Multifunctional 4-azidobenzoic acid interface engineering enables high-efficiency carbon-based perovskite solar cells

Carbon-based perovskite solar cells (C-PSCs) have received significant attention due to their low cost, simple fabrication process, and enhanced stability, with the power conversion efficiency (PCE) reaching up to 22 %. However, the interface between perovskite and hole transport materials (HTMs) like P3HT remains a critical challenge, often leading to poor contact and reduced device performance. To address this issue, various strategies have been explored to enhance interfacial contact and optimize charge extraction. In this work, we introduce 4-azidobenzoic acid (4-ABA) as an effective interface modification additive. The azide groups in 4-ABA provide crosslinking sites with P3HT, while the -COOH group passivates defects by coordinating with uncoordinated Pb²⁺ ions in the perovskite layer. This modification significantly enhances the interface contact condition, suppressing non-radiative recombination and improving device performance. As a result, the PCE of the device increases from 16.76 % to 19.16 %, and the treated device maintains 89 % of the initial PCE after 720 h of exposure to air without surface encapsulation.