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The novel solar cell uses antimony trisulfide (Sb2S3) as the back surface field (BSF) layer. According to its creators, this layer can be included in conventional CIGS solar cells to improve their efficiency and reduce the cost of the absorbing material.
An international group of scientists has proposed a new copper indium gallium selenide (CIGS) solar cell structure that uses antimony trisulfide (Sb2S3) as a back surface field (BSF) layer.
Sb2S3 is a promising candidate for the photovoltaic community due to its Earth-abundant and environmentally friendly constituent elements, along with suitable optoelectronic properties, such as a desirable band gap of around 1.7 eV, a great absorption coefficient and long-term stability.
BSF layers consist of a higher doping region on the back surface of the solar cell and are commonly used to increase the voltage of a device. “Sb and S are available in abundance on Earth. Hence, the incorporation of a thick layer of Sb2S3 in industrial CIGS solar cells can effectively reduce their production costs,” the researchers say. “By reducing the thickness and cost of the CIGS absorbent layer, this approach promises to make solar energy more accessible and sustainable.”
They numerically simulated and optimized the solar cell using the SCAPS-1D solar cell capacitance software, developed by Ghent University, to simulate the novel cell design.
The academics fabricated the cell with a back contact layer made of nickel (Ni), the Sb2S3-based BSF layer, a CIGS absorber, an electron transport layer (ETL) made of tin disulfide (SnS2), a window layer based on fluorine-doped tin oxide (FTO) and a front electrode made of aluminum (Al).
In the simulation, the researchers optimized the thicknesses of the buffer, absorbent and BSF layers. They also investigated acceptor density, defect density, capacitance-voltage (CV), interface defect density, generation and recombination rates, operating temperature, current density, and quantum efficiency.
“After details optimization, the optimal thicknesses for the FTO window, CIGS absorber, SnS2 buffer, and Sb2S3 BSF layers are found to be 0.05 µm, 1.0 µm, 0.05 µm, and 0.20 µm , respectively,” the group said. “The large thickness of the buffer creates series resistance and absorption losses in the solar cell structure. Since the buffer allows light to enter the solar cell device, excellent transparency and appropriate thickness are needed, which is 0.05 mm for the SnS2 buffer in our proposed structure.”
With those optimized parameters, the simulated double heterojunction (DH) cell had a power conversion efficiency of 31.15%, an open circuit voltage of 1.08 V, a short circuit current density of 33.75 mA cm2 and a fill factor of 88.50%. An optimized and simulated reference CIGS cell without the Sb2S3 BSF layers achieved an efficiency of 22.14%, an open circuit voltage of 0.91 V, a short circuit current density of 28.21 mA cm2 and a 86.31% filling.
“The results of this study provide information on the development of an ultrathin layer of Sb2S3 BSF, which can be included in conventional CIGS solar cells to improve their efficiency and reduce the cost of the absorbent material,” the group concludes.
Their findings and the solar cell concept were presented in the study “ Improving the efficiency of a CIGS solar cell to above 31% with Sb2S3 as a new BSF: a numerical simulation approach by SCAPS-1D ” solar CIGS above 31% with Sb2S3 as new BSF: a numerical simulation approach using SCAPS-1D), published in RSC Advances . The team consisted of scientists from Bangladeshs Begum Rokeya University, Hajee Mohammad Danesh University of Science and Technology and Pabna University of Science and Technology, as well as Mexicos Autonomous University of Querétaro, Al-Science University. Karkh of Iraq and King Khalid University of Saudi Arabia. |
