Deterministic fabrication of 3D/2D perovskite bilayer stacks for durable and efficient solar cells

Realizing solution-processed heterostructures is a long-enduring challenge in halide perovskites because of solvent incompatibilities that disrupt the underlying layer. By leveraging the solvent dielectric constant and Gutmann donor number, we could grow phase-pure two-dimensional (2D) halide perovskite stacks of the desired composition, thickness, and bandgap onto 3D perovskites without dissolving the underlying substrate. Characterization reveals a 3D-2D transition region of 20 nanometers mainly determined by the roughness of the bottom 3D layer. Thickness dependence of the 2D perovskite layer reveals the anticipated trends for n-i-p and p-i-n architectures, which is consistent with band alignment and carrier transport limits for 2D perovskites. We measured a photovoltaic efficiency of 24.5%, with exceptional stability of T-99 (time required to preserve 99% of initial photovoltaic efficiency) of >2000 hours, implying that the 3D/2D bilayer inherits the intrinsic durability of 2D perovskite without compromising efficiency.

Automated summary

Realizing solution-processed heterostructures in halide perovskites is a long-standing challenge due to solvent incompatibilities. However, by utilizing the solvent dielectric constant and Gutmann donor number, it is possible to grow phase-pure two-dimensional (2D) halide perovskite stacks with desired composition, thickness, and bandgap onto 3D perovskites without dissolving the underlying substrate. The thickness dependence of the 2D perovskite layer shows expected trends for different device architectures, indicating the influence of band alignment and carrier transport limits.