Direct Observation of Perovskite Photodetector Performance Enhancement by Atomically Thin Interface Engineering

Abstract

Lead trihalide perovskites have been integrated with atomically thin WS2 and served as absorption layers to improve photoresponsivity in photodetectors. The combination of perovskites and two-dimensional (2D) transition-metal dichalcogenide (TMDC) materials provides the platform to study light–matter interactions and charge transfer mechanisms in optoelectronic devices. Herein, conductive and photoconductive atomic force microscopy were used to image the dark current and photocurrent generated in WS2/CH3NH3PbI3 (MAPbI3) heterostructures. Dark current measurement in the applied voltage range displays characteristic diode behavior, which can be well described by thermionic emission theory. Under laser illumination at 532 nm, the spatially resolved photocurrent images exhibit location-dependent photoresponse, where the photocurrent increases remarkably for the WS2/MAPbI3 heterostructures compared with the bare MAPbI3 regions. Furthermore, comparative surface roughness and 2D Fourier analysis of the topographic and current maps reveal that the interfacial conditions of the WS2/MAPbI3 heterojunctions play an important role in the charge separation process. In addition, WS2/MAPbI3-based photodetectors have been fabricated. Our study provides direct evidence that atomically thin TMDC monolayers can effectively assist the charge separation process and improve the light-to-electric energy conversion, which aids in the design principles and understanding of 2D heterostructured optoelectronic devices.

Self-Powered Perovskite/CdS Heterostructure Photodetectors

“…X-ray diffraction (XRD) measurements were also performed and provided further evidence of the presence of the CdS and MAPbI3 when deposited on ITO ( Figure 1c). The diffraction peaks of CdS indium tin oxide (ITO) (transparent electrode), 28 and MAPbI3. 42,43 are indicated by the yellow, green and blue bars, 41 respectively.…”

“…The relatively high η is likely attributable to non-idealities such as defects at the perovskite surface. 28 Figure 7d were also studied by PC-AFM in order to compare the charge transport with photocurrent characteristics. Figure S12 shows the photocurrent maps obtained at different applied sample potentials measured under 405 nm laser illumination.…”

“…[21][22][23][24][25][26][27] Moreover, the existence of a built-in potential at the heterointerface is desirable as it can effectively suppress the carrier recombination. 28 Therefore, identifying suitable ETL systems is important for improving the performance of both solar cells and photodetectors. To this end, CdS is a well studied n-type semiconductor for solar cells and photodetectors with suitable energy band structure aligned with CH3NH3PbI3 (MAPbI3).…”

High-Performance Photoresistors Based on Perovskite Thin Film with a High PbI2 Doping Level

“…The PC-AFM measurements are conducted using a Pt-Ir-coated conductive AFM tip. Bias voltages are applied on the conductive ITO substrate and the Pt-Ir tip is held at ground [49]. For the PC-AFM technique, topography and photocurrent of MAPbI 3 can be recorded simultaneously.…”

“…Responsivity ( R ) is an important parameter to assess the performance of a photodetector. R can be calculated using the following equation: R=Ip−IdPA where I p , I d , P , and A are the photocurrent, dark current, incident light intensity, and active area of the device, respectively [49]. The responsivities of all devices at a 5 V bias voltage are summarized in Table 2.…”