Effect of Cu-ion Doping on Hot Electron Relaxation in CdSe Nanorods

Hot electrons in semiconductors have excess energy compared to the band gap, and their utilization holds promise for enhancing the efficiency of photoenergy conversion materials. Copper doping has emerged as a powerful strategy for suppressing hot electron relaxation in colloidal quantum dots (QDs). However, their impact on nanorods (NRs) remains unclear. NRs exhibit a substantial absorption cross-section relative to QDs, rendering them promising materials for enhancing the photoenergy conversion efficiency. In this study, we synthesized Cu-doped CdSe NRs and analyzed their elementary exciton processes using picosecond luminescence decay and femtosecond transient absorption spectroscopy. Although Cu-ion doping slightly suppressed the relaxation of hot electrons, its efficacy was not comparable to that observed in QDs, even with ~10 % Cu ions doping. Temperature-dependent experiments revealed that the relaxation of hot electrons in CdSe NRs proceeds mainly by phonon scattering. This research offers a foundational framework for hot electron utilization in NRs, highlighting the pivotal role of phonon manipulation in effectively harnessing their potential.