Researchers from Helmholtz-Zentrum Berlin (HZB) have demonstrated the scalable fabrication of perovskite/silicon tandem solar cells with optimized bandgap using the slot-die coating method. The team used slot-die coating for an efficient, 1.68 eV wide bandgap triple-halide (3halide) perovskite absorber, (Cs0.22FA0.78)Pb(I0.85Br0.15)3 + 5 mol % MAPbCl3. The team demonstrated that the fabrication route is suitable for tandem solar cells without phase segregation.
The researchers successfully fabricated a triple-halide perovskite film with top cell optimized bandgaps, high PL quantum yield (PLQY), and improved film quality using the slot-die coating method. They have also efficiently integrated halide perovskites with industrial silicon bottom cells in a tandem architecture, demonstrating the potential of fabricating industrially relevant and scalable perovskite solar cells.
The chloride in triple-halide perovskites reduced the amount of bromide required for top cell optimized bandgaps, improved surface morphology, and induced surface passivation. The addition of five mol % MAPbCl3 into the double-cation Cs22Br15 perovskites increased their bandgap from 1.63 eV to 1.68 eV, which resulted in exceptional optoelectronic properties and no phase segregation.
The optimization of the annealing and drying conditions from 100 to 170 oC for 20 min improved the transient and absolute PL in charge carrier lifetimes and QFLS. Optimized crystallization and annealing conditions enabled large gain sizes, which reduced the charge collection losses, leading to higher current density in the perovskite/silicon tandem solar cells.
An optimized trade-off was identified between the detrimental large lead iodide (PbI2) aggregate formation on the film’s top surface and sample crystallinity when the film was annealed at 150 oC. A stabilized power output of 19.4% was achieved due to improved cell performance and stability of halide perovskites single-junction cells. The power output was highest for halide perovskites with top cell optimized bandgaps.
A two-terminal monolithic perovskite/tandem solar cell with 25.2% PCE on one cm2 active area was fabricated by integrating the optimized perovskite absorber layers with silicon bottom cells.
