A research team at the Dalian Institute of Chemical Physics (DICP) in the Chinese Academy of Sciences synthesized a new lead-free double perovskite nanocrystals (NCs) and revealed the hot-carrier dynamic of it.
To avoid the toxicity issue of Pb, many efforts of finding a possible replacement are made. "We prepared the lead-free 3D double perovskite NCs and demonstrated that the continuously tunable emission ranged from 395 to 575 nm," said the researchers.
The team conducted comprehensive spectroscopic characterizations of the double perovskite NCs, such as absorption cross-sections, carrier recombination, trapping dynamics, and hot-carrier relaxation processes by using time-resolved PL (TR-PL) and femtosecond (fs) transient absorption (TA) spectroscopies in order to clarify the charge carrier dynamics of the double perovskites NCs.
The double perovskite NCs reportedly exhibited a prominent sub-bandgap trapping process, which was related to the surface defects. The ultrafast hot-carrier relaxation processes (less than one ps) were also observed in Cs2AgBiBr6 NCs, which competed with the sub-bandgap trapping process.
The team proposed that the key measure for improving the PL of double perovskite NCs was to decrease the surface defects.