Correlated electron–hole plasma in organometal perovskites

Abstract

Organic-inorganic perovskites are a class of solution-processed semiconductors holding promise for the realization of low-cost efficient solar cells and on-chip lasers. Despite the recent attention they have attracted, fundamental aspects of the photophysics underlying device operation still remain elusive. Here we use photoluminescence and transmission spectroscopy to show that photoexcitations give rise to a conducting plasma of unbound but Coulomb-correlated electron-hole pairs at all excitations of interest for light-energy conversion and stimulated optical amplification. The conductive nature of the photoexcited plasma has crucial consequences for perovskite-based devices: in solar cells, it ensures efficient charge separation and ambipolar transport while, concerning lasing, it provides a low threshold for light amplification and justifies a favourable outlook for the demonstration of an electrically driven laser. We find a significant trap density, whose cross-section for carrier capture is however low, yielding a minor impact on device performance.

Temperature-dependent optical spectra of single-crystal (CH3NH3)PbBr3 cleaved in ultrahigh vacuum

“…As proposed earlier [38,39,65], we model the absorption spectra α (E) using Elliot's theory [66,67] α…”

Light-Induced Increase of Electron Diffusion Length in a p–n Junction Type CH3NH3PbBr3 Perovskite Solar Cell

“…The low exciton binding energy of the perovskite ensures that nearly all the excitons dissociate at room temperature. [16][17][18] A current collection efficiency image can be formed by synchronizing the beam position with the collected current. The current vs. position profile obtained across the junction can indicate the location of built-in fields and be used to determine carrier drift/diffusion lengths (depending on if a built-in field exists in the material or not).…”

“…The EBIC cross-section profile indicates a p-n structure between the n-FTO/TiO 2 and p-perovskite, rather than the p-i-n structure, reported for the iodide derivative. Based on the variation in space-charge region width with varying bias, measured by EBIC and capacitance-voltage measurements, we estimate the net-doping concentration in MAPbBr 3 (Cl) to be 3-6x10 17 cm -3 .…”

Triple cation mixed-halide perovskites for tunable lasers

“…The exceptional optoelectronic material properties also make them promising candidates for light emitting devices. Their superior charge carrier transport, higher index of refraction, and insensitivity of light emission on the spins of recombining charges (low triplet-exciton losses due to the dominant free carrier recombination) raise the possibility to overcome current challenges of solution processed lasers [4,5]. The more traditional materials in the field -such as conjugated polymers or colloidal quantum dots -are known for their superb color tunability and the ability for an easy integration into other devices and onto various substrates [6].…”