Researchers led by the Masinde Muliro University of Science and Technology in Kenya have designed a solar cell with an absorber based on copper antimony sulfide (CuSbS2), which is a non-toxic and earth-abundant semiconductor material with promising prospects in photovoltaics, due to its high absorption coefficient and suitable bandgap.
The scientists numerically simulated and optimized the solar cell via the SCAPS–1D solar cell capacitance software, which is a simulation tool for thin-film solar cells developed by the University of Ghent in Belgium.
The solar cell was designed with a transparent substrate made of glass and fluorine-doped tin oxide (FTO), a hole transport layer (HTL) based on cadmium sulfide (CdS), the CuSbS2 absorber, an electron transport layer (ETL) made with carbon (C), and a gold (Au) metal contact.
FTO and CuSbS2 have an energy bandgap of 3.5 eV and 1.5 eV, respectively, while for CdS and C these values are 2.42 eV and 3 V, respectively.
“Cadmium sulphide was used as an electron transport layer hence preventing holes from reaching the front contact,” the researchers said. “FTO was preferred to ITO because it has special characteristics in chemical inertness, upon heating it is stable, hard mechanically, a good conductor, relatively cheap and its sheet resistance remains constant during sintering.”
To optimize the device, the academics investigated different thicknesses of FTO, CdS, C, CuSbS2, as well as the defect and dopant concentration in the absorber. They found that FTO should have a thickness of 100 nm. Furthermore, they found that CdS, CuSbS2, and C should have a thickness of 50 nm, 300 nm, and 100 nm, respectively.
The optimized cell achieved a power conversion efficiency of 16.17%, an open-circuit voltage of 0.9389 V, a short-circuit current density of 28.32 mA/cm2, and a fill factor of 60.8%.
“The variation of dopant concentration revealed that an increase in dopant concentration led to an increment in efficiency of the photovoltaic cell,” they explained. “Defect density increase led to a decrease in diffusion length indicating augmented recombination rate.”
The new cell concept was introduced in the paper “Numerical study of copper antimony sulphide (CuSbS2) solar cell by SCAPS-1D,” published in Heliyon.
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