Department of Physics

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Browsing Department of Physics by Author "Jhamba, L."

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    Metal oxide nanostructures and hybrid perovskite semiconductor for photovoltaic application
    (2020-02) Olaleru, Solomon Alan; Kirui, J. K.; Jhamba, L.; Wamwangi, D.; Roro, K.
    Perovskite-based solar cells (PSC) is the fastest growing solar technology to date since inception in 2009. This technology has invigorated the photovoltaic (PV) community. While it has taken 15-42 years for traditional PV technologies to achieve maturity, PSC technology has accomplished the same within 10 years. As of late, hybrid perovskite materials have shown incredible possibilities for solar energy conversion and optoelectronics technologies by virtue of its benefits of high conversion efficiency, low-cost preparation and the application of earthabundant materials, which are basic determinants for massive production. The optical properties of lead halide perovskites are of basic significance for almost all applications. Based on the screening from literature, the greater part of reports centred on the fabrication of photovoltaic devices, while the photophysical processes of these materials are missing. In this work, we reported the photophysics of halide perovskites from materials to device. The charge dynamics and charge transport mechanisms were also investigated. At first, we optimized the properties of the perovskite materials before fabrication so as to identify optimal conditions for chemical and material synthesis. These optimal conditions of base perovskite preparations necessitated the use of powder samples to form single phases and also to determine the kinetics and energetics of phase formation. We explored the impact of antisolvent and additive on the photophysical properties and a better understanding of optical response of the perovskite materials. We hold the view that the performance improvement focused on material quality alone without complete understanding of the physics of the carrier-light interaction will not provide adequate solutions to existing problems. We used DMSO as an additive in DMF to regulate the crystal growth by dissolving the residue of PbI2 which can impede the crystallization and ethyl acetate as an anti-solvent to control the morphology of the perovskite film resulting in improved homogeneity. Their impacts on optical properties were examined along with consequent improvement on the light absorption property. Herein, we reported the charge transport mechanism and recombination phenomena in dopantfree HTM perovskite solar cell using I-V and EIS measurement with the focus on physical processes within the perovskite material as an active layer and the parameters that determine the photovoltaic performance. Impedance spectroscopy technique, which reveals the various interfacial processes in terms of resistive and capacitive elements, is used to get an insight into the charge transport through the junction and bulk of the FTO-perovskite solar cell. Again these values were consistent with the results obtained from I-V analysis. These analyses of current– voltage (I–V) characteristics and impedance spectroscopy technique provide essential insights into the performance parameters which determine the transport mechanism and location of electron hole recombination and the efficiency of the device. Perovskite-based solar cells (PSC) is the fastest growing solar technology to date since inception in 2009. This technology has invigorated the photovoltaic (PV) community. While it has taken 15-42 years for traditional PV technologies to achieve maturity, PSC technology has accomplished the same within 10 years. As of late, hybrid perovskite materials have shown incredible possibilities for solar energy conversion and optoelectronics technologies by virtue of its benefits of high conversion efficiency, low-cost preparation and the application of earthabundant materials, which are basic determinants for massive production. The optical properties of lead halide perovskites are of basic significance for almost all applications. Based on the screening from literature, the greater part of reports centred on the fabrication of photovoltaic devices, while the photophysical processes of these materials are missing. In this work, we reported the photophysics of halide perovskites from materials to device. The charge dynamics and charge transport mechanisms were also investigated. At first, we optimized the properties of the perovskite materials before fabrication so as to identify optimal conditions for chemical and material synthesis. These optimal conditions of base perovskite preparations necessitated the use of powder samples to form single phases and also to determine the kinetics and energetics of phase formation. We explored the impact of antisolvent and additive on the photophysical properties and a better understanding of optical response of the perovskite materials. We hold the view that the performance improvement focused on material quality alone without complete understanding of the physics of the carrier-light interaction will not provide adequate solutions to existing problems. We used DMSO as an additive in DMF to regulate the crystal growth by dissolving the residue of PbI2 which can impede the crystallization and ethyl acetate as an anti-solvent to control the morphology of the perovskite film resulting in improved homogeneity. Their impacts on optical properties were examined along with consequent improvement on the light absorption property. Herein, we reported the charge transport mechanism and recombination phenomena in dopantfree HTM perovskite solar cell using I-V and EIS measurement with the focus on physical processes within the perovskite material as an active layer and the parameters that determine the photovoltaic performance. Impedance spectroscopy technique, which reveals the various interfacial processes in terms of resistive and capacitive elements, is used to get an insight into the charge transport through the junction and bulk of the FTO-perovskite solar cell. Again these values were consistent with the results obtained from I-V analysis. These analyses of current– voltage (I–V) characteristics and impedance spectroscopy