Transient Energy Reservoir in 2D Perovskites

Abstract

Two-dimensional (2D) Ruddlesden−Popper type perovskites have attracted enormous attention due to their natural multi-quantum-well structure. However, there is still mystery regarding the behaviour of photo-carriers, especially the exciton fine structure behind the excellent optoelectronic performance. The coexistence of two strikingly different decay components in time-resolved photoluminescence (TRPL) is inconsistent with the high internal quantum yield ( =~0.7) in the conventional model for radiative and nonradiative recombinations ( ⁄ ). Here we reveal that there is a special transient energy reservoir outcompeting nonradiative loss in 2D Ruddlesden−Popper type perovskites. Upon optical excitation, the bright excitons rapidly relax into the low-lying energy reservoir before nonradiative recombination occurs. Interestingly, the energy in the reservoir is not lost. The carriers in this energy reservoir can spontaneously transfer back to the bright states and can still effectively contribute to the photovoltaic and photonic properties of the perovskites. This investigation provides a novel insight into the mechanism for the lauded defect tolerance of 2D perovskites by highly efficient energy storage via a transient reservoir.

Charge Transport in 2D Layered Mixed Sn–Pb Perovskite Thin Films for Field‐Effect Transistors

“…To evaluate the impact of the Sn–Pb ratio on the carrier lifetime, the TRPL spectra of the (PEA) 2 Sn x Pb 1− x I 4 ( x = 0, 0.3, 0.5, 0.7, 1) thin films are displayed in Figure 2d. They can be well fitted by a biexponential decay (Equation (S1), Supporting Information) [ 31 ] and carrier lifetimes τ 1 and τ 2 are derived and summarized in Table S1 (Supporting Information). τ 1 represents the fast process attributed to the radiative recombination of electrons and holes, and τ 2 is the slow decay process corresponding to the defect‐assisted nonradiative recombination.…”

Suppressing Strong Exciton–Phonon Coupling in Blue Perovskite Nanoplatelet Solids by Binary Systems

“…On one hand, the self-trapping exciton will not absolutely result in nonradiative decay,t he trapped excitons in the band edge possibly recover to free exciton under strong phonon vibrations,t hereby we can see al onger fluorescence lifetime. [17] On the other hand, the long-range exciton diffusion in the pure NPL solids will also increase the probability of exciton trapping and further aggravate this behavior. [18] As expected, the 3-ML rich binary NPL systems,w ith much weaker exciton-phonon coupling and shorter exciton diffusion lengths,exhibit asignificant decline in the proportion of long-lived component.…”

Suppressing Strong Exciton–Phonon Coupling in Blue Perovskite Nanoplatelet Solids by Binary Systems

“…Moreover, the PL decay curves start to show a long‐lived component with the rise of temperature, which can be assigned to the phonon‐mediated recombination. On one hand, the self‐trapping exciton will not absolutely result in nonradiative decay, the trapped excitons in the band edge possibly recover to free exciton under strong phonon vibrations, thereby we can see a longer fluorescence lifetime [17] . On the other hand, the long‐range exciton diffusion in the pure NPL solids will also increase the probability of exciton trapping and further aggravate this behavior [18] .…”

“…On one hand, the self-trapping exciton will not absolutely result in nonradiative decay,the trapped excitons in the band edge possibly recover to free exciton under strong phonon vibrations,t hereby we can see alonger fluorescence lifetime. [17] On the other hand, the long-range exciton diffusion in the pure NPL solids will also increase the probability of exciton trapping and further aggravate this behavior. [18] As expected, the 3-ML rich binary NPL systems,w ith much weaker exciton-phonon coupling and shorter exciton diffusion lengths,e xhibit as ignificant decline in the proportion of long-lived component.…”