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32nd European Photovoltaic Solar Energy Conference and Exhibition; 1372-1374, In this study, three front-side electrodes consisting of AuGe/Au metal-finger with anti-reflective layer (ARL), ITO-finger with ARL, and ITO-overcoated types without ARL were fabricated for InGaP/GaAs dual-junction solar cells, and samples A, B, and C were used to denote these three devices, respectively. For the sample C with ITO-overcoated electrode, the 200-nm-thick ITO film with a high transmittance of 91% in the visible wavelength range was deposited. The results obtained from the current density-voltage measurements indicated the short-circuit current densities (Jsc) of samples A, B, and C are 9.61, 11.16, and 11.65 mA/cm2, respectively. Meanwhile, the conversion efficiencies of these three solar cells are measured to be 17.50%, 20.41%, and 20.92%, respectively. After replacing the AuGe/Au metal-finger electrode with the ITO-overcoated electrode, there is 19.5% improvement in the conversion efficiency occurred in the device. Moreover, because the ITO front-side electrode can cover overall surface of the device, all regions on the surface of sample C would extract the electrons, resulting in the highest Jsc. Not only, the ITO was also used to be ARL and enhanced the device performance.

31st European Photovoltaic Solar Energy Conference and Exhibition; 1411-1413, In this study, high-quality In0.16Ga0.84As epitaxial films can be achieved by employing the linear graded buffer layer. The front electrodes with stripe shape were prepared for the cell devices. Additionally, to fabricate the In0.16Ga0.84As solar cell with high efficiency, we prepared the front electrode patterns with various angles from 0° to 90° that defined as the included angles between the electrode and [110] direction of the GaAs wafer. As this included angle was fixed at 45°, the lower conversion efficiency of In0.16Ga0.84As solar cell was measured to be 14.61%. However, when the included angles were varied to 0° and 90°, the higher conversion efficiencies of In0.16Ga0.84As solar cells can be enhanced to 16.34% and 16.58%, respectively. Obviously, with designing the included angles of 0° and 90°, the hole carriers in the devices can be avoided to meet the dislocations in the epilayers efficiently, resulting in the improvement of the conversion efficiency.

26th European Photovoltaic Solar Energy Conference and Exhibition; 800-802, Crack-free thin film solar cell is released from GaAs substrate by cross-shaped pattern epitaxial lift-off (CPELO) technology. The cross-shaped pattern array is used to define cell size and provide the etch path of etchant solution. The AlAs sacrificial layer is etched by hydrofluoric acid etchant through the cross-shaped holes. Results indicate that the entire wafer can be etched simultaneously. The CPELO technique does not require a temporary carrier substrate to transfer the epilayers because the permanent carrier substrate is directly deposited onto the epilayers before the epitaxial lift-off process. The permanent carrier, the electroplated nickel substrate, can directly contact to the epilayer without wax or low-viscosity epoxy, and can also be applied to a controllable external force via magnetic attraction to reduce the release time. The release time of the 2-inch wafer with different cell sizes (1 to 25 mm2) is about 2 to 6 hours. After CPELO process, the separated GaAs substrate can be recycled via chemical cleaning. The performance of the obtained thin film solar cell is 0.95 V, 14 mA/cm2, 84 %, 11.17 % for Voc, Jsc, FF and , respectively.

26th European Photovoltaic Solar Energy Conference and Exhibition; 62-64, Double heterojunction p-InGaN/i-InGaN/n-GaN solar cells have been fabricated and characterized in this study. Two kinds of sapphire substrate, including conventional sapphire substrate (CSS) and pattern sapphire substrates (PSS), were used for epitaxial growth in this experiment setup. High open-circuit (VOC) of 2.05 V and 2.08 V of double heterojunction InGaN-based solar cell grown on CSS and PSS substrate were demonstrated, respectively. Being difference with solar cell grown on CSS substrate, solar cell grwon on PSS substrate shows an improvement of 27.6% in short-circuit current. Such an improvement can be contributed to the low edge-dislocation density of epitaxial films and the increase of light absorption path due to scattering at patterned surface for solar cell grown on PSS substrate.