# Suppressing NiOx/CsPbIBr2 Interfacial Redox Reactions and Band Energy Misalignment in Perovskite Solar Cells

## TL;DR

Researchers improved the efficiency and stability of perovskite solar cells by modifying the interface with N-dodecylphosphonic acid.

## Contribution

A new interfacial modification strategy using N-dodecylphosphonic acid to suppress redox reactions and improve performance in perovskite solar cells.

## Key findings

- The NDPA interlayer suppresses redox reactions and reduces energy level mismatch at the NiOx/CsPbIBr2 interface.
- Optimized solar cells achieved a power conversion efficiency of 9.28% and an open-circuit voltage of 1.12 V.
- Modified devices retained 79% of their initial efficiency after 1300 hours of storage.

## Abstract

Inverted inorganic CsPbIBr2 perovskite solar cells (PSCs) employing NiOx as the hole‐transport layer are promising long‐term stable and semi‐transparent photovoltaic devices. Nevertheless, their performance is often constrained by unfavorable interfacial phenomena, including detrimental redox reactions between Ni3+ in NiOx and I− in perovskite, as well as band energy misalignment at the NiOx/CsPbIBr2 interface. In this work, we introduce an N‐dodecylphosphonic acid (NDPA) interfacial modification strategy, where the phosphonic groups of NDPA anchor onto the NiOx surface. This tailored interface not only suppresses interfacial redox reactions but also alleviates energy level mismatch and releases the residual tensile stress, thereby facilitating charge transport and reducing non‐radiative recombination losses. As a result, the optimized PSCs deliver a champion power conversion efficiency of 9.28% with a high open‐circuit voltage (V
oc) of 1.12 V, positioning it among the best‐performing inverted CsPbIBr2 PSCs reported to date. The modified devices retain 79% of their initial efficiency after 1300 h of storage in a nitrogen‐filled glovebox, underscoring their potential for practical photovoltaic applications.

High‐performance inverted inorganic CsPbIBr2 perovskite solar cells are achieved by introducing a N‐dodecylphosphonic acid interlayer at the NiOx/CsPbIBr2 interface.