Although ternary organic solar cells (OSCs) have unique advantages in improving device performance, the morphology assembly in the ternary‐phase would be more uncertain or complex than that in the binary‐phase. Here, we propose a new concept of oligomer‐assisted photoactive layers for high‐performance OSCs. The formed alloy‐like phase of the oligomer : host polymer blend enabled the oligomer‐assisted OSCs to fuse the advantages of both binary and ternary devices, exhibiting substantially enhanced performance and stability compared to the control devices. With the addition of oligomers, outstanding efficiencies of 17.33 % for a PM6 : Y6 device, 18.32 % for a PM6 : BTP‐eC9 device, and 17.13 % for a PM6/Y6 pseudo‐bilayer device were achieved, all of which are one of the highest values in their corresponding fields. The improved performance originated from the downshift energy levels, enhanced light absorption, optimized blend morphology, favorable charge dynamics, and reduced non‐radiative energy loss.

Semitransparent organic solar cells (ST‐OSCs) based on all narrow bandgap (all‐NBG) semiconductors are attractive for building integration. Unfortunately, advanced NBG Y‐series acceptors cannot well match with the NBG donors, resulting from their mismatched energy levels and poor compatibility. Herein, a facile terpolymer design strategy is adopted to improve the matching of Y6 with efficient NBG polymer donor PCE10. F or Cl atom functionalized benzodithiophene (BDT) are introduced into the PCE10 matrix to afford two series of terpolymers, namely PCE10‐BDT2F and PCE10‐BDT2Cl. Compared with PCE10, all terpolymers show deeper energy levels, higher extinction coefficients, enhanced face‐on orientation, and better compatibility with Y6. Consequently, significant breakthroughs are achieved for both opaque and semitransparent devices. Particularly, a record power conversion efficiency (PCE) of 13.80% is achieved by PCE10‐BDT2F:Y6‐based device, nearly 40% higher than PCE10:Y6‐based device. ST‐OSCs also achieve impressive PCEs of 12.00% and 10.85% with average visible transmittance (AVT) of 30.98% and 41.08%, respectively, and both PCEs are the highest values with AVT over 30% and 40%. An outstanding light utilization efficiency (LUE) of 4.46% further demonstrates the successful balance of PCE and AVT. These results demonstrate that the design of NBG terpolymers is a facile and highly encouraging strategy for promoting breakthroughs in ST‐OSCs.

Organic semiconductor (OSCs) thermoelectric materials have been studied widely due to their low thermal conductivity and solution processing characteristics. Currently, the high conductivity (up to 1000 s cm−1) has boosted the performance of p‐type organic thermoelectric materials substantially. In contrast, the development of n‐type organic thermoelectric materials is still limited by their low mobility, inferior air stability, and poor doping efficiency, which is relevant to the molecule structure and dopant dispersion. Herein, the recent development of n‐type organic thermoelectric materials was reviewed with an emphasis on molecule structure modification and solution processing. Methods for optimizing conjugate structure were summarized from the effects of conjugated backbone modification and side chains diversification on molecular stacking. The primary n‐type dopants were also summarized briefly. Especially, the role of solution aggregation controlling on film preparation and properties was given special attention. Additionally, the emergence of organic diradicals with low lowest unoccupied molecular orbital energy level and no doping was introduced, which shows great potential in n‐type organic thermoelectric materials. All these endeavors have led to the development of n‐type OSCs materials. This Review is aimed at illustrating the state‐of‐the‐art progress and providing some guideline for the design of organic thermoelectric materials in the future.

