Visualization of Carrier Transport in Lateral Metal-Perovskite-Metal Structures and its Influence on Device Operation

Abstract

The high performance of hybrid perovskite-based devices is attributed to its excellent bulktransport properties. However, carrier dynamics, especially at the metal-perovskite interface, and its influence on device operation are not widely understood. This work presents the dominant transport mechanisms in methylammonium lead iodide (MAPbI3) perovskite-based asymmetric metal-electrode lateral devices. The device operation is studied with inter-electrode lengths varying from 4 μm to 120 μm. Device characteristics indicate distinct ohmic and spacecharge limited current (SCLC) regimes that are controlled by the inter-electrode length and applied bias. The electric-potential mapping using Kelvin-Probe microscopy across the device indicates minimal ion-screening effects and the presence of a transport barrier at the metal-MAPbI3 junction. Further, photocurrent imaging of the channel using near-field excitationscanning microscopy reveals dominant recombination and charge-separation zones. These lateral devices exhibit photodetector characteristics with a responsivity of about 51 mA/W in self-powered mode and 5.2 A/W at 5 V bias, in short-channel devices (4 μm). The low device capacitance enables a fast light-switching response of ~12 ns.

Modelling of Kelvin probe surface voltage and photovoltage in dielectric-semiconductor interfaces

“…The technique can be also used to measure the surface potentials of dielectrics thin films deposited on top of semiconductors, with the measured contact potential difference (CPD) being strongly dependent on the presence of charge in andon the dielectrics [5]. Thanks to these capabilities the KP method [6] has become more widespread in the photovoltaics (PV) and optoelectronics field, including the large community studying perovskite solar cells [7,8], as well as groups working on silicon devices [9][10][11][12][13][14][15], and other thin film technologies [16,17]. The working principles of KP have long been reported and used in commercial instruments.…”