Chinese researchers have used metal-organic chemical vapor deposition (MOCVD) to produce a 12 cm2, five-junction solar cell with a minimal amount of mismatch. The breakdown voltage of the cell is 4.727 V, the short-circuit current density is 860 mA/m2 and the fill factor is 86.38%.
Junhua Long, corresponding author of the study, expressed optimism about the commercial viability of the cell configuration. “We have not yet estimated the cost of the cell, but its configuration may be suitable for commercial production,” he said pv magazine.
Using metal-organic chemical vapor deposition (MOCVD), the researchers fabricated a 12 cm2 device with an AlGaInP-AlGaAs-GaAs-InGaAs-InGaAs structure. Each subcell has a specific bandgap energy with values of 2.0 eV, 1.67 eV, 1.42 eV, 1.18 eV, and 0.83 eV.
The researchers highlighted the 13.5 nm square root roughness of the cell surface, which explains its importance in reducing dislocation slip barriers and minimizing defect density in the active region.
“So the lower the surface roughness of the epilayer, the better the quality of the mismatch growth,” they said.
To solve stress-related problems, Chinese researchers used low-temperature bonding techniques that effectively reduce stress-induced defects in epitaxial materials. Additionally, they deposited an antireflective coating (ARC) composed of titanium oxide and aluminum oxide (TiOx/Al2O3) using electron beam evaporation.
The 5J solar cell evaluated under normal lighting conditions achieved significant performance metrics. It recorded a power conversion efficiency of 35.1%, an open circuit voltage of 4.727V, a short circuit current density of 860mA/m2 and a duty cycle of 86.38%.
The researchers attributed the exceptional performance of the large 5J solar cell to the low mismatch of the material and the simplicity of the manufacturing process of the flexible device.
They presented the solar cell in the paper “Fabrication of Flexible and Large-Scale Inverse Metamorphic Five-Junction Solar Cells,” published recently Advances in solar power. The group includes researchers, e.g University of Science and Technology of China and Chinese company Tianjin San’an Optoelectronics.
“Successful fabrication of large size flexible 5J IMM sun- cells No only promote the still improvement / the photoelectric conversion efficiency of multiple junction solar cells, but may also further expand the potential application,” they concluded.