Hybrid halide perovskites are a promising class of materials for next-generation photovoltaics by combining high power conversion efficiencies, low-temperature processing[1,2] and compatibility with low-cost carbon electrode[3]. In particular, triple-mesoscopic perovskite solar cells based on TiO2/ZrO2/carbon architectures have attracted growing interest because they intrinsically improve device robustness by eliminating organic hole-transport layers and enabling monolithic and fully printable stacks.
However, interfacial stability at the carbon/perovskite interface remains a major challenge for industrial-scale integration, particularly in low-cost perovskite modules for solar or PEC/PV applications and is more made worse by intrinsic moisture sensibility of perovskite materials. Several encapsulation strategies have been proposed to mitigate this issue, including polymer barrier coatings, glass-glass sealing and inorganic barrier layers deposited by vacuum techniques[4]. Unfortunately, these approaches often increase processing complexity, cost or compromise scalability and compatibility with mesoporous carbon scaffolds. An alternative and interface-specific strategy consists in the electrochemical grafting of organic molecules onto the carbon electrode.
In this presentation, we will address the electrochemical surface modification of carbon scaffolds in triple-mesoscopic perovskite solar cells using diazonium salts. This controlled electrografting approach enables the formation of thin layers that induce hydrophobic to superhydrophobic properties to the carbon surface protecting the perovskite from moisture penetration within the mesoporous network. The grafting thickness and density can be finely tuned to preserve the intrinsic porosity and electrical conductivity of the carbon electrode[5]. A particular attention will be placed on the role of the electrochemical medium as the mesoporous device architecture imposes strict solvent constraints. The solvent must be compatible with the entire device stack and prevent dissolution or degradation of the perovskite. At the same time, it must guarantee adequate solubility of diazonium and electrolyte species while maintaining electronic accessibility of the carbon network. Together, these considerations define a low-temperature and scalable pathway for improving the interfacial stability and long-term durability of carbon-based triple-mesoscopic perovskite photovoltaic architectures.