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Unfused-ring acceptors (UFAs) show bright application prospects in organic solar cells (OSCs) thanks to their easy synthesis, low cost, and good device performance. The selection of central-core building block and suitable side chain are the key factors to achieve high-performance UFAs. Current tremendous endeavors for the development of UFAs mainly concentrate on obtaining higher short-circuit current density (J sc ), albeit accompanied by low open-circuit voltage (V oc ) and modest fill factor (FF). Herein, two novel AÀ DÀ A'À DÀ A type UFAs (BTCD-IC and BTCD-2FIC), which have the same new electron-withdrawing central-core dithieno [3',2':3,4;2'',3'':5,6]-benzo[1,2c][1,2,5]thiadia-zole (DTBT) and cyclopentadithiophene unit (CPDT, substituted by 2-butyl-1-octyl alkyl chain) coupling with different terminals, were designed and synthesized. Two UFAs showed strong and broad light absorption in the wavelength range of 300-850 nm owing to the strong intramolecular charge transfer effect favorable by DTBT core. Compared with BTCD-IC, BTCD-2FIC with F-containing terminal group exhibited higher molar extinction coefficient, lower energy level, higher charge mobility, stronger crystallinity, more ordered molecular stacking, and better film morphology. As a result, when blended with donor polymer PBDB-T (poly [(2,6-(4,8-bis(5-(2-ethylhexyl)), the BTCD-2FIC-based OSC achieved a superior power conversion efficiency (PCE) of 11.32 %, with a high V oc of 0.85 V, a J sc of 18.24 mA cm À 2 , and a FF of 73 %, than BTCD-IC-based OSC (PCE = 8.96 %). Impressively, the simultaneously enhanced V oc and FF values of the PBDB-T:BTCD-2FIC device were the highest values of the AÀ DÀ A'À DÀ A-type UFAs. The results demonstrate the application of electron-withdrawing DTBT central-core unit in efficient UFAs provides meaningful molecular design guidance for high-performance OSCs.

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Although breakthroughs have been made in organic solar cells (OSCs) in recent years, the power conversion efficiency (PCE) of OSCs still lags behind inorganic/perovskite solar cells. In this work, two terpolymers were synthesized by introducing the thieno[3,4‐c]pyrrole‐4,6‐(5H)‐dione (TPD) block into the host polymer donor PM6. Owing to the lower highest occupied molecular orbital energy level, wider light absorption, optimal molecular packing, and more desirable aggregation morphology by addition of the TPD, the PM6‐TPD‐5 % : Y6‐based device displayed an improved PCE of 16.3 % with an enhanced open‐circuit voltage (VOC) of 0.860 V, relative to that of PM6‐TPD‐10 % : Y6 (PCE=14.8 %) and PM6 : Y6‐based device (PCE=15.6 %). Interestingly, the VOC did not always increase in proportion to the third component. Besides, ternary OSCs based on PM6 : PM6‐TPD‐5 % : Y6 achieved a superior PCE of 17.1 %. This work demonstrated that random copolymerization is a feasible and effective strategy to further increase device performance, and the two polymers that possess similar structure and absorption in ternary devices can also obtain impressive efficiency.

Poor miscibility between the polymer donor and acceptor in the active layer leads to low fill factors (FF). PCl and PCl‐Si are synthesized by polymerization of the accessible and inexpensive IDIC‐C16 with BDT‐Cl and BDT‐Cl‐Si, respectively. PCl and PCl‐Si involve a BDT skeleton that is definitely used in most highly efficient polymer donors, such as PM6. Guided by the law of similarity and intermiscibility, the similar building block acts as a bridge to improve the interfacial interaction and miscibility between the donor and acceptor, leading to a favorable morphology of the active layer. It is found that the miscibility of the active layer is sensitive to the structural similarity degree of the similar unit of the donor and acceptor. The PCl‐Si‐based device delivers a power conversion efficiency (PCE) of 9.25% with a moderate FF of 67.86%, whereas the PM6:PCl‐based device achieves a PCE of 10.02% with a higher FF of 70.25%, which is the highest FF of the device with an IDIC‐C16‐based polymer acceptor. In addition, the improved interaction between the donor and acceptor improves the device stability. These results demonstrate that regulating the structural similarity between donor and acceptor is a promising strategy to optimize and stabilize morphology for high‐performance all‐polymer solar cells.