Electron tunneling at the molecularly thin 2D perovskite and graphene van der Waals interface

Kai Leng,Ibrahim Abdelwahab,Peng Song,Gustavo Grinblat,Andrivo Rusydi,Runlai Li,Stefan A Maier,Yongqing Cai,Ivan Verzhbitskiy,Yan Shao,Goki Eda,Xiao Chi,Kian Ping Loh,Lin Wang,Wei Fu

doi:10.1038/s41467-020-19331-6

Abstract

Quasi-two-dimensional perovskites have emerged as a new material platform for optoelectronics on account of its intrinsic stability. A major bottleneck to device performance is the high charge injection barrier caused by organic molecular layers on its basal plane, thus the best performing device currently relies on edge contact. Herein, by leveraging on van der Waals coupling and energy level matching between two-dimensional Ruddlesden-Popper perovskite and graphene, we show that the plane-contacted perovskite and graphene interface presents a lower barrier than gold for charge injection. Electron tunneling across the interface occurs via a gate-tunable, direct tunneling-to-field emission mechanism with increasing bias, and photoinduced charge transfer occurs at femtosecond timescale (~50 fs). Field effect transistors fabricated on molecularly thin Ruddlesden-Popper perovskite using graphene contact exhibit electron mobilities ranging from 0.1 to 0.018 cm2V−1s−1 between 1.7 to 200 K. Scanning tunneling spectroscopy studies reveal layer-dependent tunneling barrier and domain size on few-layered Ruddlesden-Popper perovskite.

Highlights

Quasi-two-dimensional perovskites have emerged as a new material platform for optoelectronics on account of its intrinsic stability
The analysis reveals ultrafast injection of photo-excited carriers from G to Ruddlesden-Popper perovskites (RPPs) at timescales
Our studies show that graphene serves as a low barrier and gate-tunable van der Waals contact for n = 4 RPP where we observed the classic tunneling mechanism of field emission at high bias voltage and direct tunneling at low bias

Summary

Introduction

Quasi-two-dimensional perovskites have emerged as a new material platform for optoelectronics on account of its intrinsic stability. By leveraging on van der Waals coupling and energy level matching between two-dimensional Ruddlesden-Popper perovskite and graphene, we show that the plane-contacted perovskite and graphene interface presents a lower barrier than gold for charge injection. Field effect transistors fabricated on molecularly thin Ruddlesden-Popper perovskite using graphene contact exhibit electron mobilities ranging from 0.1 to 0.018 cm2V−1s−1 between 1.7 to 200 K. Two-dimensional (2D) Ruddlesden-Popper perovskites (RPPs) are natural quantum wells built of alternating layers of organic cations and inorganic anion cages. For RPP crystals of the stoichiometric formulae (C4H9NH3)2(CH3NH3)n−1PbnI3n+1, the presence of multiple layers of dielectrics due to (C4H9NH3)+ causes poor interlayer charge transport, field-effect transistor (FET) devices are rarely reported. Identifying an electrode material with the interface energy alignment to favor low resistance contact on 2D perovskites is needed for the fabrication of FET22. Little is known about this hybrid interface of 2D perovskite and graphene including their band alignment, the surface structure of 2D perovskites on graphene, and the dynamics of interfacial charge transfer

Methods

Results

Conclusion