Light stability tests of CH₃NH₃PbI₃ perovskite solar cells using porous carbon counter electrodes

The CH₃NH₃PbI₃ perovskite solar cells have been fabricated using three-porous-layered electrodes as, 〈glass/F-doped tin oxide (FTO)/dense TiO₂/porous TiO₂-perovskite/porous ZrO₂-perovskite/porous carbon-perovskite〉 for light stability tests. Without encapsulation in air, the CH₃NH₃PbI₃ perovskite solar cells maintained 80% of photoenergy conversion efficiency from the initial value up to 100 h under light irradiation (AM 1.5, 100 mW cm^-2). Considering the color variation of the CH₃NH₃PbI₃ perovskite layer, the significant improvement of light stability is due to the moisture-blocking effect of the porous carbon back electrodes. The strong interaction between carbon and CH₃NH₃PbI₃ perovskite was proposed by the measurements of X-ray photoelectron spectroscopy and X-ray diffraction of the porous carbon-perovskite layers.