The band alignment of CH3NH3PbI3/MoS2 and CH3NH3PbI3/WSe2 heterojunction.

Guan-Hao Chen^1*, Chia-Shuo Li², Li-Syuan Lu¹, Kai-Cheng Wang³, Han Yeh¹, Hung-Ru Hsu³, Chih-I Wu², Wen-Hao Chang¹

¹Department of Electrophysics, National Chiao Tung University, Hsinchu, Taiwan
²Graduate Institute of Photonics and Optoelectronics, National Taiwan University, Taipei, Taiwan
³Green Energy and Environment Research Laboratories, Industrial Technology Research Institute, Hsinchu, Taiwan

* Presenter:Guan-Hao Chen, email:a0913635603@gmail.com

The performance of a solar cell device strongly depends on the light trapping characteristics of the absorption layer as well as the charge separation at the donor/acceptor interfaces. Halide perovskite is an organometallic halide with a calcium titanate (CaTiO3) structure. In terms of material properties, the energy gap of perovskite material can be controlled by changing the composition. Perovskite has good light harvest characteristics such as low carrier recombination rate and long carrier diffusion length, which is very suitable for solar cell applications. On the other hand, Transition Metal Dichalcogenides (TMDC) is an atomically thin two-dimensional material which exhibit strong light-matter interaction, large optical conductivity and high electron mobility. Thus they are promising candidates for next-generation ultrathin solar cells. In this work, we demonstrate the band offset at the CH3NH3PbI3/MoS2 and CH3NH3PbI3/WSe2 interface. We found that the perovskite photoluminescence is quenched by the presence of TMDC, with a quenching ratio of 10 (103) for MoS2 and (WSe2). The Ultraviolet Photoelectron Spectroscopy measurements show that both the band alignments of CH3NH3PbI3/MoS2 and CH3NH3PbI3/WSe2 are type-II, indicating that MoS2 and WSe2 can act as an electron transport layer and hole transport layer, respectively.

Keywords: Band alignment, Heterojunction, Perovskite, Charge transfer, Two dimensional material