Binary Blend All‐Polymer Solar Cells with a Record Efficiency of 17.41% Enabled by Programmed Fluorination Both on Donor and Acceptor Blocks

Abstract

Despite remarkable breakthrough made by virtue of “polymerized small‐molecule acceptor (PSMA)” strategy recently, the limited selection pool of high‐performance polymer acceptors and long‐standing challenge in morphology control impede their further developments. Herein, three PSMAs of PYDT‐2F, PYDT‐3F, and PYDT‐4F are developed by introducing different fluorine atoms on the end groups and/or bithiophene spacers to fine‐tune their optoelectronic properties for high‐performance PSMAs. The PSMAs exhibit narrow bandgap and energy levels that match well with PM6 donor. The fluorination promotes the crystallization of the polymer chain for enhanced electron mobility, which is further improved by following n ‐doping with benzyl viologen additive. Moreover, the miscibility is also improved by introducing more fluorine atoms, which promotes the intermixing with PM6 donor. Among them, PYDT‐3F exhibits well‐balanced high crystallinity and miscibility with PM6 donor; thus, the layer‐by‐layer processed PM6/PYDT‐3F film obtains an optimal nanofibril morphology with submicron length and ≈23 nm width of fibrils, facilitating the charge separation and transport. The resulting PM6/PYDT‐3F devices realizes a record high power conversion efficiency (PCE) of 17.41% and fill factor of 77.01%, higher than the PM6/PYDT‐2F (PCE = 16.25%) and PM6/PYDT‐4F (PCE = 16.77%) devices.

Y-Series-Based Polymer Acceptors for High-Performance All-Polymer Solar Cells in Binary and Non-binary Systems

“…Another design strategy involves the halogenation on both the core and linker moieties. Peng et al demonstrated three Y-series-based polymer acceptors, PYDT-2F, PYDT-3F, and PYDT-4F, with varying numbers of fluorine atoms on the end groups and bithiophene linkers . With the increasing of the number of fluorine substituent, narrow optical band gap, down-shifted HOMO level, reduced surface energy, and enhanced miscibility with the fluorinated donor polymer PM6 could be achieved.…”

“…Peng et al demonstrated three Yseries-based polymer acceptors, PYDT-2F, PYDT-3F, and PYDT-4F, with varying numbers of fluorine atoms on the end groups and bithiophene linkers. 83 With the increasing of the number of fluorine substituent, narrow optical band gap, down-shifted HOMO level, reduced surface energy, and enhanced miscibility with the fluorinated donor polymer PM6 could be achieved. Especially, all-PSC based on PM6:PYDT-3F exhibited a maximum PCE of 17.41% with a high FF of 77.01% owing to the deep HOMO level of PM6 and the favorable morphology of the blend film.To create advanced Y-series-based polymer acceptors with excellent power conversion efficiency values of binary and non-binary all-polymer solar cells, a simultaneous investigation must be conducted on the Y-series-based small-molecule acceptors and linkers.…”

Tuning the Crystallinity and Phase Separation by Two‐Step Annealing Enables Block Copolymer‐Based Organic Solar Cells with 15% Efficiency

“…In view of this, all-polymer based systems have been paid large efforts to by the field, as their stability should be intrinsically higher than those with small molecules, and the efficiency of these types of solar cells has also reached a decent level of 16%. [12][13][14][15][16][17][18][19][20][21] At the same time, different from the binary all-polymer blend with polymer donor and polymer acceptor, the one-pot-synthesized block copolymer systems are also considered a rising star for pursing the balance of efficiency and stability. [22][23][24][25] Accordingly, the prospect of promoting the efficiency of block copolymer-based OSCs could be bright, as its units are chemically bonded together, which would be beneficial to resisting the morphology degradation.…”

Highly efficient and stable binary all-polymer solar cells enabled by sequential deposition processing tuned microstructures

“…Though this gap has been successfully alleviated by the new concept of a polymerized small molecular acceptor (PSMA), specifically PCEs are now over 16% in multiple cases. [21][22][23][24][25][26][27][28][29] Nonetheless, the operational and mechanical stability difficulties come back again, due to PSMAs partially inheriting the properties of small molecules. [30][31][32][33] Since current PSMA-type materials are the most promising candidates for high-efficiency, more efforts in boosting device stability are required that rely not only on chemistry innovation, but also effective device fabrication methods.…”