• Energy Research

Abstract In this report, large area and high-quality graphene films were synthesized under 1000 °C by chemical vapor deposition technique. Their structure, optical and electronic properties have been characterized by Raman spectroscopy, Ultraviolet–visible spectrophotometry and Hall Effect measurement system, respectively. The films were found to be perfect sp2 bonding form of graphene with a maximum size of 9 cm2. By contrasting the current–voltage feature of ITO/SiOx/Si, G/ITO/SiOx/Si and ITO/G/SiOx/Si configurations, the different roles of graphene layer to the heterojunction solar cells were discussed. The results showed that an energy conversion efficiency of 7.54% is obtained with the structure of G/ITO/SiOx/Si. The improved solar cell performance was attributed to the roles of graphene in SIS structures, such as improvement of light transmission and current flow, reduction of interfacial states and removal of Fermi pinning effect at the hetero-junctions between graphene films and oxides. The interfacial region between ITO, Graphene and Silicon was analyzed by transmission electron microscope image and X-ray photoelectron spectroscopy. It was found that the a-SiOx layer does exist between ITO film and Si substrate even without intentional oxidation treatment. The surface passivation and defect-assisted tunneling effect of the ultra-thin oxide layers was reflected by the device performance.

Abstract In this report, large area and high-quality graphene films were synthesized under 1000 °C by chemical vapor deposition technique. Their structure, optical and electronic properties have been characterized by Raman spectroscopy, Ultraviolet–visible spectrophotometry and Hall Effect measurement system, respectively. The films were found to be perfect sp2 bonding form of graphene with a maximum size of 9 cm2. By contrasting the current–voltage feature of ITO/SiOx/Si, G/ITO/SiOx/Si and ITO/G/SiOx/Si configurations, the different roles of graphene layer to the heterojunction solar cells were discussed. The results showed that an energy conversion efficiency of 7.54% is obtained with the structure of G/ITO/SiOx/Si. The improved solar cell performance was attributed to the roles of graphene in SIS structures, such as improvement of light transmission and current flow, reduction of interfacial states and removal of Fermi pinning effect at the hetero-junctions between graphene films and oxides. The interfacial region between ITO, Graphene and Silicon was analyzed by transmission electron microscope image and X-ray photoelectron spectroscopy. It was found that the a-SiOx layer does exist between ITO film and Si substrate even without intentional oxidation treatment. The surface passivation and defect-assisted tunneling effect of the ultra-thin oxide layers was reflected by the device performance.

Abstract In this paper, the photovoltaic feature of metal-boron carbide-silicon (MCS) solar cell was reported. The boron-doped diamond-like carbon thin film on n-silicon substrate has been prepared using arc-discharge plasma chemical vapor deposition (PCVD) technique. The conductivity and the resistivity of the film were measured by Bio-Rad Hall5500PC system to be p-type semiconductor and 3–12 Ω cm/□, respectively. The boron content in the films was about 0.8–1.2%, obtained from Auger electron spectroscopy (AES), and some microcrystalline diamond grains (0.5–1.0 μm) embedded in the mainly amorphous network were revealed through scanning electron microscope (SEM) and Raman spectrum. The performance of Au/C(B)/n-Si heterojunction solar cells has been given under dark I – V rectifying curve and I – V working curve (with 100 mW cm −2 illumination). A measurement of open-circuit voltage V oc =580 mV and short-circuit current density J sc =32.5 mA cm −2 was obtained. Accordingly, the energy conversion efficiency of the device was tentatively determined to be about 7.9% in AM 1.5, 100 mW/cm 2 illuminated.

Abstract In this paper, the photovoltaic feature of metal-boron carbide-silicon (MCS) solar cell was reported. The boron-doped diamond-like carbon thin film on n-silicon substrate has been prepared using arc-discharge plasma chemical vapor deposition (PCVD) technique. The conductivity and the resistivity of the film were measured by Bio-Rad Hall5500PC system to be p-type semiconductor and 3–12 Ω cm/□, respectively. The boron content in the films was about 0.8–1.2%, obtained from Auger electron spectroscopy (AES), and some microcrystalline diamond grains (0.5–1.0 μm) embedded in the mainly amorphous network were revealed through scanning electron microscope (SEM) and Raman spectrum. The performance of Au/C(B)/n-Si heterojunction solar cells has been given under dark I – V rectifying curve and I – V working curve (with 100 mW cm −2 illumination). A measurement of open-circuit voltage V oc =580 mV and short-circuit current density J sc =32.5 mA cm −2 was obtained. Accordingly, the energy conversion efficiency of the device was tentatively determined to be about 7.9% in AM 1.5, 100 mW/cm 2 illuminated.

Cooling was a very effective way to eliminate the bow of Silicon solar cell. In this paper, by a series of experiments, we found that during the cooling, the electrical characteristics and internal or external quantum efficiency nearly stayed the same, and the lifetime of minority carriers as well. The cooling was a available way to apply in industrial process.

Cooling was a very effective way to eliminate the bow of Silicon solar cell. In this paper, by a series of experiments, we found that during the cooling, the electrical characteristics and internal or external quantum efficiency nearly stayed the same, and the lifetime of minority carriers as well. The cooling was a available way to apply in industrial process.

Abstract In this paper, a series of recombination paths in Al:ZnO/ZnO/CdS/Cu(In,Ga)Se2 (CIGS) solar cell has been carried out through photoluminescence (PL) emission, optoelectronic conversion characteristic and AFORS HET simulation. Proper rapid thermal annealing (RTA) lead to the improvement of CIGS performance by reducing bulk recombination of CIGS layer and interface recombination, which opens the way to explore a useful method to significantly ameliorate the microstructure within the CIGS layer. A maximum value for the conversion efficiency was obtained when the annealing temperature was continuously increased to 400 °C, where the efficiency increased by 43%, and the recombination from the interface states, the bulk defect traps and the tunneling enhancement recombination was reduced to the lowest. The opto-electronic parameters, such as short-circuit current Jsc, open-circuit voltage Voc, reverse saturation current J0 and the series resistance Rs have been correlatively investigated to the nonradiative transition among the various defects and are strongly dependent upon the annealing temperature as well.

Abstract In this paper, a series of recombination paths in Al:ZnO/ZnO/CdS/Cu(In,Ga)Se2 (CIGS) solar cell has been carried out through photoluminescence (PL) emission, optoelectronic conversion characteristic and AFORS HET simulation. Proper rapid thermal annealing (RTA) lead to the improvement of CIGS performance by reducing bulk recombination of CIGS layer and interface recombination, which opens the way to explore a useful method to significantly ameliorate the microstructure within the CIGS layer. A maximum value for the conversion efficiency was obtained when the annealing temperature was continuously increased to 400 °C, where the efficiency increased by 43%, and the recombination from the interface states, the bulk defect traps and the tunneling enhancement recombination was reduced to the lowest. The opto-electronic parameters, such as short-circuit current Jsc, open-circuit voltage Voc, reverse saturation current J0 and the series resistance Rs have been correlatively investigated to the nonradiative transition among the various defects and are strongly dependent upon the annealing temperature as well.