High On/Off Ratio Devices with Broadband Photoresponse based on Surface Functionalized and Defect Controlled Optoelectronic Materials

Abstract

Photodetectors, which convert optical signals into electrical signals, are essential components for various fields. Recently, broadband photodetection from ultraviolet (UV) to near infrared (NIR) become central to modern science and technology, as the light with a wavelength of 400 nm to 1000 nm has notable advantages such as harmless characteristics, free frequency usage fee, high transmission rate, and high transmission capacity. However, it is difficult to develop high performance broadband photodetectors due to the lack of proper materials which have the ability to absorb of incident radiation over broad wavelength range with excellent optoelectronic transfer efficiency and high reliability. In this respect, careful investigation of methods for how materials can show high on/off ratio under the wide range of wavelength should be carried out for developing high performance broadband photodetector. Therefore, this study focuses on design of high on/off ratio devices with broadband photodetection from UV to NIR to develop high performance and reliable broadband photodetectors. <br/> By surface functionalization, Ag-decorated vanadium dioxide (VO2) nanorod arrays (NRs)-based broadband photodetector are realized experimentally. Efficient broadband photodetection via localized surface plasmon resonance (LSPR) assisted photo-induced metal-insulator transition (MIT) occurs in Ag-decorated VO2 NRs. The porous nanostructure can enable VO2 to have a high specific area to be illuminated and to be well-decorated with Ag nanoparticles along the whole surface. Due to LSPR, strong electromagnetic coupling, which occurs at the interface between Ag nanoparticles and VO2 NRs, provokes daylight-induced MIT in VO2. MIT-driven broadband photodetection with the high response has not been observed in bare VO2 dense planar thin films and this will open up the new strategy for a new functionalization in strongly correlated materials. <br/> By controlling of defect migration, reliable high On/Off ratio (Ion/Ioff = 104) CH3NH3PbI3 broadband photodetectors with transport layer-free simple metal/semiconductor/metal lateral structure are demonstrated. At high external bias, low On/Off ratios and spikes in dark current and photocurrent are observed due to the charged defect migration. The charged defect migration can be effectively inhibited at low external bias, and thus the CH3NH3PbI3-based photodetectors show high Ion/Ioff ratios and spike-free dark current and photocurrent. In addition, prevention of the prepoling in the CH3NH3PbI3 films by operating at the low external bias results in pronouncedly enhanced signal-to-noise ratios even under low intensity incident light. These results strongly propose that inhibiting the migration of charged defect ions in CH3NH3PbI3 films is a key in developing reliable high performance CH3NH3PbI3-based devices.<br/> Our approaches to enhance broadband photodetection performance of devices will open up the way to future devices. This study serves as a valuable proof-of-concept for next generation optoelectronic devices with fast response, low power consumption, high performance. and high relibility.<br/>