Intraband Exciton Dynamics of n-Doped Silver Selenide Quantum Dots

AgSe (x > 2) colloidal quantum dots (CQDs) have recently emerged as a promising environmentally friendly material contender for mid- and long-wave infrared optoelectronics, leveraging their intraband transition (1S_e-1P_e). However, multicarrier interactions in CQDs, particularly Auger recombination, have profound implications on the optoelectronic properties of the materials and their potential in device applications. Understanding the intraband excited-state dynamics in n-doped AgSe is therefore essential for the assessment and successful implementation of this material platform in devices. We, herein, investigate the carrier dynamics of AgSe in both solution and thin-film states using a femtosecond mid-infrared transient absorption spectrometer. Our observations reveal that the multicarrier Auger process depends on the degree of doping in AgSe CQDs and accelerates when the Fermi energy (E_F) level approaches the 1P_e state. The calculated intraband Auger coefficients (C_A) are measured to be on the order of ∼10^-28 cm⁶ s^-1, significantly larger compared to analogous n-doped HgS/Se CQDs.