Modulating Energy Level on an A‐D‐A′‐D‐A‐Type Unfused Acceptor by a Benzothiadiazole Core Enables Organic Solar Cells with Simple Procedure and High Performance

Abstract

Unfused‐ring acceptors (UFAs) have gained considerable research attention as they offer simple chemical structures through simplified synthesis methods, which would boost the commercialization of organic solar cells (OSCs). Recently, a new small molecule acceptor (SMA) named Y6 was reported, yielding high‐performance OSCs. Herein, the Y6‐like A‐DA′D‐A framework is developed to A‐D‐A′‐D‐A‐type backbone adopted in constructing UFAs. Two new Y6‐like UFAs are synthesized within four steps and the effect of noncovalent atoms at the central electron‐deficient core on material properties and device performances is studied. It is found that the introduction of fluorine atoms can bring larger red‐shift in the absorption spectra and better aggregation of the resulting UFA film states compared with those of oxygen atoms. Interestingly, the variations in the noncovalent interaction atoms induce different intermolecular charge transfer between donors and UFAs. When blended with another economical donor, PTQ10, F substitution at the benzothiadiazole ring is more effective than O substitution, leading to the increased short‐circuit current density (JSC) and higher efficiency of over 12%, among the best performances of UFA‐based OSCs. This contribution demonstrates the appropriate introduction of noncovalent interaction is a promising method for tuning energy levels, absorption, and aggregation of UFAs for high‐performance OSCs.

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

“…In contrast, the PYF-T-and PYF-To-based devices presented efficient charge dissociation with P(E, T) of 97.5 %a nd 98.3 %r espectively,t hus partially explaining the dramatically enhanced J SC in PYF-T and PYF-T-o-based all-PSCs with stronger conjugated polymer acceptors. [56] Apart from the variations in J SC ,i ti sa lso intriguing to reveal the reasons for the enormous differences in FF of the all-PSCs based on these fluorinated polymer acceptors from the perspective of charge extraction and recombination. Hence,t ransient photocurrent (TPC) and transient photovoltage (TPV) techniques were conducted for the three all-PSCs.…”

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

“…[41][42][43] In particular, fluorination is the most commonly adopted strategy to promote dense solid-state packing due to the small atomic size of the F atom, and more importantly, the formation of multiple intra-or intermolecular non-covalent interactions, such as the F•••H and F•••S interactions. [44][45][46] In addition, the strong electron-withdrawing ability of F atoms can dramatically alter the electronic structure of the materials, leading to the tunability of energy levels and optical absorption. [47][48][49] Apart from the modulations of optoelectronic properties, F atoms in the polymer backbone can also provide kinetic (dense intermolecular packing) as well as energetic (downshifted energy levels) barriers to oxygen and moisture.…”

Fluorinated End Group Enables High‐Performance All‐Polymer Solar Cells with Near‐Infrared Absorption and Enhanced Device Efficiency over 14%

“…In fact, fluorination of the end groups in the A-D-A type SMAs has already been proved to be a successful strategy to improve J SC , intermolecular aggregation and thus device performance. [37,38] Therefore, the fluorination on the end groups of SMA units of polymer acceptor may provide another approach to designing high-performing polymer acceptors.…”