# Investigation of the Effect of Molecules Containing Sulfonamide Moiety Adsorbed on the FAPbI3 Perovskite Surface: A First-Principles Study

## TL;DR

This study uses computer simulations to show how sulfonamide molecules can stabilize and improve the performance of perovskite solar cell surfaces.

## Contribution

The paper introduces a first-principles analysis of sulfonamide molecules' effects on FAPbI3 perovskite surfaces, highlighting structural and electronic impacts.

## Key findings

- C2H12N6O4S shows the strongest adsorption and binding stability due to its extended framework and electron groups.
- Adsorption significantly alters the electronic structure and enhances charge coupling on the PbI2-terminated surface.
- Optical properties improve with a red-shift in absorption and increased intensity for all adsorption systems.

## Abstract

First-principles calculations were conducted to examine the impact of three sulfonamide-containing molecules (H4N2O2S, CH8N4O3S, and C2H2N6O4S) adsorbed on the FAPbI3(001) perovskite surface, aiming to establish a significant positive correlation between the molecular structures and their regulatory effects on the perovskite surface. A systematic comparison was conducted to evaluate the adsorption stability of the three molecules on the two distinct surface terminations. The results show that all three molecules exhibit strong adsorption on the FAPbI3(001) surface, with C2H12N6O4S demonstrating the most favorable binding stability due to its extended frameworks and multiple electron-donating/withdrawing groups. Simpler molecules lacking carbon skeletons exhibit weaker adsorption and less dependence on surface termination. Ab initio molecular dynamics simulations (AIMD) further corroborated the thermal stability of the stable adsorption configurations at elevated temperatures. Electronic structure analysis reveals that molecular adsorption significantly reconstructs the density of states (DOS) on the PbI2-terminated surface, inducing shifts in band-edge states and enhancing energy-level coupling between molecular orbitals and surface states. In contrast, the FAI-terminated surface shows weaker interactions. Charge density difference (CDD) analysis indicates that the molecules form multiple coordination bonds (e.g., Pb–O, Pb–S, and Pb–N) with uncoordinated Pb atoms, facilitated by –SO2–NH2 groups. Bader charge and work function analyses indicate that the PbI2-terminated surface exhibits more pronounced electronic coupling and interfacial charge transfer. The C2H12N6O4S adsorption system demonstrates the most substantial reduction in work function. Optical property calculations show a distinct red-shift in the absorption edge along both the XX and YY directions for all adsorption systems, accompanied by enhanced absorption intensity and broadened spectral range. These findings suggest that sulfonamide-containing molecules, particularly C2H12N6O4S with extended carbon skeletons, can effectively stabilize the perovskite interface, optimize charge transport pathways, and enhance light-harvesting performance.