Interfacial Charge-Carrier Dynamics in CuPc/CdSe Excitonic Heterostructures Studied by Pump–Probe Spectroscopy

Investigating interfacial charge carrier dynamics is important for improving the efficiency of photovoltaic devices with organic and inorganic heterostructures to exceed the Shockley–Queisser limit. Charge transfer dynamics at the organic/inorganic interfaces with two different types of excitons are still unclear. In this work, we reveal the photogenerated charge carrier dynamics at the interface of CuPc/CdSe nanoflakes using steady-state and transient reflection spectroscopy. The CuPc layer deposited on CdSe effectively modifies the charge carrier dynamics, reducing the fast electron lifetime from 10.96 to 3.12 ps. Following photonic interaction with ZB-CdSe, the photogenerated electrons are transferred to CuPc, forming a singlet charge transfer state (¹CT). Rapid intersystem crossing converts this into a triplet state (³CT), preventing electrons return to CdSe and enabling efficient exciton dissociation into long-lived polarons in CuPc with longer lifetimes. The results show that an enhanced red-shift around 20 nm, caused by a decrease in the bandgap, ultimately improves the overall charge transfer efficiency, η ∼ 70% at CuPc/ZB-CdSe interfaces, comparable to that achieved in quantum dot systems. Our work demonstrates an effective pathway for improving the photoelectric performance of CuPc/CdSe composites to get electrons out from CdSe, which involves transporting them across CuPc/CdSe interfaces.