Tunable Light Response Modulated by the Organic Interface Charge Transfer Effect

The combination of a donor (D) and an acceptor (A) is viewed as a promising approach to achieve high performance phototransistors, owing to their advantages in exciton dissociation and charge trapping. The electronic properties at the D-A interface can vary substantially with the choice of materials, and how to precisely control the interface properties to achieve a controllable light response behavior is still an open question. Herein, a series of D-A heterostructure is reported with varying electronic structures of the acceptor and demonstrate the ability to tune the performance and photocurrent decay behaviors. Two distinct types of charge transfer phenomena, ground state, and excited state charge transfer, are identified originating from the specific different energy level alignment and lead to the improved photoresponsivity up to 104 AW-1 and the significantly varied photosensitivity ranging from 102 to approaching 107. Furthermore, the distinct charge transfer scenarios elicit diverse temporal responses, encompassing both short-term synaptic behavior as well as persistent memory characteristics. These findings shed light on the importance of understanding and controlling charge transfer property for phototransistor performance and applications. The ability to modulate the temporal responses opens up new possibilities for designing devices with desired memory and synaptic functionalities. The adjustion of different D-A combination in organic heterostructure phototransistors is investigated comprehensively, realizing two distinct types of charge transfer effects, ground state, and excited state charge transfer. The electronic properties of the D-A interface is proven to controllably tune the photoresponse performance and photocurrent decay behaviors, providing a new path for designing and optimizing the devices of D-A organic heterostructures.image