Optoelectronic properties and ultrafast carrier dynamics of copper iodide thin films

Abstract

As a promising high mobility p-type wide bandgap semiconductor, copper iodide has received increasing attention in recent years. However, the defect physics/evolution are still controversial, and particularly the ultrafast carrier and exciton dynamics in copper iodide has rarely been investigated. Here, we study these fundamental properties for copper iodide thin films by a synergistic approach employing a combination of analytical techniques. Steady-state photoluminescence spectra reveal that the emission at ~420 nm arises from the recombination of electrons with neutral copper vacancies. The photogenerated carrier density dependent ultrafast physical processes are elucidated with using the femtosecond transient absorption spectroscopy. Both the effects of hot-phonon bottleneck and the Auger heating significantly slow down the cooling rate of hot-carriers in the case of high excitation density. The effect of defects on the carrier recombination and the two-photon induced ultrafast carrier dynamics are also investigated. These findings are crucial to the optoelectronic applications of copper iodide.

Rashba Band Splitting and Bulk Photovoltaic Effect Induced by Halogen Bonds in Hybrid Layered Perovskites

“…[17a, 21] Typically, the radiative recombination rate is in the order of 10 À 11 to 10 À 9 cm 3 s À 1 in GaAs and hybrid perovskites. [21,22] However, the second-order recombination rate for n = 2 samples shows great variation (k 2 � 0), while the values of k 2 for the others are comparable to that for similar hybrid perovskites in the literature. [17b, 19b] In the presence of Rashba splitting, the magnitude of splitting is different in the valence and conduction bands, and an indirect transition is induced.…”

Spectroscopic Investigation of Structural Perturbations in CsPbCl3 Perovskite Nanocrystals: Temperature- and Excitation-Energy-Dependent Study

“…To further emphasize our results, we have calculated the T c (Figure A–C) for CsPbCl 3 NCs for all temperatures under consideration. In order to calculate T c , the high-energy tail of the normalized TA bleach is fitted using the Maxwell–Boltzmann (MB) approximation. − The detailed explanation of the procedure followed and plots of MB fitting are provided in the Supporting Information (Figure S10). However, after being stimulated by an ultrashort pulse, both holes and electrons populate the higher energy levels rapidly and thermalize within sub picoseconds. ,, They eventually relax to the band edge via carrier–carrier scattering, carrier–phonon scattering, and phonon–phonon scattering .…”

“…64 Similar behavior in perovskites has been observed by employing OPTP spectroscopy, and these investigations observed a faster response component (Auger recombination) with increased pump fluences. 49,64,65 Thus, it is fair to ascertain that both absence of Auger recombination process as well as higher penetration depth upon lower pump excitation govern the slower decay of mobility and photoconductivity upon near band gap excitation (Figure 5F).…”

Carrier Dynamics in Solution-Processed CuI as a P-Type Semiconductor: The Origin of Negative Photoconductivity

“…In a material where the Coulombic interaction between the hole and electron pair is strong, such as in the case of CuI, photoexcitation could give rise to bound excitons (CuI exciton binding energy is ≈62 meV) . Li et al observed an ultrafast negative transient absorption signal at 3.7 eV (0.65 eV higher energy than the bandgap bleach signal), which they assigned to free excitons, confirming the existence of strongly bounded excitons. Excitons are quasi-particles formed by bound hole–electron pairs, which in the case of CuI excited at 550 nm, would appear when promoting an electron from the VB to a trap state.…”