High‐Performance Noncovalently Fused‐Ring Electron Acceptors for Organic Solar Cells Enabled by Noncovalent Intramolecular Interactions and End‐Group Engineering

Abstract

Noncovalently fused‐ring electron acceptors (NFREAs) have attracted much attention in recent years owing to their advantages of simple synthetic routes, high yields and low costs. However, the efficiencies of NFREAs based organic solar cells (OSCs) are still far behind those of fused‐ring electron acceptors (FREAs). Herein, a series of NFREAs with S⋅⋅⋅O noncovalent intramolecular interactions were designed and synthesized with a two‐step synthetic route. Upon introducing π‐extended end‐groups into the backbones, the electronic properties, charge transport, film morphology, and energy loss were precisely tuned by fine‐tuning the degree of multi‐fluorination. As a result, a record PCE of 14.53 % in labs and a certified PCE of 13.8 % for NFREAs based devices were obtained. This contribution demonstrated that combining the strategies of noncovalent conformational locks and π‐extended end‐group engineering is a simple and effective way to explore high‐performance NFREAs.

Regioregular Narrow‐Bandgap n‐Type Polymers with High Electron Mobility Enabling Highly Efficient All‐Polymer Solar Cells

“…In contrast, PM6:MBTI film has a significantly rougher morphology with a RMS surface roughness of 1.97 nm, which could negatively affect the charge generation and transfer. [ 50 ] Therefore, a relatively poor J sc and FF values were observed in the PM6:MBTI binary devices. The TEM images also indicate that the ternary film can form nanoscale phase separated morphologies with appropriate domain sizes (Figure 4i–l).…”

Regulating the Aggregation of Unfused Non‐Fullerene Acceptors via Molecular Engineering towards Efficient Polymer Solar Cells

“…[16][17][18][19] As an alternative candidate to alleviate above issues, unfused non-fullerene acceptors (UF-NFAs) have attracted broad interest recently. [19][20][21] However, the current PCEs of UF-NFAs-based PSCs [22][23][24][25][26][27][28][29] still lag behind those based on F-NFAs. Therefore, the development of efficient UF-NFAs is of great urgency.…”

“…Over the past few years, molecular design for high-performance UF-NFAs mainly focused on planarizing molecular backbone through non-covalent conformational locking, which has been proved as an effective strategy for efficient charge transport. [22][23][24][25][26][27][28][29] However, the correlation between device performance and the bulk-heterojunction active layer morphology in terms of the molecular conformations [26,27] and molecular packing patterns, [30][31][32][33][34][35][36][37][38] still remains unclear in the field of UF-NFAs. As revealed by our recent work on crystallographic analysis of highly efficient Y6 and CH1007 F-NFAs, [10] π-core interaction plays a crucial role in regulating the molecular geometry and triggering unique self-assembly that benefit photovoltaic performance.…”

Side‐Chain Engineering for Enhancing the Molecular Rigidity and Photovoltaic Performance of Noncovalently Fused‐Ring Electron Acceptors

“…Therefore, NFREAs are feasible to synthesize, possess much better solubility and processability than FREAs, impart the desired dynamic nature to allow better molecular crystallization and ordered packing [10] . Our group has devoted significant efforts to develop NFREAs, and achieved the certified PCE of 13.8 % very recently [8d] . However, the PCEs of NFREAs still lag far behind those of FREAs.…”