Ieee Transactions on Electron Devices, May 1, 1984
The effect of light bias on the spectral current response and spectral capacitance characteristic... more The effect of light bias on the spectral current response and spectral capacitance characteristics of CdS/CuInSe2 thin-film heterojunction solar cells has been investigated. Monochromatic light bias has been used to identify specific wavelength regions responsible for the spectral behavior seen under white light bias. Variations with light or voltage bias are consistent with the effect of the field on interface recombination in both high and low CdS resistivity devices. Devices with high CdS resistivity show spectrally dependent enhancement and quenching effects very similar to those reported for CdS/Cu2S devices in which the space charge region was primarily in the CdS. It is concluded that in high CdS resistivity devices the junction behavior is controlled by the photoconductive CdS as has been established in CdS/Cu2S cells. Low CdS resistivity CdS/CuInSe2 devices show none of these effects.
Current-voltage (JV) analysis of poly (3-hexlythiophene)(P3HT) and phenyl-C61-butaric acid methyl... more Current-voltage (JV) analysis of poly (3-hexlythiophene)(P3HT) and phenyl-C61-butaric acid methyl ester (PCBM) organic photovoltaics (OPV) yield valuable insight into the internal physics of devices. A simple lumped circuit model, previously used to analyze various thin ...
The calculation of the space-charge density under illumination from surface photovoltage measurem... more The calculation of the space-charge density under illumination from surface photovoltage measurements has been adapted to analyze light-soaking experiments in intrinsic hydrogenated amorphous silicon (a-Si:H). We find that the positive space-charge densities increase and the space-charge widths decrease with light exposure while very little change occurs in the hole diffusion length. These results indicate that changes in electric field distribution with light soaking are important causes of degradation of amorphous silicon solar cells, rather than changes which may ocur in the hole diffusion length. We also review and discuss results of others regarding application of the surface photovoltage (SPV) to study light-induced phenomena, evidence of two different types of light-induced defects, and potential limitations of SPV in a-Si:H.
The calculation of the space-charge density under illumination from surface photovoltage measurem... more The calculation of the space-charge density under illumination from surface photovoltage measurements has been adapted to analyze light-soaking experiments in intrinsic hydrogenated amorphous silicon (a-Si:H). We find that the positive space-charge densities increase and the space-charge widths decrease with light exposure while very little change occurs in the hole diffusion length. These results indicate that changes in electric field distribution with light soaking are important causes of degradation of amorphous silicon solar cells, rather than changes which may ocur in the hole diffusion length. We also review and discuss results of others regarding application of the surface photovoltage (SPV) to study light-induced phenomena, evidence of two different types of light-induced defects, and potential limitations of SPV in a-Si:H.
Current transport in a-Si based n/p (‘‘tunnel’’) junctions is investigated using current-voltage-... more Current transport in a-Si based n/p (‘‘tunnel’’) junctions is investigated using current-voltage- temperature and quantum efficiency measurements. Currents are nearly ohmic and temperature independent under typical solar cell operating conditions. Incorporating a thin a-Si(B) p+ layer between the n and p layers and replacing either a-Si layer with a microcrystalline layer improves the device by reducing the resistance and increasing the recombination. Light soaking improves the devices slightly. These results are consistent with a recently proposed recombination-tunneling model. Incorporating improved interconnect junctions in tandem solar cell devices improved the initial and stabilized performance.
ABSTRACT We investigate the effect of sputtered transparent conducting oxide (TCO) contacts on th... more ABSTRACT We investigate the effect of sputtered transparent conducting oxide (TCO) contacts on the device performance of ss/n-i-p/TCO and glass/SnO2/p-i-n/TCO/Ag solar cells. TCO materials ITO and ZnO are compared, and found to have very similar transparency at the same sheet resistance. Sputtering ZnO with O2 in the Ar reduces FF for ss/n-i-p/ZnO devices, compared to sputtering without O2. This is attributed to an interface not bulk effect. Sputtering ITO with O2 on the same devices increases JSC due to higher ITO transparency, compared to sputtering without O2 , but has no effect on FF. Based on curvature in the J(V) curve around VOC, the ZnO/p layer contact appears to be non-ohmic. For p-i-n/TCO/Ag devices, μc-Sin-layers have much higher VOC,JSC, and FF for all variations of TCO/Ag back reflectors compared to an a-Si n-layer. Devices with ITO/Ag have lower VOC and JSC compared to devices with ZnO/Ag. Sputtering ZnO with O2 has no detrimental effect on devices with μc-Sin-layers but severely reduces FF in devices with a-Si n-layers.
