Optical Transitions in Silver Indium Selenide Nanocrystals: Implications for Light-Emitting and Light-Imaging Applications

Abstract

Among the alternatives for the successful family of Cd-and Pb-chalcogenide nanocrystals (NCs), I−III−VI NCs appear to be highly promising as they combine low toxicity with up-and-coming light-emitting and light-imaging applications. Much of the focus has been placed on the prototype Cu−In−S NC system, while Ag-based NCs are significantly less developed. Herein we report spectroscopic studies of robust Ag 3 In 5 Se 9 NCs fabricated via an amide-promoted synthesis, using NC size as the structural varying parameter. Temperature-dependent photoluminescence, combined with Gaussian line-shape analysis, reveals the presence of three radiative channels in colloids and films of the Ag 3 In 5 Se 9 NCs. On the basis of their energetics, dynamics, and size-and temperature-dependent behavior, we assign the radiative channels to optical transitions from the conduction-band minimum to (i) in-gap states of self-trapped holes, (ii) valence-band maximum, and (iii) lower-energy valence-band states. Furthermore, by combining pump−probe experiments with tight-binding band-structure calculations whose parameters were derived from first principles, we reveal the presence of two main interband absorption transitions associated with NC electronic states. The dynamics of such transitions are influenced by shallow surface states that act as sites in which fast exciton trapping and much slower detrapping occurs, whereas the trapping and detrapping rates are gauged by confinement and temperature.

Synthesis and Electronic Structure of Mid-Infrared Absorbing Cu3SbSe4 and CuxSbSe4 Nanocrystals

“…Strong optical coupling with the d -type valence band wavefunctions (Figures c and S12) implies that absorption will primarily occur from the top of the valence band to the triplet states in the conduction band. These characteristics are similar to those of I–III–VI nanocrystals, previously studied with tight-binding simulations …”

“…These characteristics are similar to those of I–III–VI nanocrystals, previously studied with tight-binding simulations. 41 …”

“…These characteristics are similar to those of I−III−VI nanocrystals, previously studied with tight-binding simulations. 41 A 9.5 nm nanocrystal has a band gap of 0.3 eV and a main absorption feature from the valence band to the triplet states at 0.38 eV (Figure S13). Reducing the nanocrystal size from 9.5 to 7.5 nm increases the band gap from 0.3 to 0.35 eV, and the 10% size variation in nanocrystals observed experimentally could lead up to a 50 meV spread in band gap energies (Figure S14a).…”

Unraveling the Origin of Long-Lifetime Emission in Low-Dimensional Copper Halides via a Magneto-optical Study

“…The Cs + -crown ether complexes and DMSO molecules primarily serve to stabilize the [Cu Figure 2a shows the contour plot of PL spectra at various temperatures ranging from 0.2 to 300 K. It is evident that the PL spectrum narrows, and the intensity increases as the temperature decreases from 300 to 20 K (Figure 2b), indicating the suppression of electron−phonon coupling and nonradiative recombination at low temperatures. 25,28 This is further confirmed by the TRPL measurements at different temperatures (Figure 2c), showing that the PL lifetime gradually increases from 1.3 to 5.4 μs as the temperature decreases from 300 to 20 K (Table 1). By comparing the temperature-dependent PL and TRPL measurements, we obtained the radiative and nonradiative recombination rates as a function of temperature (Figure 2d).…”

Template-Based Controlled Synthesis and Bioapplication of AgInSe2:Zn2+ Near-Infrared Luminescent Quantum Dots※

“…目前, AISe 量子点的主要合成方法为直接合成 法 [21][22] , 是将所有的原料一起加热成核或者在高温下注 入非金属元素. 这样的合成法虽然直接、快速, 但对于 组分和形貌的调控却不理想, 原因在于多个阳离子和阴 离子前驱体之间表现出不同的反应活性.…”