Contributed
Charge transfer processes and energy level modifications in CsPbBr₃-CdSe nanoplatelets hybrids coupled by molecular linkers

Merging the benefit of inorganic lead halide perovskite nanocrystals as a superb sensitizer in photovoltaic applications with the spectroscopic tunability and stability of colloidal quantum dots could have great potential prospective for next generation photovoltaic and optoelectronic devices. Here, we have studied the nature of electronic coupling and photo-induced charge transfer occurring in CsPbBr₃-CdSe nanoplatelet hybrid systems cross-linked with short chain Glycine and p-Aminobenzoic acid molecular linkers. Combining photoluminescence spectroscopy and transient absorption measurements in correlation with in-situ photo-response X-ray photoelectron spectroscopy (XPS), we provide comprehensive information on energy level modifications and Fermi level equilibration in our hybrid films. While literature values as well as the experimental data for the band offsets between CdSe and CsPbBr₃ would suggest a type-II band alignment between the two materials. Interestingly, such a feature was not realized in practice in the hybrid films. Instead, we got a pronounced field across the interface and nearly zero band offsets. Remarkably, these hybrid systems generate an effective p-n junction with a built in electric field as controlled by the molecular linkers. As such, it establishes new insight on these potential hybrid systems with potential implications on the design of hybrid p-n photovoltaic devices.