Porous Anatase TiO₂ Nanocrystal Derived from the Metal–Organic Framework as Electron Transport Material for Carbon-Based Perovskite Solar Cells

Abstract

Fully printable, hole-conductor-free, carbon-based perovskite solar cells are attractive and promising for industrial production due to their low cost and high stability. However, the efficiency of this type of device is difficult to improve due to the undesirable interfacial contact during the printing process compared to the spin coating process and the higher recombination ratio than the devices with a hole conductor. Herein, a porous anatase nanocrystal (Nano-TiO2) derived by MIL-125, a type of titanium-based metal–organic frameworks (MOFs), was used as the electron transporting material (ETM). The Nano-TiO2 can be conveniently covered on a substrate by screen-printing and still maintain the cakelike morphology, which is beneficial to large-scale production. Moreover, the cakelike morphology composed of nanocrystals is more favorable for the crystallization of perovskites than commercial TiO2 (P25) and can reduce the recombination of photogenerated electron–hole pairs to improve device performance. The device based on Nano-TiO2 shows a VOC of 0.907 V and a fill factor of 68.14% at the forward scan, which is higher than that of the devices based on P25 (0.853 V and 52.95%). It paves a promising way for carbon-based printable perovskite solar cells.