Manipulation of Molecular Motion in Donor‐Acceptor Organic‐Small‐Molecule towards Efficient Solar‐Thermal Conversion and Electroluminescence Performance

Abstract

ABSTRACT Radiative decay invariably competes with nonradiative decay during the deexcitation process of materials, organic small molecules with highly efficient solar‐thermal and electroluminescence properties simultaneously remain a great challenge. Herein, we propose a novel strategy to achieve simultaneously efficient solar‐thermal and electroluminescence systems based on one molecule by manipulating molecular motion (MM) in aggregates. The proof‐of‐concept organic‐small‐molecule t ‐GDPA‐QCN was developed, where the donor group with a relatively large steric hindrance, the planar acceptor quinoxaline‐6,7‐dicarbonitrile (QCN), was conjugated with the dendritic triphenylamine ( t ‐GDPA) through a phenyl spacer, forming an umbrella‐like donor‐acceptor (D‐A) motif. Because a loose packing mode in pure solid state facilitates MM and consequently elevates nonradiative decay, t ‐GDPA‐QCN shows a solar absorptivity of 37.56%, which leads to superior water evaporation and electricity generation performances. Furthermore, when t ‐GDPA‐QCN is doped into a host material with a suitable size, the MM is effectively restricted, resulting in low nonradiative transitions. Consequently, deep‐red organic light‐emitting diodes (OLEDs) with excellent performance were realized, achieving a maximum external quantum efficiency (EQE) of 3.2% at an emission peak of 664 nm. This work represents the first example of organic‐small‐molecules featuring efficient photothermal and electroluminescence conversion systems simultaneously.