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.

Regioregularity-control of conjugated polymers: from synthesis and properties, to photovoltaic device applications

“…RR can also be represented by the positional orientation of covalent bonds between monomer units in CP backbones. [37][38][39][40][41][42] An example of positional RR can be found in poly([N,N 0 -bis(2octyldodecyl)naphthalene-1,4,5,8-bis(dicarboximide)-2,6-diyl]alt-5,5 0 -(2,2 0 -bithiophene)) (P(NDI2OD-T2) or N2200), which is one of the most widely used n-type CPs. [42][43][44] The naphthalene diimide (NDI) repeating moiety of P(NDI2OD-T2) has four different reactive sites for hydrogen, which can be substituted with bromines in the 2,6-or 2,7-position.…”

“…In these systems, non-fullerene small-molecule-acceptor (NFSMA) with multiple fused rings and strong dyes are alternatively copolymerized with donating spacers (i.e., thiophene or selenophene) to yield polymerized NFSMAs (PSMAs). [39][40][41]117,118 The reactive bromides on different positions on the SMA monomer (i.e., 1,1-dicyanomethylene-3-indanone (IC-Br)) result in two different positional isomers of IC-Br units (IC-Br(in) and IC-Br(out)) based on their position relative to other functional groups (i.e., carbonyl and malononitrile groups) (Fig. 7b).…”

A Chlorinated Donor Polymer Achieving High‐Performance Organic Solar Cells with a Wide Range of Polymer Molecular Weight

“…[ 12–21 ] With the help of NFAs, the efficiency of non‐fullerene OSCs has been increased to beyond 17%, showing the bright future of this technology. [ 22–33 ]…”

Printable and stable all-polymer solar cells based on non-conjugated polymer acceptors with excellent mechanical robustness

“…Significant enhancement in device performance of the PZ1 polymer acceptor by this approach can be attributed to its improved light-harvesting properties, including wide absorption range and high absorption coefficient. Subsequently, a series of high performance PSMAs were prepared by screening high performance SMAs building blocks and different conjugation units [25][26][27][28][29][30][31].…”