Dual Interface Modification for Reduced Nonradiative Recombination in n-i-p Methylammonium-Free Perovskite Solar Cells.

High defect concentrations at the interfaces are the basis of charge extraction losses and instability in perovskite solar cells. Surface engineering with organic cations is a common practice to solve this issue. However, the full implications of the counteranions of these cations for device functioning are often neglected.

Self-similar optical transmittance for a deterministic aperiodic multilayer structure.

We study theoretically the spectral transmission properties of a multilayer structure in which the refractive index of the layers follows a self-similar arithmetical sequence named 'The 1s-counting sequence', which is related to the Pascal's triangle. The transmittance spectrum is intermediate between that of a periodic structure and that of a random structure, and shows clearly properties of scaling and self-similarity for all incident angles and TE and TM polarizations.