posted on 2021-03-08, 21:06authored byGoutam Ghosh, Kritiman Marjit, Srijon Ghosh, Arnab Ghosh, Raihan Ahammed, Abir De Sarkar, Amitava Patra
A deep
understanding of hot carrier (HC) dynamics is important
to improve the performance of optoelectronic devices by reducing the
thermalization losses. Here, we investigate the hot hole cooling and
transfer dynamics of CsPbBr3 nanocrystals (NCs) using 5,10,15,20-tetra(4pyridyl)
porphyrin (TpyP) molecules. Density functional theory (DFT) is used
to elucidate the mechanism underlying charge extraction as well as
the HC transfer process in the CsPbBr3–TpyP system.
It is noted that the hot hole states are localized around the top
surface of CsPbBr3, while the hot electron states are delocalized
away from its top surface, indicating easy extraction of hot holes
from the CsPbBr3 by TpyP molecules, as compared to the
hot electrons. The significant drop of initial hot carrier temperature
from 1140 to 638 K at 400 nm excitation confirms the hot hole transfer
from CsPbBr3 NCs to TpyP molecules, which is dependent
on the excitation energy, and the maximum transfer efficiency is found
to be 42% (for 0.85 eV above band edge photoexcitation). In addition,
the hot hole transfer rate is almost 11 times faster than the band
edge hole transfer rate. Our findings are relevant for the development
of next-generation perovskite-based optoelectronic devices.