Unveiling the Role of Lewis Base Strength in Small-Molecule Passivation of Defect Perovskites

TL;DR

This study investigates how the strength of Lewis bases influences the passivation of defect sites in perovskite materials, revealing that phosphonic acid groups effectively improve electronic properties and stability.

Contribution

It introduces a targeted small-molecule passivation strategy using Lewis bases, highlighting the effectiveness of phosphonic acid derivatives in defect mitigation.

Findings

Phosphonic acid groups effectively passivate Pb(II) defect sites.

Passivation lowers Fermi level and increases work function.

Electronic properties are significantly restored through targeted passivation.

Abstract

Perovskite materials are highly promising for a range of optoelectronic applications including energy conversion technologies, owing to their high charge-carrier mobilities, adaptability of bandgap tuning, and exceptional light-harvesting capabilities. Yet, defects that arise during manufacturing often lead to performance limitations such as hindered efficiency and stability. This is primarily due to significant deviations in crystal geometry and band structure elements such as the Fermi level, work function, and density of states, compared to pristine perovskite. To mitigate these issues, this study explored the passivation of surface iodide-vacancy defect in perovskite using small-molecule Lewis bases, an approach aims to counteract these detrimental effects. Among the examined N-, P- and O-coordinated benzyl derivatives, those featuring a phosphonic acid group as a passivator for the undercoordinated Pb(II) sites demonstrated outstanding electronic structure properties. This was notably achieved by lowering the Fermi level, increasing the work function, and suppressing surface trap states. The effective restoration of electronic properties achieved by targeted small molecule passivation provides crucial insights into enhanced functionality and efficiency for defect perovskite materials.