Electronic effect of substituents on the charge-transfer dynamics at the CsPbBr3 perovskite-small molecule interface

To push the boundary of the efficiency of perovskite nanocrystal-based photovoltaics, understanding the charge transfer at the interface of these nanocrystals is necessary. In an effort to understand the electronic effects of the substituents in the charge acceptor moiety, three electronically different small molecules (namely, chloranilic acid (CA), p-benzoquinone (BQ), and duroquinone (DQ)) were chosen and their detailed charge transfer dynamics were studied at the CsPbBr3 perovskite nanocrystal-small organic molecule interface using steady state and time-resolved spectroscopic methods. The steady-state absorption and time-resolved emission studies reveal that all three molecules interact with the NCs in the excited state. Femtosecond transient absorption experiments indicate a faster ground-state bleach recovery in the presence of the three acceptors, compared with the pristine NCs. Utilizing band alignment analysis, the faster bleach recovery of the NCs in presence of the acceptors was confirmed to be because of electron transfer from the photo-excited NCs to the acceptor molecules. Moreover, the electron transfer rates fall in the Marcus normal region and can be explained based on the electronic effects of the substituents present on the acceptor molecules.

Automated summary

To enhance the efficiency of perovskite nanocrystal-based photovoltaics, studying the charge transfer at the nanocrystal interface is crucial. In this study, three small molecules with different electronic properties were chosen to investigate their charge transfer dynamics at the CsPbBr3 perovskite nanocrystal-small organic molecule interface. The results showed that these molecules interacted with the nanocrystals in the excited state, and electron transfer from the nanocrystals to the acceptor molecules was confirmed to be the reason for faster ground-state bleach recovery.