The performance of LW-in-2F and LW-out-2F -based devices is very different, the photoelectric conversion efficiency (PCE) of LW-out-2F -based device is as high as 12.83%, while the efficiency of LW-in-2F -based device is only 0.43%. By GIWAXS test, we found that the change of diphenylamine position affects the way of molecular arrangement. When the diphenylamine side chain is located on the outer side of the central core, the molecular arrangement shows face-on orientation, which is beneficial for perpendicular charge transport, resulting in high and balanced charge mobilities and high PCE. [ABSTRACT FROM AUTHOR]