Efficient Hot Electron Transfer and Improved Lifetime of Charge Carriers at The 1P Hot State in Sb₂Se₃/CdSe p-n Heterojunction

Utilization of hot carriers is very crucial in improving the efficiency of solar energy devices. In this work, we have fabricated Sb₂Se₃/CdSe p-n heterojunction through cation exchange process for the very first time and explored their interfacial photophysical processes with help of ultrafast transient absorption spectroscopy. In the transient study, the heterosystem was consisted with both the signature of Sb₂Se₃ and CdSe. Interestingly, the 1P excitonic bleach was found to be more prominent in the heterosystem. This is itself a testimony for hot electron migration from Sb₂Se₃ to CdSe QDs. From the comparative dynamic profiles, we found that both the 1P and 1S bleach signals are slower in the heterosystem, which again substantiates the electron migration phenomena. In fact, the hetero-system slowed down the 1P signal more efficiently than that of the 1S one. This is an incredible observation, as hot electron migration influenced the separation of charge carriers in a hot excitonic state (1P), not in the usual lowest excitonic state (1S). Enhanced charge carrier lifetime of the hot state would be helpful in the extraction of those charge carriers in a device set up. Our detailed spectroscopic investigation in this p-n heterojunction would help in the fabrication of many new heterojunctions and uplift the field of condensed matter based opto-electronic devices.