Band Structure Engineering of Interfacial Semiconductors Based on Atomically Thin Lead Iodide Crystals

Abstract

To explore new constituents in two-dimensional materials and to combine their best in van der Waals heterostructures, are in great demand as being unique platform to discover new physical phenomena and to design novel functionalities in interface-based devices. Herein, PbI2 crystals as thin as few-layers are first synthesized, particularly through a facile low-temperature solution approach with the crystals of large size, regular shape, different thicknesses and high-yields. As a prototypical demonstration of flexible band engineering of PbI2-based interfacial semiconductors, these PbI2 crystals are subsequently assembled with several transition metal dichalcogenide monolayers. The photoluminescence of MoS2 is strongly enhanced in MoS2/PbI2 stacks, while a dramatic photoluminescence quenching of WS2 and WSe2 is revealed in WS2/PbI2 and WSe2/PbI2 stacks. This is attributed to the effective heterojunction formation between PbI2 and these monolayers, but type I band alignment in MoS2/PbI2 stacks where fast-transferred charge carriers accumulate in MoS2 with high emission efficiency, and type II in WS2/PbI2 and WSe2/PbI2 stacks with separated electrons and holes suitable for light harvesting. Our results demonstrate that MoS2, WS2, WSe2 monolayers with very similar electronic structures themselves, show completely distinct light-matter interactions when interfacing with PbI2, providing unprecedent capabilities to engineer the device performance of two-dimensional heterostructures.Received: ((will be filled in by the editorial staff)) Revised: ((will be filled in by the editorial staff)) Published online: ((will be filled in by the editorial staff))

MoS2 and Perylene Derivative Based Type‐II Heterostructure: Bandgap Engineering and Giant Photoluminescence Enhancement

“…[17] These bands (CB and VB) are primarily responsible for band bending and charge transfer across the heterointerface to the highest-occupied-molecular-orbital/lowest unoccupied molecular orbital (HOMO/LUMO) level of the organic molecule in MoS 2 -organic heterostructures. [3,4,20] In contrast, for TMD hybrid heterostructures with a type-II (staggered) band alignment photoinduced carriers can transfer through the interface and be separated at different material due to the large band offsets. [18,19] Generally, in the case of type-I (normal) band edge alignment, the photogenerated electrons and holes can efficiently transfer from wider bandgap material to the narrower bandgap material, leading to an increased carrier population and enhanced PL emission, which has the potential for light-emitting applications.…”

“…As a result, PL behavior of MoS 2 can be significantly tailored. [6,21,22] To our knowledge, the enhanced PL emission of TMDs could be achieved with the combination of organic semiconductors, such as pentacene, [3] perylene tetracarboxylic dianhydride, [23] titanyl phthalocyanine, [24] and inorganic materials such as lead iodide, [4] ZnO nanorods, [25] 2D layer (BN, MoTe 2 ), [26,27] and metal nanoparticles, [28,29] via charge carrier/energy transfer, strain relaxation, and surface plasmon effects. [3,4,20] In contrast, for TMD hybrid heterostructures with a type-II (staggered) band alignment photoinduced carriers can transfer through the interface and be separated at different material due to the large band offsets.…”

Engineering the Phases and Heterostructures of Ultrathin Hybrid Perovskite Nanosheets

“…Synthesis: The PbI 2 nanosheets are synthesized by a previouslyreported solution method. [23] For the synthesis of MAPbI 3 nanosheets, MAI powder is put in the upstream heating zone of the tube. An evaporation temperature of 115 °C is applied for 100 min and the growth temperature of the perovskite crystals is maintained at 90 °C for 200 min.…”

“…This method has the advantages of a simple operation, high yields and mild environmental conditions, which allows us to obtain in abundance PbI 2 nanosheets of various thicknesses, which have a trigonal/hexagonal shape. [23][24] As a second step, we then apply a CVD procedure to these PbI 2 nanosheets by exposing them to AI vapor (A + is MA + or FA + ), which results in the formation of APbI 3 perovskite nanosheets. A more detailed description of our approach can be found in the Experimental Section.…”

Surface group-modified MXene nano-flake doping of monolayer tungsten disulfides

“…[12][13][14][15] Several strategies were attempted to introduce p-type doping to modulate the electronic property of monolayer TMDCs, thus resulting in the enhancement of radiative recombination. [16][17][18][19] Such strategies, including substitutional doping during growth, 16 back gate or top liquid gate, 20 vertical heterostructure and/or gas molecule adsorption, 21,22 and band structure engineering, 23 had been applied for manipulating the carrier concentrations in monolayer TMDCs. Nevertheless, the requirement for complicated and precise technological processes is the main hindrance to obtain the desired optoelectronic properties of monolayer TMDCs, which becomes a great limitation to the fundamental study of monolayer TMDCs.…”