Design and simulation investigations on charge transport layers-free in lead-free three absorber layer all-perovskite solar cells.

The multiple absorber layer perovskite solar cells (PSCs) with charge transport layers-free (CTLs-free) have drawn widespread research interest due to their simplified architecture and promising photoelectric characteristics. Under the circumstances, the novel design of CTLs-free inversion PSCs with stable and nontoxic three absorber layers (triple Cs₃Bi₂I₉, single MASnI₃, double Cs₂TiBr₆) as optical-harvester has been numerically simulated by utilizing wxAMPS simulation software and achieved high power conversion efficiency (PCE) of 14.8834%. This is owing to the innovative architecture of PSCs favors efficient transport and extraction of more holes and the slender band gap MASnI₃ extends the absorption spectrum to the near-infrared periphery compared with the two absorber layers architecture of PSCs. Moreover, the performance of the device with p-type-Cs₃Bi₂I₉/p-type-MASnI₃/n-type-Cs₂TiBr₆ architecture is superior to the one with the p-type-Cs₃Bi₂I₉/n-type-MASnI₃/n-type-Cs₂TiBr₆ architecture due to less carrier recombination and higher carrier life time inside the absorber layers. The simulation results reveal that Cs₂TiF₆ double perovskite material stands out as the best alternative. Additionally, an excellent PCE of 21.4530% can be obtained with the thicker MASnI₃ absorber layer thickness (0.4 µm). Lastly, the highest-performance photovoltaic devices (28.6193%) can be created with the optimized perovskite doping density of around E15 cm³ (Cs₃Bi₂I₉), E18 cm³ (MASnI₃), and 1.5E19 cm³ (Cs₂TiBr₆). This work manifests that the proposed CTLs-free PSCs with multi-absorber layers shall be a relevant reference for forward applications in electro-optical and optoelectronic devices.