Ultrafast charge dynamics in novel colloidal quantum dots

摘要: In this thesis ultrafast exciton dynamics of several colloidal quantum dots have been studied using visible transient absorption spectroscopy. The resultant decays and differential transmission spectra were analysed to determine the relaxation channels, multiple generation (MEG) efficiency multi-exciton interactions in observed materials. All QDs preliminarily optically characterized steady state photoluminescence spectroscopies. addition, a high repetition infrared femtosecond pump probe experiment was designed built detect picosecond intraband carrier relaxations dots.Picosecond type-II ZnTe/ZnSe CuInSe2 CuInS2 type-I investigated. common feature these materials is that they are eco-friendly materials, being alternatives toxic Cd- Pb- based It found surface trapping occurred both cases for electrons hot states, minimum conduction band core/shell Trion formation at power unstirred conditions. cold electron processes shifted, distorted moderately cancelled bleach features. intra-gap hole which results long decay recorded transients.MEG competes with Auger cooling, mediated phonon emission. To enhance MEG yield, rival mechanisms suppressed well-engineered CdSe/CdTe/CdS CdTe/CdSe/CdS core/shell/shell CdTe/CdS dots. slope threshold range different core size shell thickness be (142�9)%/Eg (2.59�0.16)Eg, respectively. consistent literature, whereas, obtained about three times higher than previously reported values.The biexciton interaction energy stated previous paragraph also studied. date, time-resolved (TRPL) has employed study large repulsive values between 50-100 meV reported. However, unlike TRPL method, TA ensures only two excitons remain edge dot. Using attractive energies up ~-60 observed. These promising implications regarding enhancing yield.