School of Chemistry & Physics

Dr Jude Ike waits to be awarded his doctoral degree in Physics.

Metal Nanoparticles Used to Harness Solar Radiation in Physics Research

Nigerian national Dr Jude Ike graduated with a PhD degree in Physics, focusing his research on the use of metal nanoparticles as a mechanism to harness solar radiation, using a thin film polymer medium.

Supervisor Professor Genene Mola explained that Ike had found new evidences on the effect of plasmonic phenomenon on the collection of enhanced photogenerated currents in polymer solar cells. Consequently, four research articles have been published in well-known international scientific journals.

Ike thanked Mola and UKZN for providing a supportive environment that facilitated the smooth execution of his research project.

‘There is a growing focus among researchers on metal plasmonic as a mechanism to improve the performance of thin film organic solar cells (TFOSCs) based on organic materials, which are noted for their low device fabrication costs, flexibility, portability and lightweight,’ said Ike.

‘These devices utilise conjugated polymer materials as electron-donating agents, and fullerene-based derivative materials as electron acceptors.

‘Although the advantages highlighted are considerable, TFOSCs commercialisation has been hindered by their inferior power conversion efficiency (PCE) compared to traditional inorganic solar cells,’ he said. ‘The PCE of TFOSCs is limited by the low electrical conductivity, charge mobility and light absorption range of most organic materials. Furthermore, the susceptibility of organic materials-based solar cell devices to degradation due to environmental exposure and photo-oxidation induced by light illumination cannot be overlooked.

‘The fundamental structure of conventional TFOSCs is composed of two primary layers, namely the photoactive layer and the charge transport buffer layer,’ said Ike. ‘To achieve maximum PCE in TFOSCs, the photoactive layer should exhibit excellent exciton generation with high optical absorption and efficient charge mobility to prevent recombination during carrier transport to the electrodes.

‘Achieving high electrical conductivity with selective charge retention and precise bandgap alignment within the charge transport layer is vital for maximising the durability of unfettered charge carriers.’

Ike said that an encouraging avenue for addressing the constraints of TFOSCs involved the integration of metal nanoparticles (NPs) and graphene.

‘In recent years, metallic nanoparticles (NPs) have been introduced into solar cells to increase photon harvesting using the localised surface plasmonic resonance (LSPR) of metallic NPs while keeping the active layer thin,’ he said. ‘The bimetallic nanoparticles (BMNPs) may be easier and cheaper to fabricate, or exhibit a higher performance compared to dielectric light scattering approaches.

‘When incorporated close to the interface between the photoactive and hole transport layers, the NPs lead to concentrated optical electric fields near the junction, which enhances exciton creation within an exciton diffusion length away from the active layer medium.

‘In light of this, incorporation of BMNPs in the photoactive and hole transport layers, is aimed at improving the photons absorption either by LSPR effect or by way of near and far field scattering, which grows the optical path length within a photoactive medium,’ he said.

Ike explained the motivation for his research: ‘As time continues, the human race is predicted to require twice as much energy as is currently being consumed, underscoring the importance of responsible energy management and conservation.

‘The use of fossil fuels as an energy source is paving the way for severe risk of global warming, with devastating consequences. The solution to this problem stands out as truly desirable: harnessing renewable energy offers numerous benefits, from reducing costs and boosting the efficacy of solar cells to promoting environmental stability, inspiring global action against climate change, and prompting entrepreneurial innovation.

‘In addition, the use of organic photovoltaic cells has enormous potential to enhance the integration of renewable energy sources, owing to their notable advantages, including possible solution processability on flexible substrates and plenty of surface area suitable for large-scale applications.’

Ike, who has set his sights on postdoctoral research, thanked God for giving him the opportunity to complete his PhD in the field of Material Science in Physics.

‘Moving forward, my intention is to work much harder than ever before.’

Words: Sally Frost

Photograph: Albert Hirasen