Functionalized Metal Oxide Semiconductor Nanorods Conducting Polymer Schottky Junctions for Photodetector Application

Abstract

Photodetectors are most important optoelectronic devices have been applied in various field of modern science such as optical communications, safety and security, astronomy, environmental sensing, medical and military devices. Photodetectors made of metal oxide semiconductor (MOS) nanostructures are particularly attractive due to fast response time, low cost synthesis process, high stability and overall environmental friendly nature. MOS/conducting polymer Schottky junction photodetectors are mostly important due to low cost, simple device geometry and compatible with flexible electronics. Recently, conducting polymer Poly 3,4-ethylenedioxythiophene: polystyrene sulfonate (PEDOT:PSS) has been studied as an alternative to metal electrodes in various optoelectronic devices due their high electrical conductivity, transparency over broad spectral range and solution deposition process. In this dissertation, Schottky junction photodetectors were fabricated with ZnO, TiO2 and CuO nanorods (NRs) and PEDOT:PSS conducting polymer junction. All nanorods were grown on fluorine doped tin oxide (FTO) coated glass substrate by hydrothermal process. The photodetector devices were fabricated by spin coating of PEDOT:PSS polymer on the top of the nanorods. The ultraviolet photodetection (UV) of ZnO/PEDOT:PSS junction was improved by using graphene quantum dots (GQDs) as a photosensitizer. The detector performance was further increased by using N doped GQDs (NGQDs). The maximum external quantum efficiency (EQE~57681%), responsivity (Rand#955;~158 A/W) and detectivity (Dand#955;~8.75×1012Hz1/2/W) was obtained in case of NGQDs sensitized device at 340 nm wavelength, under -1V bias. The enhancement of electrical conductivity of PEDOT:PSS using DMSO treatment improved the above device performance significantly (EQE~90063, Rand#955;~247A/W and Dand#955;~2.42×1011 Hz1/2/W). Dual wavelength ultraviolet-visible photosensing was studied using CdS decorated Al doped ZnO NRs. The device showed excellent dual wavelength photodetection at 380 nm and 500 nm under 0V