Charge-transfer complexes and their applications in optoelectronic devices

Abstract

Abstract After several decades of intense researches on organic optoelectronics, several types of optoelectronic devices such as organic light-emitting devices (OLEDs) have become commercially viable and performance of organic photovoltaic (OPV) devices has seen significant progress. At the same time, scientists are getting better understanding on the device physics and the important roles of charge-transfer (CT) states in these devices are widely recognized. CT states are formed upon CT interaction between donor (D) and acceptor (A) molecules. When the extent of CT is high enough, the CT states are specifically referred as charge-transfer complexes (CTCs). Depending on their formation mechanisms, CTCs can be classified into ground-state charge-transfer complexes (GSCs) and excited-state charge-transfer complexes (exciplexes). Novel optoelectronic properties of GSCs, including their abnormally high electrical conductivities, long-wavelength photon absorption, charge-generation, etc. have been applied in various optoelectronic devices. On the other hand, attention of excited CTCs is primarily focused on exciplex emission and CT absorption. Recent experimental evidence deepens the understanding of CT states and their new applications are exploited. Since there are limited systematic reviews on application of CTCs in different organic devices, this review intends to fill this gap by giving a brief overview of novel CTC applications and correlating CT properties with device performance.