SEMINARIO: Development of ZnO-polymer hybrid devices for photodiode applications

Abstract:The research on photodiodes or devices that can detect UV light, is growing rapidly due to their wide range of applications in sensors, communication devices, solar cells and radiation detection. This work focuses on the development of novel cost-effective and energy-effcient hybrid photodiodes.
These devices are composed of n-type (negative) and p-type (positive) semiconductor components that in our case, are ZnO nanorods and PEDOT:PSS / F8BT polymers, respectively. To make the fabrication cost-effective, hydrothermal synthesis was applied to grow ZnO nanorods that were then covered by polymers using spin coating. The performance of the photodiode is evaluated in terms of responsivity, sensitivity and response time. The photodiode energy efficiency was expressed through the external quantum effciency and values as high as 2770% at low bias voltage of -2V, compared to other biases were obtained. The figures of merit were assessed as a function of the ZnO-nanorod growth conditions. The first step in the synthesis of the nanorod was the deposition of the seed layer using different cost-effective and eco-friendly alcoholic solvents. The absolute methanol seed layer solvents produced the best performing photodiodes. The seed layer (nucleation layer) was further studied in order to understand the surface defects they harbor that could improve or deteriorate the performance of the final photodiode. To that end, hydrothermal synthesis was applied to produce ZnO nanoparticles with the same seeding solvents. Their size, morphology as well as chemical and physical properties were investigated and correlated to the ZnO-nanorod properties. These studies showed a direct relationship between the alcoholic solvent used during the synthesis and the defect states present in the ZnO nanostructures that control and influence the opto-electrical properties and photodiode performances. This acquired knowledge enables the further development of future cost-effective and energy-effcient photodiodes.