Excitons in ultrathin organic-inorganic perovskite crystals

Abstract

We demonstrate the formation of large sheets of layered organic-inorganic perovskite (OIPC) crystals, as thin as a single unit cell, prepared by mechanical exfoliation. The resulting 2D OIPC nano sheets of 2.4 nm thickness are direct semiconductors with an optical band gap of 2.4 eV. They exhibit unusually strong light-matter interaction with an optical absorption as high as 25% at the main excitonic resonance, as well as bright photoluminescence. We extract an exciton binding energy of 490 meV from measurement of the series of excited exciton states. The properties of the excitons are shown to be strongly influenced by the changes in the dielectric surroundings. The environmental sensitivity of these ultrathin OIPC sheets is further reflected in the strong suppression of a thermally driven phase transition present in the bulk crystals.

Two-dimensional organic-inorganic hybrid perovskite: from material properties to device applications

“…For the III-V group's semiconductor, such as heterojunction GaAs/AlAs/GaAs, excitons can only exist stably at low temperature, rather than room temperature [56]. Conversely, excitons in 2D perovskite can exist stably at room temperature due to the Cullen medium shielding effect [57]. There exists a dielectric-constant mismatch between organic layer and inorganic layer, leading to enhanced exciton effect in 2D perovskite.…”

Organic–inorganic metal halide hybrids beyond perovskites

“…Several approaches, including mechanical exfoliation [87,88], chemical vapor deposition [89], solutionprocessing [8,90,91], and colloidal methods [92] have been developed to prepare 2D perovskites. As compared to mechanical exfoliation and chemical vapor deposition techniques, solution-processing approach was more effective to achieve high-quality crystals [93].…”

Hybrid Perovskites: Effective Crystal Growth for Optoelectronic Applications

“…[26] In order to overcome the low Eb, spatial confinement via ultimate thin perovskite film sandwiched between large band-gap transport layers was used for green, red and near nm. [177] The 2D perovskite nano-sheet exhibits a strong light matter interaction with an optical absorption as high as 25% at the main excitonic resonance, as well as bright photoluminescence with an Eb of 490 meV due to the change in the dielectric environment of the ultrathin film compared to bulk. Moreover, thermal induced phase transition is suppressed in this form.…”

“…Nanostructured 3D perovskite crystals can be formed regardless of components and composition of perovskites by managing synthetic methodology. [13,177,187,189,190,[196][197][198][199] Nanostructured perovskites show further improved photoluminescence and long recombination lifetime by surface passivation effect from ligand stabilization. (Table 4) The key benefits of nanostructured perovskites are Eb increase and fast interfacial charge transport, which enables highly efficient lead halide perovskite quantum dot LEDs.…”