Francis Otieno

Maseno University · Department of Physics and Materials Science

Herein, we report on the synthesis of InSe nanosheets. We further report on the interdependency of concentration and time on the evolution of the nanosheets as well as the role of the capping agents on the crystal phase and morphology of the resultant particles. Our results show that hexagonal like InSe nanosheets were synthesized at different opti...

Spin coaters offer an invaluable method of thin film fabrication. Various implementations, both proprietary and open-source exist, offering vacuum and gravity samples chucks. These implementations vary in their reliability, ease-of-use, cost, and versatility. Here we present a novel easy-to-use open-source gravity-chuck type spin coater with minima...

Indium selenide is currently receiving tremendous attention in device application and studies related to two dimensional nanostructured technologies. Non-layered γ-In2Se3, which is a stable phase at room temperature, was successfully synthesized in oleylamine after 10 min at 240 °C from InCl3 and elemental selenium. Prolonged reaction time resulted...

The colloidal synthesis of Cu2ZnSnS4 (CZTS) and Cu2ZnSnSe4 (CZTSe) nanoparticles and their application as counter electrodes in dye-sensitized solar cells (DSSCs). In particular, the effect of three substrates namely; vitreous carbon (VC), indium tin oxide (ITO), and fluorine doped tin oxide (FTO) on the electrocatalytic properties as well as the o...

Ag nanoparticles (NPs) of varied concentrations are implemented in the hole transport layer (PEDOT:PSS) of organic solar cells to enhance the photoconversion efficiency through near field effects, one of the basis of surface plasmonic resonances. The Ag NPs were synthesized through a wet chemistry reduction process by varying the reaction times to...

Fundamentally, organic solar cells (OSCs) with a bulk-heterojunction active layer are made of at least two electronically dissimilar molecules, in which photoabsorption in one (donor) generates Frenkel excitons. The formation of free charge carriers emerge after exciton dissociation at the donor:acceptor interface. In the past decade, most of the p...

A major noble way to realizing high-efficiency organic solar cell device is the use of ternary blends with non-fullerene acceptors. Although offset in the band gap (E-gap) of the donor/acceptor material is negligible, it still exhibits ultra-fast and efficient charge separation. Regardless of the progress made, device optimization and fundamental u...

2D hybrid perovskites are promising materials for solar cell applications, in particular, cesium based perovskite nanocrystals as they offer the stability that is absent in organic-inorganic perovskite. However, the most...

Nickel selenide (Ni x Se y) systems have received much attention in recent years as potential low cost counter electrodes (CEs) in dye sensitized solar cells (DSSCs). Their electrocatalytic activities are comparable to that of the conventional platinum CE. Despite their achievements, the effect of stoichiometry on their catalytic performance as CEs...

Eu-doped ZnO (ZnO:Eu³⁺) thin films deposited by RF magnetron sputtering have been investigated to establish the effect of annealing on the red photoluminescence. PL spectra analysis reveal a correlation between the characteristics of the red photoluminescence and the annealing temperature, suggesting efficient energy transfer from the ZnO host to t...

We report an investigation on the effect of oxygen flow rate on the structural and optical properties of zinc oxide thin films prepared by RF magnetron sputtering. The structural measurements were carried using grazing incidence X-ray diffraction, atomic force microscopy and Raman spectroscopy. The role of oxygen partial pressure on the crystallini...

The effects of implantation of Samarium ions (Sm⁺), a rare earth ion (RE) on the properties of ZnO films grown on Si (001) substrate by RF sputtering system are presented. The structural properties of the virgin and Sm–implanted ZnO thin films were investigated by Atomic force microscopy, Rutherford backscattering spectroscopy and Raman spectroscop...

Down conversion has been applied to minimize thermalization losses in photovoltaic devices. In this study, terbium-doped ZnO (ZnO:Tb³⁺) thin films were deposited on ITO-coated glass, quartz and silicon substrates using the RF magnetron sputtering technique fitted with a high-purity (99.99%) Tb³⁺-doped ZnO target (97% ZnO, 3% Tb) for use in organic...

Aluminium doped zinc oxide thin films are prepared by Radio Frequency magnetron sputtering in pure argon atmosphere at 100 W. The structural results reveal good film adhesion on a silicon substrate (001). The thin films were then subjected to heat treatment in a furnace under ambient air. The structural, morphological, and optical properties of the...

Au based plasmonic phenomenon inside the hole transport layer poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT:PSS) of an organic solar cell based on blend of poly(3-hexylthiophene) (P3HT) and [6:6]-phenyl-C61-butyric acid (PCBM) is investigated. The concentration of the Au nanoparticles synthesized by wet chemical reduction is one of...

The efficiency of bulk heterojunction organic photovoltaic cells can be enhanced through heat treatment of the components of the blend solution. The morphology of films spun from the heat treated blend solution reveals a more favorable diffusion of [6,6]-phenyl-C61-butyric acid methyl ester into the Poly(3-hexylthiophene-2,5-diyl) matrix than obser...

In the present work we compare the performance of a pristine P3HT:PCBM based bulk heterojunction solar cell with a device incorporated with pentacene encapsulated Ag nanoparticles. Encapsulation has been achieved through thermal evaporation of a 22 nm pentacene thin film. Introduction of pristine Ag nanoparticles revealed better overall performance...

Herein we report for the first time, on the synthesis and characterization of indium monoselenide nanoparticles and nanosheets and their application as chemical sensors. We investigate the effect of the different morphologies on methanol and formaldehyde sensing. The synthesized nanostructures crystallized in the same phase however the different mo...