Light-Induced Charged and Trap States in Colloidal Nanocrystals Detected by Variable Pulse Rate Photoluminescence Spectroscopy

Abstract

Intensity instabilities are a common trademark of the photoluminescence of nanoemitters. This general behavior is commonly attributed to random fluctuations of free charges and activation of charge traps reducing the emission yield intermittently. However, the actual physical origin of this phenomenon is actively debated. Here we devise an experiment, variable pulse rate photoluminescence, to control the accumulation of charges and the activation of charge traps. The dynamics of these states is studied, with pulse repetition frequencies from the single-pulse to the megahertz regime, by monitoring photoluminescence spectrograms with picosecond temporal resolution. We find that both photocharging and charge trapping contribute to photoluminescence quenching, and both processes can be reversibly induced by light. Our spectroscopic technique demonstrates that charge accumulation and trap formation are strongly sensitive to the environment, showing different dynamics when nanocrystals are dispersed in solution or deposited as a film.

Correlated electron–hole plasma in organometal perovskites

“…The low-excitation source was a Ti:sapphire oscillator (Spectra Physics Tsunami) delivering 100-fs-long pulses to a home-made pulse picker to reduce the pulse repetition rate from 80 MHz to 800 Hz (ref. 56). The available energy on the sample surface was in the range 0.1-100 pJ per pulse.…”

Photon-correlation Fourier spectroscopy of the trion fluorescence in thick-shell CdSe/CdS nanocrystals

“…Trapping and movements of charges at the shell-ligands interface result in fluctuations of the local electric field that induce random spectral jumps and broaden the emission linewidth. The dynamics of the SD has received great interest [11][12][13][14] since it limits the use of colloidal NC in applications such as two-photon interference * jean-pierre.hermier@uvsq.fr in the domain of quantum computing for which time coherence is a key point. SD can be studied using either conventional spectroscopic technique, which is based on the acquisition of consecutive photoluminescence (PL) spectra [13], or by more advanced methods.…”

Ultrafast Optical Spectroscopy Techniques Applied to Colloidal Nanocrystals

“…[66,129] Engineering of surface traps to control recombination rate is critical for the design of sensitive and fast photoconductive detectors, while suppres- properties. [3,124,129,[132][133][134][135][136][137] Apart from an early report in Bi 2 S 3 nanocrystals with band gap at 1.7 eV, [138] to the best of our knowledge, no systematic investigation of the excited-state dynamics in bismuth sulfide has been reported until now. shows the presence of rod shaped particles with average sizes of 29 nm (14% polydispersity) and of 14 nm (19% polydispersity).…”