| Work Detail |
Chinese scientists constructed a four-terminal perovskite-CIGS tandem solar cell based on a superior semitransparent perovskite device with an efficiency of 21.26% and a high bifaciality factor of 92.2%. They used a solvent annealing strategy to produce a perovskite film with full coverage, larger grains, superior crystallinity, and free of detectable lead iodide impurities. A group of researchers from Northwest Normal University (China) has fabricated a four-terminal (4T) tandem solar cell based on a semi-transparent perovskite top device and a copper-indium-gallium-selenium (CIGS) bottom cell. “To improve the crystallinity of the perovskite film used in the top perovskite cell, we employed a stepwise solvent annealing method in dimethyl sulfoxide (DMSO),” lead author Yan Li told pv magazine . “We fabricated films with a bandgap width of 1.68 eV by two consecutive heating steps: annealing at 100 °C and then at 80 °C.” The scientists explained that the first step aims to induce rapid nucleation and efficient growth of film grains with high crystallinity, while the second step aims to release DMSO molecules by preventing the sublimation of volatile organic halide species, thus avoiding the growth of the lead(II) iodide (PbI2) impurity phase. Further electrochemical impedance spectroscopy (EIS) analyses demonstrated that the stepwise solvent annealing strategy was capable of producing a perovskite film with larger grains, higher crystallinity, and a purer phase than a control sample produced using the traditional solvent annealing method. The research group constructed the superior perovskite cell with an indium tin oxide (ITO) and glass substrate, a tin oxide (SnO2) electron transport layer (ETL), the optimized perovskite absorber, a Spiro-OMeTAD hole transport layer (HTL), a molybdenum oxide (MoOx) layer, and a semi-transparent indium zinc oxide (IZO) back contact. This cell achieved a power conversion efficiency of 21.26%, an open circuit voltage of 1.210 V, a short circuit current density of 21.43 mA/cm2 and a fill factor of 0f 82.0%. It was then combined with a bottom CIGS solar cell with an efficiency of 18.29%, decreasing this efficiency value to 7.89% after the bottom device is filtered by the semi-transparent perovskite cell. “The achieved efficiency is among the highest values ??for 4-T PSC/CIGS tandem solar cells on record,” the research team stresses, noting that the result is mainly attributable to the high efficiency of the top perovskite cell and the high bifaciality factor of 92% achieved by its semi-transparent IZO electrode. The cell is described in the paper, “ A stepwise solvent-annealing strategy for high-efficiency four-terminal Perovskite/Cu(InGa)Se 2 tandem solar cells ,” published in the journal Materials Today Energy . |
