Nonfullerene organic solar cells (NFOSCs) are attracting increasing academic and industrial interest due to their potential uses for flexible and lightweight products using low‐cost roll‐to‐roll technology. In this work, two wide bandgap (WBG) polymers, namely P(fTh‐BDT)‐C6 and P(fTh‐2DBDT)‐C6, are designed and synthesized using benzodithiophene (BDT) derivatives. Good oxidation stability and high solubility are achieved by simultaneously introducing fluorine and alkyl chains to a single thiophene (Th) unit. Solid P(fTh‐2DBDT)‐C6 films present WBG optical absorption, suitable frontier orbital levels, and strong π–π stacking effects. In addition, P(fTh‐2DBDT)‐C6 exhibits good solubility in both halogenated and nonhalogenated solvents, suggesting its suitability as donor polymer for NFOSCs. The P(fTh‐2DBDT)‐C6:3,9‐bis(2‐methylene‐(3‐(1,1‐dicyanomethylene)‐indanone))‐5,5,11,11‐tetrakis(5‐hexylthienyl)‐dithieno[2,3‐d:2′,3′‐d′]‐s‐indaceno[1,2‐b:5,6‐b′]dithiophene (ITIC‐Th) based device processed using chlorobenzene/1,8‐diiodooctane (CB/DIO) exhibits a remarkably high power conversion efficiency (PCE) of 11.1%. Moreover, P(fTh‐2DBDT)‐C6:ITIC‐Th reaches a high PCE of 10.9% when processed using eco‐friendly solvents, such as o‐xylene/diphenyl ether (DPE). The cell processed using CB/DIO maintains 100% efficiency after 1272 h, while that processed using o‐xylene/DPE presents a 101% increase in efficiency after 768 h and excellent long‐term stability. The results of this study demonstrate that simultaneous fluorination and alkylation are effective methods for designing donor polymers appropriate for high‐performance NFOSCs.

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OSCs can be applied to various fields due to their many advantages, such as high performance, low cost, flexibility, and potential for modulation. Recently, the research on OSCs has been focused on materials with high-performance organic donors and acceptors (fullerene and nonfullerene) and device structure research, such as ternary structure and tandem structure. These studies have contributed to developing high-performance OSCs with excellent power conversion efficiency (PCE) over 14% in single cells and 17.3% in tandem structure cells. [1][2][3][4][5][6][7][8][9][10] OSCs are based on an active layer that has a bulk-heterojunction (BHJ) structure that consists of an organic donor and acceptor, and OSCs generate excitons within the range of their optical properties. Additionally, OSCs show photovoltaic properties via the process of charge disassociation and charge transport. [11,12] Due to the limitation of the optical properties of organic donors and acceptors, carrier mobility and carrier balance are critical factors that determine the performance of OSCs. [13][14][15][16] Therefore, photogenerated carriers that have been generated in a BHJ have the disadvantage of exhibiting a lower mobility compared with inorganic semiconductor-based solar cells because of the organic semiconductor's inherent properties, such as monomolecular recombination and bimolecular recombination. [17][18][19] Additionally, certain of these photogenerated carriers return to the ground state through monomolecular trap-assisted recombination, [20][21][22] interfacial recombination, [23][24][25] and surface trap-assisted recombination, [26] and the carriers subsequently weaken the device performance because the reduction of current and internal potential occurs via a nonradiative relaxation process. [27,28] Therefore, it is necessary to enhance the carrier transport properties to improve the performance of OSCs.Recent research has reported important device structure modifications to improve the carrier transport properties of OSCs. Specifically, the carrier mobility can be increased by introducing a buffer layer through enhancing carrier transport, and the device performance can be enhanced by reducing the recombination. Hybrid organic solar cells are made through a simple one-pot coating process with conjugated polyelectrolytes (CPEs), poly[9,9-bis(4′sulfonatobutyl)fluorenealt-thiophene-doped (PFT-D). The hybrid active layer incorporated with PFT-D shows vertical phase separation by selfassembled properties of PFT-D, which result from a molecular dipole between the conjugated backbone and the side chain. The hybrid activelayer with PFT-D shows that homogeneous morphology, surface potential properties, and hydrophobic surface properties favor for enhancing photovoltaic performance. These results are identified by contact angle characteristics, X-ray photoelectron spectroscopy (XPS) profiling, and X-ray diffraction (XRD), atomic force measurement (AFM), and electrostatic force measurement (EFM) analyses. With fullerene based hybrid active...

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