technique provide essential insights into the performance parameters which determine the transport mechanism and location of electron hole recombination and the efficiency of the device. Perovskite-based solar cells (PSC) is the fastest growing solar technology to date since inception in 2009. This technology has invigorated the photovoltaic (PV) community. While it has taken 15-42 years for traditional PV technologies to achieve maturity, PSC technology has accomplished the same within 10 years. As of late, hybrid perovskite materials have shown incredible possibilities for solar energy conversion and optoelectronics technologies by virtue of its benefits of high conversion efficiency, low-cost preparation and the application of earthabundant materials, which are basic determinants for massive production. The optical properties of lead halide perovskites are of basic significance for almost all applications. Based on the screening from literature, the greater part of reports centred on the fabrication of photovoltaic devices, while the photophysical processes of these materials are missing. In this work, we reported the photophysics of halide perovskites from materials to device. The charge dynamics and charge transport mechanisms were also investigated. At first, we optimized the properties of the perovskite materials before fabrication so as to identify optimal conditions for chemical and material synthesis. These optimal conditions of base perovskite preparations necessitated the use of powder samples to form single phases and also to determine the kinetics and energetics of phase formation. We explored the impact of antisolvent and additive on the photophysical properties and a better understanding of optical response of the perovskite materials. We hold the view that the performance improvement focused on material quality alone without complete understanding of the physics of the carrier-light interaction will not provide adequate solutions to existing problems. We used DMSO as an additive in DMF to regulate the crystal growth by dissolving the residue of PbI2 which can impede the crystallization and ethyl acetate as an anti-solvent to control the morphology of the perovskite film resulting in improved homogeneity. Their impacts on optical properties were examined along with consequent improvement on the light absorption property. Herein, we reported the charge transport mechanism and recombination phenomena in dopantfree HTM perovskite solar cell using I-V and EIS measurement with the focus on physical processes within the perovskite material as an active layer and the parameters that determine the photovoltaic performance. Impedance spectroscopy technique, which reveals the various interfacial processes in terms of resistive and capacitive elements, is used to get an insight into the charge transport through the junction and bulk of the FTO-perovskite solar cell. Again these values were consistent with the results obtained from I-V analysis. These analyses of current– voltage (I–V) characteristics and impedance spectroscopy technique provide essential insights into the performance parameters which determine the transport mechanism and location of electron hole recombination and the efficiency of the device. Perovskite-based solar cells (PSC) is the fastest growing solar technology to date since inception in 2009. This technology has invigorated the photovoltaic (PV) community. While it has taken 15-42 years for traditional PV technologies to achieve maturity, PSC technology has accomplished the same within 10 years. As of late, hybrid perovskite materials have shown incredible possibilities for solar energy conversion and optoelectronics technologies by virtue of its benefits of high conversion efficiency, low-cost preparation and the application of earthabundant materials, which are basic determinants for massive production. The optical properties of lead halide perovskites are of basic significance for almost all applications. Based on the screening from literature, the greater part of reports centred on the fabrication of photovoltaic devices, while the photophysical processes of these materials are missing. In this work, we reported the photophysics of halide perovskites from materials to device. The charge dynamics and charge transport mechanisms were also investigated. At first, we optimized the properties of the perovskite materials before fabrication so as to identify optimal conditions for chemical and material synthesis. These optimal conditions of base perovskite preparations necessitated the use of powder samples to form single phases and also to determine the kinetics and energetics of phase formation. We explored the impact of antisolvent and additive on the photophysical properties and a better understanding of optical response of the perovskite materials. We hold the view that the performance improvement focused on material quality alone without complete understanding of the physics of the carrier-light interaction will not provide adequate solutions to existing problems. We used DMSO as an additive in DMF to regulate the crystal growth by dissolving the residue of PbI2 which can impede the crystallization and ethyl acetate as an anti-solvent to control the morphology of the perovskite film resulting in improved homogeneity. Their impacts on optical properties were examined along with consequent improvement on the light absorption property. Herein, we reported the charge transport mechanism and recombination phenomena in dopantfree HTM perovskite solar cell using I-V and EIS measurement with the focus on physical processes within the perovskite material as an active layer and the parameters that determine the photovoltaic performance. Impedance spectroscopy technique, which reveals the various interfacial processes in terms of resistive and capacitive elements, is used to get an insight into the charge transport through the junction and bulk of the FTO-perovskite solar cell. Again these values were consistent with the results obtained from I-V analysis. These analyses of current– voltage (I–V) characteristics and impedance spectroscopy technique provide essential insights into the performance parameters which determine the transport mechanism and location of electron hole recombination and the efficiency of the device.