Self‐Assembled Perovskite Nanoislands on CH₃NH₃PbI₃ Cuboid Single Crystals by Energetic Surface Engineering

Abstract

Organometal perovskite single crystals have been recognized as a promising platform for high-performance optoelectronic devices, featuring high crystallinity and stability. However, a high trap density and structural nonuniformity at the surface have been major barriers to the progress of single crystal-based optoelectronic devices. Here, the formation of a unique nanoisland structure is reported at the surface of the facet-controlled cuboid MAPbI 3 (MA = CH 3 NH 3 +) single crystals through a cation interdiffusion process enabled by energetically vaporized CsI. The interdiffusion of mobile ions between the bulk and the surface is triggered by thermally activated CsI vapor, which reconstructs the surface that is rich in MA and CsI with reduced dangling bonds. Simultaneously, an array of Cs-Pb-rich nanoislands is constructed on the surface of the MAPbI 3 single crystals. This newly reconstructed nanoisland surface enhances the light absorbance over 50% and increases the charge carrier mobility from 56 to 93 cm 2 V −1 s −1 . As confirmed by Kelvin probe force microscopy, the nanoislands form a gradient band bending that prevents recombination of excess carriers, and thus, enhances lateral carrier transport properties. This unique engineering of the single crystal surface provides a pathway towards developing high-quality perovskite single-crystal surface for optoelectronic applications.

Controllable Acceleration and Deceleration of Charge Carrier Transport in Metal‐Halide Perovskite Single‐Crystal by Cs‐Cation Induced Bandgap Engineering

“…[28] The sum-of-mobilities of electron and hole (Σµ) is determined to be 56, 66, and 93 cm 2 V −1 s −1 for bare, 25CsI, and 65CsI samples, respectively. [29] This indicates up to 66% improvement in the Σµ of the 65CsI sample compared with that of the bare sample, which consistently supports an acceleration (65CsI) of the carrier transport, while the slightly increased mobility in the 25CsI sample can be ascribed to the combination of the surface/defect passivation and the formation of an energy barrier at the transition layer due to the abrupt Cs-concentration and bandgap change.…”

Overcoming the limitations of low-bandgap Cu2ZnSn(S,Se)4devices under indoor light conditions: from design to prototype IoT application

“…The CPD is measured as the difference in the work function between the sample and the tip, where the work function of the used tip is −4.93 eV. 53 Accordingly, the work functions of CZTSSe and CZTSSe:Ag–Ge are calculated, which were found to be around −4.39 and −4.55 eV, respectively. This implies that the work function of the CZTSSe:Ag–Ge sample reduces after co-doping Ag–Ge in the CZTSSe absorber layer.…”

Challenges in the development of metal-halide perovskite single crystal solar cells

“…5a). 145 Simultaneously, a mixed-cation composition of MA x Cs 1−x PbI 3 is formed near the surface that is benecial to reconstructing the ununiform crystal surface of the host MAPbI 3 SC. This passivation technique by optimizing the composition and morphology of the surface region conrms the signicantly enhanced carrier transport by increasing the carrier mobility from 56 cm 2 V −1 s −1 to 93 cm 2 V −1 s −1 .…”