Stable monolithic hole-conductor-free perovskite solar cells using TiO2 nanoparticle binding carbon films

Abstract

Using TiO2 nanoparticles as binders, highly conductive carbon films were prepared and used to fabricate monolithic hole-conductor-free perovskite solar cell in air. Carbon films were condensed by dehydration reaction between surface hydroxyls from both TiO2 nanoparticles and carbon particles, which is beneficial for adhesion ability and conductivity of carbon film, and the formation and filling properties of perovskite crystallites in the monolithic structure of “FTO/CTiO2/M-TiO2/M-ZrO2/Carbon” (C-Compact, M-Mesoporous). A reduced sheet resistance from 10 to 2.74 Ω/sq was obtained for carbon films annealed under relatively low temperature annealing. Confined distribution of perovskite crystallites in the region containing M-TiO2/M-ZrO2 layers and bottom of carbon film was obtained from 350 °C annealing, which helped to achieve upgraded power conversion efficiency (reverse scan) from 5.40 (±1.32) % to 9.21(±1.04) % (averaged) and 11.07% (champion) at testing area of ∼0.18 cm2, as well as stability of 1000 h in relative high humidity environment (RH:70–90%). The air-compatible fabrication process, sound device ability as well as low-cost of carbon materials make such monolithic device structure realistic candidate for mass production of perovskite solar cells.