Reconfiguring band-edge states and charge distribution of organic semiconductor–incorporated 2D perovskites via pressure gating

Abstract

Two-dimensional (2D) semiconductor heterostructures are key building blocks for many electronic and optoelectronic devices. Reconfiguring the band-edge states and modulating their interplay with charge carriers at the interface in a continuous manner have long been sought yet are challenging. Here, using organic semiconductor–incorporated 2D halide perovskites as the model system, we realize the manipulation of band-edge states and charge distribution via mechanical—rather than chemical or thermal—regulation. Compression induces band-alignment switching and charge redistribution due to the different pressure responses of organic and inorganic building blocks, giving controllable emission properties of 2D perovskites. We propose and demonstrate a “pressure gating” strategy that enables the control of multiple emission states within a single material. We also reveal that band-alignment transition at the organic-inorganic interface is intrinsically not well resolved at room temperature owing to the thermally activated transfer and shuffling of band-edge carriers. This work provides important fundamental insights into the energetics and carrier dynamics of hybrid semiconductor heterostructures.

Spacer-Dependent and Pressure-Tuned Structures and Optoelectronic Properties of 2D Hybrid Halide Perovskites

“…For example, the PMA and PEA spacer cations differ only by a CH 2 group, yet the high-pressure behaviors of (PMA) 2 PbI 4 and (PEA) 2 PbI 4 are drastically different. PMA 2 PbI 4 exhibits the largest bandgap narrowing by 0.89 eV upon compression, whereas the bandgap of PEA 2 PbI 4 only exhibits a maximum reduction of 0.43 eV upon slight compression before increasing again and becoming indirect at higher pressures. , In addition, many organic materials exhibit pressure-induced bandgap narrowing; however, the organic spacer cations in different perovskite matrices not only shift the bandgap energy but also exhibit drastically different pressure-tuned behaviors. Therefore, the important and distinctive role organic cations play in the pressure-tuned optoelectronic properties calls for more in-depth studies.…”

“…The mechanical compression of perovskites can result in modification of the Pb–X bond lengths and angles in the inorganic lattice. The subsequent change in orbital overlap results in modification of the observed optoelectronic properties. − The effects of high pressure on 3D HOIPs, such as MAPbI 3 and FAPbI 3 , have been studied extensively. − More recently, high-pressure studies have been conducted on 2D lead-halide-based HOIPs, mostly focused on those with BA (butylammonium), PMA (phenyl methylammonium), or PEA (phenyl ethylammonium) spacer cations. − However, the effects of different spacer cations on the pressure-tuned optoelectronic properties are still not well understood. For example, the PMA and PEA spacer cations differ only by a CH 2 group, yet the high-pressure behaviors of (PMA) 2 PbI 4 and (PEA) 2 PbI 4 are drastically different.…”

Light-Emitting Organic Semiconductor-Incorporated Perovskites: Fundamental Properties and Device Applications

“…(E) Band alignment switching in response to pressure. Reproduced with permission from ref . Copyright 2022 AAAS.…”

Bandgap narrowing and piezochromism of doped two-dimensional hybrid perovskite nanocrystals under pressure

“…Using pressure, Lv et al achieved a near 100% PLQY in one-dimensional (1D) hybrid metal halides, and unraveled the underlying mechanisms of pressure gating. 22,23 Moreover, through changing the structure with pressure, Zou et al promoted a non-luminescent material to exhibit emission and retained the strong emission under ambient conditions, as well as reducing the bandgap to achieve perovskite metallization, etc. [24][25][26][27][28][29] Doping Mn 2+ combined with pressure will shorten the distance between molecules and amplify deformation of the octahedral framework, thus directly enhancing the photoelectric characteristics.…”