Binder-solvent effects on low temperature-processed carbon-based, hole-transport layer free perovskite solar cells

Hole transport layer and expensive metallic counter electrode free low-temperature processed, economical carbon-based perovskite solar cells are fabricated. Carbon pastes with different binders (ethyl cellulose, PVP and PMMA) and three different solvents are prepared and their perovskite compatibility is studied. The prepared carbon pastes are adherent and have low sheet resistance (8.43 Ω □−1), which is directly printed on top of FA1-xMAxPbI3-yBry based perovskite absorber layer. UV–vis absorption spectra and XRD analysis are performed to study long-term binder-induced degradation of the perovskite absorber layer. The hydrophobic carbon layer effectively blocks the moisture diffusion into the perovskite layer. The results suggest ethyl cellulose and PMMA based binders enhance the perovskite layer stability, whereas, in PVP based binder, some initial degradation is observed due to the presence of hydrophilic moiety. The perovskite solar cell with the FTO/TiO2 compact layer/TiO2 mesoporous layer/perovskite/carbon architecture is fabricated. The fabricated devices with PMMA based binder show the highest power conversion efficiency >10% and encouraging stability for more than 700 h for un-encapsulated devices in ambient conditions retaining more than 50% of its initial efficiency.