Vapor Phase Selective Growth of Two-Dimensional Perovskite/WS₂ Heterostructures for Optoelectronic Applications

Abstract

Organic–inorganic hybrid perovskites have attracted increased interest owing to their exceptional optoelectronic properties and promising applications. Monolayers of transition metal dichalcogenides (TMDCs), such as tungsten disulfide (WS2), are also intriguing because of their unique optoelectronic properties and their atomically thin and flexible structures. Therefore, the combination of these different types of materials is very attractive in terms of fundamental science of interface interaction, as well as for the realization of ultrathin optoelectronic devices with high performance. Here, we demonstrate the controlled synthesis of two-dimensional (2D) perovskite/WS2 heterostructures by an all vapor-phase growth approach. This involves the chemical vapor deposition (CVD) growth of monolayer WS2, followed by the vapor-phase selective deposition of 2D PbI2 onto the WS2 with the successive conversion of PbI2 to organic–inorganic perovskite (CH3NH3PbI3). Moreover, the selective growth of the perovskite on prepatterned WS2 enables the direct synthesis of patterned heterostructures, avoiding any damage to the perovskite. The photodetectors utilizing the perovskite/WS2 heterostructure show increased responsivities compared with isolated thin perovskite obtained by conventional solution methods. The integration of 2D perovskite with TMDCs opens a new avenue to fabricate advanced devices by combining their unique properties and overcoming current processing difficulties of perovskites.

Type-I Heterostructure and Improved Phase Stability of Formamidinium Lead Iodide Perovskite Grown on WS_2

“…Previously, we reported this unique selective growth behavior for MAPbI3 perovskite/WS2 heterostructures. 17) Our analyses revealed that the higher surface energy of WS2 compared to c-plane sapphire assists the growth of 2D perovskite layer 17) . As the selective growth takes place during the deposition of the PbI2 layer, we observe a similar growth behavior in FAPbI3.…”

“…In contrast, the PL from WS2 was strongly quenched. According to the band structure calculations, the heterostructure of FAPbI3 and WS2 possesses type-I band alignment 17,[24][25][26] . The type-I band alignment is displayed in Fig.…”

“…However, in our case the bandgap increased to 1.61 eV as can be seen in the blue shifted PL emission. This blue shift can be explained by the quantum confinement effect in 2D FAPbI3 due to the reduced thickness 17,23) . Absorption spectrum of the heterostructure (blue data in Fig 1e) agrees well with the PL spectrum.…”

“…The WO3, sulfur, and substrates were heated at 1065 °C, 165 °C, and 925 °C, respectively. This as-grown WS2/sapphire substrate was subjected to the following two-step process 17) to synthesize FAPbI3 perovskite layer on the WS2 surface. First step was the vapor-deposition of PbI2 on WS2.…”

“…These heterostructures exhibited improved performances in device applications and novel properties. Very recently, we demonstrated a perovskite/TMDC heterostructure with type-II band alignment 17) . In type-II heterostructures, electrons and holes are separated into different layers due to the staggered alignment of valance and conduction bands of each layer.…”