Study On The Spectral Characteristics Of Trions In CdSe/znS Quantum Dot Films

Trions(charged excitons) are electron-hole pairs with another electron or hole,whose spectral characteristic is very different from those of neutral excitons and multi-excitons, and hold important implications for the stability and efficiency of photoelectric material. For example in solar cells,generation and evolution of trions is an important process of multi-excitons generation and charge transfer after separation,which affects the photoelectric conversion efficiency a lot. Understanding of trions arises from the florescence blinking and spectral diffusion in QD emitting devices. The advanced ultra-fast spectral techniques and electrochemistry help deepen its study,which also provide more thoughts for development of bioluminescence and electro-optical devices etc.This paper takes Cd Se/Zn S core/shell quantum dot films as main object of study, Time-resolved fluorescence(TRF) spectrum measurement under photo-injection and electric injection as main approaches of research, to study the generation conditions and spectral including dynamics characteristics and also to explore the way of regulating the trions’ spectrum by cation absorption during electric process.First, based on the generation theory of trion, gradually increase the photo-injection level under a suitable frequency to generate trions, take its TR fluorescence spectrum by TCSPC, then extract the component of trions(also biexcitons) by global fitting, and acquire the relative spectral characteristics parameters.Secondly, combine the three-electrode system and Cyclic voltammetric method to directly inject electrons into QD films and do some spectral measurement. Take cross-linked ITO/QD films as the working electrode, Pt disk as the counter electrode and Ag wire as the reference electrode to do cyclic voltammetric scanning in the organic electrolyte and determine the oxidation and reduction peak- 1Se level. And then do the fluorescence and dynamics spectrum measurements under three-electrode voltage regulator system. Combine the electrochemistric and spectral results to analyze the entire electric injection process.Finally, study the method of inducing KCl solution into the organic electrolyte to control the trions’ spectrum.After adding a small amount of KCl solution,the spectrum under negative bias shows opposite shift-blueshift to that with pure organic electrolyte, which have similar PL quench and shortened lifetime. As to the mechanism, we center on the cation absorption, combine the factors of surrounding electric field conversion, surface state change and hole injection to explain.