A Simple Building Block with Noncovalently Conformational Locks towards Constructing Low-Cost and High-Performance Nonfused Ring Electron Acceptors

Nonfused ring electron acceptors (NFREAs) have attracted much attention due to their concise synthetic routes and low cost. However, developing high-performance NFREAs with simple structure remains a great challenge. In this work, a simple building block (POBT) with noncovalently conformational locks (NoCLs) was designed and synthesized. Single-crystal X-ray study indicated the presence of SMIDLINE HORIZONTAL ELLIPSISO NOCLs in POBT, thus enabling it to possess a coplanar conformation comparable to that of fused-ring CPT. Two novel NFREAs based on CPT and POBT were developed, namely TT-CPT and TT-POBT, respectively. Besides, TT-POBT possessed a smaller Stokes shift and a reduced reorganization energy compared with TT-CPT, indicating the introduction of SMIDLINE HORIZONTAL ELLIPSISO NoCLs can enhance the molecular rigidity even if simplifying the molecular structure. As a result, the TT-POBT-based PSC device afforded an impressive power conversion efficiency of 11.15%, much higher than that of TT-CPT counterpart (7.03%), mainly resulting from the tighter pi-pi stacking, improved and balanced charge transport, and more favorable film morphology. This work demonstrates the potential of the simple building block POBT with NoCLs towards constructing low-cost and high-performance NFREAs.

Automated summary

This work presents the design and synthesis of a simple building block (POBT) with noncovalently conformational locks (NoCLs) for developing high-performance nonfused ring electron acceptors (NFREAs). The introduction of NoCLs enhances the molecular rigidity of the NFREAs and leads to improved power conversion efficiency in the photovoltaic device based on TT-POBT.