Introducing Ag Dopants into CdSe Nanoplatelets (NPLs) Leads to Effective Charge Separation for Better Photodetector Performance.

Abstract

Solution-processed colloidal cadmium chalcogenide nanoplatelets (NPLs)-based photodetectors (PD) are promising materials for next-generation optoelectronic devices due to their excellent optical properties. Here, we report on ultrafast carrier relaxation dynamics of four monolayer (4 ML) Ag-doped CdSe (Ag: CdSe) NPLs using ultrafast transient absorption spectroscopy and their photodetectors applications. A broad dopant emission is observed at around 650 nm with a large FWHM of ~431 meV and band edge emission at 515 nm. The intragap dopant state acts as a hole acceptor, which leads to better charge separation. The ultrafast transient absorption spectroscopy study shows faster carrier recombination dynamics with a hole transfer time scale of ~10 ps in Ag-doped CdSe NPLs. This supports the excited hole capture phenomenon at the dopant state. Ag-doped CdSe NPLs-based PD performed better than undoped CdSe NPLs with detectivity and responsivity values of 1.3×1010 Jones and 2.4 mA/W, respectively.