3Rd World Conference Onphotovoltaic Energy Conversion 2003 Proceedings of, May 18, 2003
Copper sulfide (Cu/sub x/S) films were studied as a back contact material for CdTe solar cells. T... more Copper sulfide (Cu/sub x/S) films were studied as a back contact material for CdTe solar cells. The Cu/sub x/S films were made by chemical bath deposition in aqueous solution. Annealing at 200/spl deg/C in Ar improved the performance of the solar cells. Using the CdS/CdTe/Cu/sub x/S/C structure, an open-circuit voltage (V/sub oc/) higher than 840 mV and an energy conversion efficiency higher than 11% were obtained.
The current-voltage characteristics of a Si:H p-i-n solar cells having open-circuit voltages, V(o... more The current-voltage characteristics of a Si:H p-i-n solar cells having open-circuit voltages, V(oc), between 0.70 and 0.90 V were measured as a function of temperature and light intensity. The diode parameters (diode factor, saturation current density, and built-in voltage) were calculated in the light and in the dark. It was found that parameters obtained in the dark have no relevance to the analysis of V(oc), but they do indicate that tunneling may have a significant effect in the dark. The V(oc) is dominated by recombination at the p/i interface or in the i layer near this interface. Reducing interface recombination with a carbon buffer layer and reducing bulk recombination with less i layer impurities improves V(oc) by reducing the forward recombination current density.
Ieee Transactions on Electron Devices, May 1, 1984
The effect of light bias on the spectral current response and spectral capacitance characteristic... more The effect of light bias on the spectral current response and spectral capacitance characteristics of CdS/CuInSe2 thin-film heterojunction solar cells has been investigated. Monochromatic light bias has been used to identify specific wavelength regions responsible for the spectral behavior seen under white light bias. Variations with light or voltage bias are consistent with the effect of the field on interface recombination in both high and low CdS resistivity devices. Devices with high CdS resistivity show spectrally dependent enhancement and quenching effects very similar to those reported for CdS/Cu2S devices in which the space charge region was primarily in the CdS. It is concluded that in high CdS resistivity devices the junction behavior is controlled by the photoconductive CdS as has been established in CdS/Cu2S cells. Low CdS resistivity CdS/CuInSe2 devices show none of these effects.
Current-voltage (JV) analysis of poly (3-hexlythiophene)(P3HT) and phenyl-C61-butaric acid methyl... more Current-voltage (JV) analysis of poly (3-hexlythiophene)(P3HT) and phenyl-C61-butaric acid methyl ester (PCBM) organic photovoltaics (OPV) yield valuable insight into the internal physics of devices. A simple lumped circuit model, previously used to analyze various thin ...
The calculation of the space-charge density under illumination from surface photovoltage measurem... more The calculation of the space-charge density under illumination from surface photovoltage measurements has been adapted to analyze light-soaking experiments in intrinsic hydrogenated amorphous silicon (a-Si:H). We find that the positive space-charge densities increase and the space-charge widths decrease with light exposure while very little change occurs in the hole diffusion length. These results indicate that changes in electric field distribution with light soaking are important causes of degradation of amorphous silicon solar cells, rather than changes which may ocur in the hole diffusion length. We also review and discuss results of others regarding application of the surface photovoltage (SPV) to study light-induced phenomena, evidence of two different types of light-induced defects, and potential limitations of SPV in a-Si:H.
