有机太阳能电池中基于苝二酰亚胺结构小分子受体进展

Recent Progress in Perylene Diimide-Based Small Molecule Acceptors for Organic Solar Cells

最近几年,有机太阳能电池中的非富勒烯小分子受体研究引起了人们的兴趣。其中,苝二酰亚胺(PDI)类分子因具有良好的电子传输能力,较强的电子亲和力,稳定的光、热、化学性能以及化学结构的可设计性带来的性能可调控性而得到广泛的关注。本文总结了近三年来在体异质结有机太阳能电池应用方面PDI小分子受体的研究进展,重点关注了PDI分子结构对其性能的影响,希望为以后PDI类受体分子的设计思路起到一定的启发作用。

In recent years, non-fullerene small molecule acceptors for organic solar cells (OSCs) have attracted much research attention. Among them, perylene diimide (PDI) and its derivatives are widely investigated due to their excellent electron mobility, high electron affinity, thermal and photochemical stability, and the feasibility with which they can be chemically modified. However, the utilization of PDIs in OSCs still lags behind that of fullerenes. This is mainly because the PDI-based acceptors possess strong ππ stacking, and therefore they are inclined to form large aggregates in bulk heterojunction (BHJ) active layers. Structural modification of PDIs by disrupting their planarity plays a vital role for the application of these novel acceptors in high-performance OSCs. In this review, progresses in PDI-based small molecule acceptors for BHJ OSCs in the past three years are summarized. This work focuses on the development of molecular structures and the optimization of the power conversion efficiency (PCE) of devices. The modifications in the molecular structures are introduced according to the active PDI reaction sites, including the bay positions, ortho positions, and imide positions, to disturb the planarity and construct twisted configurations. Modifications at the bay positions are considered to be the most common and efficient;they may form PDI multimers such as dimers, trimers, and tetramers possessing quasi-3D nonplanar structures. The progress in such modifications is discussed at length. Substitutions at the imide positions are chemically simple but less effective in changing the planarity of the molecular backbone. Nevertheless, they may alter the solubility of the molecules, the film morphology, and thereby the efficiency of the devices. Functionalization of ortho positions can also effectively improve the performance of devices, but they are synthetically difficult. For conjugated PDI molecules fused at the bay positions, the properties of exciton diffusion, charge mobility and charge separation, and thereby the device performance, may be modulated by the molecular planarity, the number of the fusing unit, and the axis direction, which in turn determine the packing modes and the extent of π-extension. In summary, the photoelectric properties of PDI-based acceptors can be adjusted via various modification methods, and the relationships between the molecular structure and photovoltaic performances should be further explored.