Recent Research Progress of n-Type Conjugated Polymer Acceptors and All-Polymer Solar Cells

Non‐Fully Conjugated Photovoltaic Materials with Y‐Series Acceptor Backbone for High‐Performance Organic Solar Cells†

“…However, before 2017, compared to the diversity of SMAs (especially the A‐D‐A‐typed SMAs with small E g opt , high extinction coefficient, and adjustable energy levels, such as ITIC and its derivatives, developed by Zhan et al . ), [ 45 ] polymer acceptors are structurally limited to such few units as fused‐ring diimide (such as naphthalene diimide/NDI, [ 46 ] perylene diimide/PDI, [47 and multi‐thiophene‐ fused diimide/ThDI [ 48 ] ) and B→N‐bridged bipyridine building blocks [ 49 ] with some clear shortcomings of low absorption coefficient of ~10 4 cm –1 and/or narrow absorption spectra of 300—700 nm, leading to far from satisfactory PCEs. To solve the above‐ mentioned shortcomings, in 2017, Li et al .…”

“…[ 44‐45 ] Thanks to the unique DA’D‐fused twisted core and 3D intermolecular packing and charge transport of Y‐series precursor SMAs, theses polymer acceptors provide excellent photovoltaic performance with both high V OC , J SC , and FF due to their E loss , NIR‐absorption, and high carrier mobility. [ 46 ] Recently, a great number of high‐performance PSMAs have been developed by polymerizing Y‐series SMAs with various linkers (such as thiophene, selenophene, benzodithiophene, dithiophene, thienothiophene, thiophene‐vinylene‐thiophene, bithiophene‐fused imide, etc .). [ 15‐18,50‐52 ] As a result, significant improvement in device performance has been achieved in all‐PSCs, with the state‐of‐the‐art of PCEs exceeding 19%.…”

Modulating the Central Units of Polymerized Nonfused Electron Acceptors for All-Polymer Solar Cells

“…In 2017, polymerized small-molecule acceptors (PSMAs) were applied to all-PSCs by Li’s group . This novel acceptor combines the advantages of small molecules and polymers, including high absorption coefficients with broad photoresponse, high electron mobilities, and well-aligned energy levels. , The flexibility in the structural design of PSMAs gradually clarified the structure–property relationships in all-PSCs. − Thanks to the high-performance module molecule Y6, the PCEs of all-PSCs based on PSMAs exceeded 17%. , However, molecules with fused-ring structures are generally more complex to synthesize, thereby increasing the synthesis cost. PSMAs based on nonfused-core structures have gradually gained attention because of their advantages of simple synthesis and considerable performance. − Nevertheless, most researches of nonfused-core-based PSMAs focus on the adjustment of the end groups and comonomers. ,,,− The influence of modulating the central units on the photophysical properties of nonfused-core-based PSMAs has not yet been studied.…”

“…25 This novel acceptor combines the advantages of small molecules and polymers, including high absorption coefficients with broad photoresponse, high electron mobilities, and well-aligned energy levels. 26,27 The flexibility in the structural design of PSMAs gradually clarified the structure−property relationships in all-PSCs. 28−38 Thanks to the high-performance module molecule Y6, the PCEs of all-PSCs based on PSMAs exceeded 17%.…”

Precise synthesis and photovoltaic properties of giant molecule acceptors

“…However, the early polymer acceptors used in all-PSCs exhibited weak absorbance in the near-infrared region and unsuitable molecular packing 6 , 7 , which limited the further development of all-PSCs. To address these issues and increase the power conversion efficiency (PCE) of all-PSCs, Zhang and Li et al 8 proposed the concept of polymerizing small molecule acceptor (PSMA) to construct the emerging generation polymer acceptors with the narrow bandgap small molecule acceptors (SMAs) as the key building blocks 9 , 10 . The PSMAs possess the advantages of its SMA building blocks with low bandgap, strong absorption in the near-infrared region, suitable molecular packing and smaller exciton binding energy than the SMA building block, which prompt the PCE of the all-PSCs to over 17% recently 11 – 14 .…”