Regio‐Regular Polymer Acceptors Enabled by Determined Fluorination on End Groups for All‐Polymer Solar Cells with 15.2 % Efficiency

Abstract

Polymerization sites of small molecule acceptors (SMAs) play vital roles in determining device performance of all-polymer solar cells (all-PSCs). Different from our recent work about fluoro-and bromo-co-modified end group of IC-FBr (a mixture of IC-FBr1 and IC-FBr2), in this paper,w e synthesized and purified two regiospecific fluoro-and bromosubstituted end groups (IC-FBr-o &I C-FBr-m), which were then employed to construct two regio-regular polymer acceptors named PYF-T-o and PYF-T-m, respectively.Incomparison with its isomeric counterparts named PYF-T-m with different conjugated coupling sites,P YF-T-o exhibits stronger and bathochromic absorption to achieve better photon harvesting. Meanwhile,PYF-T-o adopts more ordered inter-chain packing and suitable phase separation after blending with the donor polymer PM6, which resulted in suppressed charge recombination and efficient charge transport. Strikingly,w eo bserved ad ramatic performance difference between the two isomeric polymer acceptors PYF-T-o and PYF-T-m. While devices based on PM6:PYF-T-o can yield power conversion efficiency (PCE) of 15.2 %, devices based on PM6:PYF-T-m only show poor efficiencies of 1.4 %. This work demonstrates the success of configuration-unique fluorinated end groups in designing high-performance regular polymer acceptors,w hich provides guidelines towardsdeveloping all-PSCs with better efficiencies.

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

“…A plausible explanation is that PY2F-T which owns a better-conjugated coupling site could form suitable phase segregation in the blend, benefitting for the device fabrication with non-halogen solvent, however, the other type of coupling site in PY-T would result in oversized domain size in the blend and thus poor solubility and worse performance through XY processing. [74] Finally, we accessed the shelf-life stability of the two encapsulated all-PSCs (Figure 7b), in which the PY2F-T-based devices demonstrated robust performance after 200 h with only a 4% decrease, while the PY-Tbased ones exhibited inferior stability degraded by 10%. These results suggest that the PY2F-T-based all-PSCs are relatively insensitive to not only water/oxygen but also processing solvents, which is one of the prerequisites for large-scale production of all-PSCs.…”

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

“…Two regionally specific polymer acceptors named PYT-T-o and PYF-T-m had been prepared by Yu and coworkers [89] by 2021. Compared with the random polymer PYF-T and PYF-T-m with weaker conjugation and the intramolecular charge transfer effect, PYF-T-o shows a more regular molecular arrangement, stronger and red-shifted absorption, and more ideal phase separation, all of which lead to the device efficiency of PM6:PYF-T-o to 15.2% [89].…”

π-Conjugated Polymers and Their Application in Organic and Hybrid Organic-Silicon Solar Cells

“…Since the breakthrough of organic solar cells in late 1958, their attention has been rapidly growing in the solar cell community owing to their flexibility, ease of processability, light weight, abundancy of raw materials, ease of synthesis of organic materials, and low fabrication or production costs [165,166]. Much of the success is due to the development of the bulk heterojunction (BHJ) solar cells which provides an enhanced charge separation path-length due to the increased donor-acceptor (D-A) interface, where the charges are separated efficiently [167].…”