A Difluoro‐Monobromo End Group Enables High‐Performance Polymer Acceptor and Efficient All‐Polymer Solar Cells Processable with Green Solvent under Ambient Condition

Abstract

In this paper, a difluoro-monobromo end group is designed and synthesized, which is then used to construct a novel polymer acceptor (named PY2F-T) yielding high-performance all-polymer solar cells with 15.22% efficiency. The fluorination strategy can increase the intramolecular charge transfer and interchain packing of the previous PY-T based acceptor, and significantly improve photon harvesting and charge mobility of the resulting polymer acceptor. In addition, detailed morphology investigations reveal that the PY2F-T-based blend shows smaller domain spacing and higher domain purity, which significantly suppress charge recombination as supported by time-resolved techniques. These polymer properties enable simultaneously enhanced J SC and FF of the PY2F-T-based devices, eventually delivering device efficiencies of over 15%, significantly outperforming that of the devices based on the non-fluorinated PY-T polymer (13%). More importantly, the PY2F-T-based active layers can be processed under ambient conditions and still achieve a 14.37% efficiency. They can also be processed using non-halogenated solvent o-xylene (no additive) and yield a decent performance of 13.05%. This work demonstrates the success of the fluorination strategy in the design of high-performance polymer acceptors, which provide guidelines for developing new all-PSCs with better efficiencies and stabilities for commercial applications.

Polymerizing small molecular acceptors for efficient all‐polymer solar cells

“…Most recently, He et al 26 reported the same strategy of configurational control with isolated IC‐Br‐γ and IC‐Br‐δ on a large scale to design new polymer acceptors, and successfully produced two regioregular narrow‐bandgap PSMAs, PBTIC‐γ‐2F2T and PBTIC‐δ‐2F2T. Their study also highlighted that precise control of the molecular configuration enhanced the charge carrier mobility and decreased the π ‐ π stacking distance, which afforded higher performance in all‐PSCs 28,32,33 . Additionally, Liu et al 32 obtained an optimal morphology, reduced nonradiative energy loss, and an impressive PCE of 16.09% in ternary all‐PSCs, where the B→N‐based polymer acceptor was incorporated into the PM6:PY‐IT (regioregular PSMA) host blend.…”

“…The electron‐deficient strength of terminal group in PSMAs could affect not only charge dynamics and energy levels, but also the optical absorption via the ICT effect. The halogenation and conjugation extension strategies in IC‐Br terminal group have provided the facile way to endow the resulting PSMAs (such as PYF‐T‐o and PY2F‐T) not only with a stronger ICT to broaden NIR absorption but also the increased interchain packing for high electron mobility 28,30 . Developing additional innovations (extending the conjugation or introducing the heteroatom) on the electron‐withdrawing terminal groups than fluorinated or chlorinated IC‐Br terminal groups is also a potential approach for further advancing PSMAs.…”

“…Because of the remarkable red-shifted absorption, superior backbone ordering, and optimal blend morphology with the donor component (PBDB-T), PZT-γ-based all-PSCs afforded a record-high power conversion efficiency of 15.8%, a greatly enhanced J sc of 24.7 mA cm À2 T A B L E 1 The reported photovoltaic properties for the regiorandom and regioregular PSMAs based all-PSCs All-polymer systems Their study also highlighted that precise control of the molecular configuration enhanced the charge carrier mobility and decreased the π-π stacking distance, which afforded higher performance in all-PSCs. 28,32,33 Additionally, Liu et al 32 obtained an optimal morphology, reduced nonradiative energy loss, and an impressive PCE of 16.09% in ternary all-PSCs, where the B!N-based polymer acceptor was incorporated into the PM6:PY-IT (regioregular PSMA) host blend. Very recently, Min et al 33 reported a record-high efficiency of 17.2% and superior stability of ternary all-PSCs, which contained the regioregular PSMA PY2F-T.…”

Recent Progress in Organic Solar Cells: A Review on Materials from Acceptor to Donor

“…Furthermore, they synthesized PY2F-T by adopting a difluoro-monobromo end group, IC-2FBr. The performance of PY2F-T-based devices was improved significantly by the fluorination strategy, delivering a device PCE of 15.22% [ 75 ]. Recently, Fu and co-workers developed a series of PZTs as acceptors for all-polymer solar cells based on the benzotriazole-core fused-ring segment.…”

Review on Y6-Based Semiconductor Materials and Their Future Development via Machine Learning

“…Based on PYF-T, Yu and coworkers [90] in 2021 reported a PY2F-T with two fluorine atoms on its one end group, and an all-polymer solar cell with an efficiency of 15.22% [90] was obtained. After introducing the fluorine-free PYT as the third component into the main system of PM6: PY2F-T by Sun and coworkers [91], the improved PCE of PM6:PY2F-T is as high as 17.2% [91] due to a balance between material crystallization and phase separation.…”