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Malaysian researchers have simulated a mixed-cation perovskite solar cell that integrates tin and germanium into the absorber. By modulating the thickness of the perovskite layer, they achieved an efficiency ranging between 24.25% and 31.49%.
A group of researchers led by Universiti Malaysia Perlis in Malaysia has designed a mixed-cation perovskite solar cell based on a perovskite absorber that integrates tin (Sn) and germanium (Ge) as mixed B cations.
Perovskite absorbers using mixed cations, commonly referred to as cation A and cation B, exhibit greater stability, light absorption, and greater charge carrier mobility. The A cations are used to control the bandgap and stability of the perovskite material, while the B cations are intended to modify the electrical and optical characteristics of the perovskites.
The scientists explained that the use of both elements in the B cation through “compositional engineering” makes it possible to reduce their respective defects and increase the performance of the cell, compared to the use of each of them separately. Furthermore, Ge atoms can replace Sn atoms in the perovskite crystal structure.
“This substitution helps avoid the formation of vacancies that can occur when Sn atoms are missing,” they added. “The addition of Ge fills these vacancies, stabilizing the crystal structure and reducing defects. “Ge can also act as a substitute ion, specifically Ge2+, which helps maintain the charge balance in the crystal lattice and reduces the appearance of charged defects.”
The scientists used the SCAPS-1D solar cell capacitance software, developed by Ghent University, to simulate the novel cell configuration. The cell was based on a glass substrate and fluorine-doped tin oxide (FTO), an electron transport layer (ETL) based on tin oxide (SnO2) or titanium dioxide (TiO2), the perovskite absorber that integrates Sn and Ge, a hole transport layer (HTL) made with Spiro-OMeTAD or copper(II) oxide (Cu2O), and a gold (Au) metal contact.
The team simulated the cell with different parameters, such as layer thickness, bandgap, electron affinity, and relative dielectric permittivity, among others. He assumed that the thickness of the absorber ranged from 300 nm to 6,000 nm.
Simulated under standard lighting conditions, a solar cell with a 300 nm thick absorber achieved a power conversion efficiency of 25.23%, an open circuit voltage of 1.0410 V, a short circuit current density of 27 .4995 mA/cm2 and a fill factor of 88.14%. In contrast, a device with a 6,000 nm thick absorber achieved an efficiency of 31.73%, an open circuit voltage of 1.0426 V, a short circuit current density of 34.5235 mA/cm2 and a factor of 88.11% filling.
“The increase in the light collected at the maximum wavelength (920 nm) from 20.36% to 58.89% as the thickness of the perovskite layer increases from 300 nm to 1,200 nm indicates better capture of the light and a reduction in reflection losses,” the academics explain. “Furthermore, the fill factor between 87% and 88%, with an increase in efficiency from the initial configuration of 24.25% to an optimal condition of 31.49% at 293 K, shows that these solar cells have managed to pick up and transport cargo carriers.”
The novel architecture of the cells was presented in the study “ Mixed cations tin-germanium perovskite: A promising approach for enhanced solar cell applications, ” published in Helyion . Looking ahead, the researchers say they want to validate the accuracy of the models, identify discrepancies and refine research parameters. |
