With the emergence of ADA'DA-type (Y-series) non-fullerene acceptors (NFAs), the power conversion efficiencies (PCEs) of organic photovoltaic devices have been constantly refreshed and gradually reached 20% in recent years (19% for single junction and 20% for tandem device). The acceptors possess specific design concept, which greatly enrich the NFA types and have excellent compatibility with many donor materials. It is gratifying to note that the previously underperforming donor materials combine with these regulated acceptors to shine again. Nowadays, the concept of modular design is widely used in the research of acceptors and donors, injecting new vitality into the field of organic photovoltaics. Furthermore, these acceptors also promote the research of multicomponent devices, tandem devices, bilayer devices, processing solvent engineering, and additive engineering. Herein, the latest progresses of polymer solar cells with efficiency over 17% are briefly reviewed from the aspects of active material design, interface material development, and device technology. At last, the opportunities and challenges of organic photovoltaic commercialization in the future are discussed.

Voltage loss is an inescapable problem in ternary polymer solar cells (PSCs) because of utilizing photovoltaic materials with complementary absorption. In this work, two donor structure (D1:D2:A) ternary PSCs comprising a poly­[(2,6-(4,8-bis­(5-(2-hexyldecyl-3-fluoro)­thiophen-2-yl)-benzo­[1,2-b:4,5-b′]­dithiophene))-alt-(5,5-(2,6-di-2-thienyl)-4,8-bis­(5-(2-hexyldecyl)­thiophen-2-yl)­benzo­[1,2-d:4,5-d′]­bis­(thiazole))] (PBB-F), poly­[(2,6-(4,8-bis­(5-(2-ethylhexyl-3-fleoro)­thiophen-2-yl)-benzo­[1,2-b:4,5-b′]­dithiophene))-alt-(5,5-(1′,3′-di-2-thienyl-5′,7′-bis­(2-ethylhexyl)­benzo­[1′,2′-c:4′,5′-c′]­dithiophene-4,8-dione)] (PM6), and 3,9-bis­(2-methylene-((3-(1,1-dicyanomethylene)-6,7-difluoro)-indanone))-5,5,11,11-tetrakis­(4-hexylphenyl)-dithieno­[2,3-d:2′,3′-d′]-s-indaceno­[1,2-b:5,6-b′]­dithiophene) (IT-4F) system exhibit low voltage loss with no cascade energy level structure, whereas the corresponding devices acquire enhanced power conversion efficiency (PCE) of 15.08%. The increased PCEs are ascribed to the improved phase separation after incorporating PM6, and thus, the charge recombination loss can be suppressed and the charge transport and extraction can be enhanced. Importantly, Kelvin probe force microscopy (KPFM) of two donor material blend films on poly­(3,4-ethylenedioxythiophene):poly­(styrenesulfonate) (PEDOT:PSS) or ZnO (under dark and 638 nm irradiation conditions) is performed to check the exciton separation dynamics of photovoltaic materials, and the results intuitively demonstrated that holes can efficiently transfer from the high highest occupied molecular orbital (HOMO) of donor PM6 to the low HOMO of donor PBB-F, which ensures unblocked hole transport channels and thus induces low voltage loss. Besides, the D1:D2:A PSCs showed broad component tolerance from 10 to 50% blend ratios for PM6, which is conducive to large-scale commercialization fabrication conditions.

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