The calculation of the space-charge density under illumination from surface photovoltage measurem... more The calculation of the space-charge density under illumination from surface photovoltage measurements has been adapted to analyze light-soaking experiments in intrinsic hydrogenated amorphous silicon (a-Si:H). We find that the positive space-charge densities increase and the space-charge widths decrease with light exposure while very little change occurs in the hole diffusion length. These results indicate that changes in electric field distribution with light soaking are important causes of degradation of amorphous silicon solar cells, rather than changes which may ocur in the hole diffusion length. We also review and discuss results of others regarding application of the surface photovoltage (SPV) to study light-induced phenomena, evidence of two different types of light-induced defects, and potential limitations of SPV in a-Si:H.
Current transport in a-Si based n/p (‘‘tunnel’’) junctions is investigated using current-voltage-... more Current transport in a-Si based n/p (‘‘tunnel’’) junctions is investigated using current-voltage- temperature and quantum efficiency measurements. Currents are nearly ohmic and temperature independent under typical solar cell operating conditions. Incorporating a thin a-Si(B) p+ layer between the n and p layers and replacing either a-Si layer with a microcrystalline layer improves the device by reducing the resistance and increasing the recombination. Light soaking improves the devices slightly. These results are consistent with a recently proposed recombination-tunneling model. Incorporating improved interconnect junctions in tandem solar cell devices improved the initial and stabilized performance.
ABSTRACT We investigate the effect of sputtered transparent conducting oxide (TCO) contacts on th... more ABSTRACT We investigate the effect of sputtered transparent conducting oxide (TCO) contacts on the device performance of ss/n-i-p/TCO and glass/SnO2/p-i-n/TCO/Ag solar cells. TCO materials ITO and ZnO are compared, and found to have very similar transparency at the same sheet resistance. Sputtering ZnO with O2 in the Ar reduces FF for ss/n-i-p/ZnO devices, compared to sputtering without O2. This is attributed to an interface not bulk effect. Sputtering ITO with O2 on the same devices increases JSC due to higher ITO transparency, compared to sputtering without O2 , but has no effect on FF. Based on curvature in the J(V) curve around VOC, the ZnO/p layer contact appears to be non-ohmic. For p-i-n/TCO/Ag devices, μc-Sin-layers have much higher VOC,JSC, and FF for all variations of TCO/Ag back reflectors compared to an a-Si n-layer. Devices with ITO/Ag have lower VOC and JSC compared to devices with ZnO/Ag. Sputtering ZnO with O2 has no detrimental effect on devices with μc-Sin-layers but severely reduces FF in devices with a-Si n-layers.
3Rd World Conference Onphotovoltaic Energy Conversion 2003 Proceedings of, May 18, 2003
Copper sulfide (Cu/sub x/S) films were studied as a back contact material for CdTe solar cells. T... more Copper sulfide (Cu/sub x/S) films were studied as a back contact material for CdTe solar cells. The Cu/sub x/S films were made by chemical bath deposition in aqueous solution. Annealing at 200/spl deg/C in Ar improved the performance of the solar cells. Using the CdS/CdTe/Cu/sub x/S/C structure, an open-circuit voltage (V/sub oc/) higher than 840 mV and an energy conversion efficiency higher than 11% were obtained.
The current-voltage characteristics of a Si:H p-i-n solar cells having open-circuit voltages, V(o... more The current-voltage characteristics of a Si:H p-i-n solar cells having open-circuit voltages, V(oc), between 0.70 and 0.90 V were measured as a function of temperature and light intensity. The diode parameters (diode factor, saturation current density, and built-in voltage) were calculated in the light and in the dark. It was found that parameters obtained in the dark have no relevance to the analysis of V(oc), but they do indicate that tunneling may have a significant effect in the dark. The V(oc) is dominated by recombination at the p/i interface or in the i layer near this interface. Reducing interface recombination with a carbon buffer layer and reducing bulk recombination with less i layer impurities improves V(oc) by reducing the forward recombination current density.
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