Improvement of the interfacial contact between zinc oxide and a mixed cation perovskite using carbon nanotubes for ambient-air-processed perovskite solar cells

Abstract

The increasing consideration toward thin-film organic–inorganic halide perovskite solar cells (PSCs) is because of their high-power conversion efficiency that arises from several advantages of perovskite materials, including solution processability and low fabrication cost. However, we have not been able to maximize these advantages in the existing halide perovskite (PVK) solar cell technology as a consequence of structural and material limitations. Herein, we have developed a solution to these drawbacks by substituting the conventional metal–oxide photoelectrodes with materials doped with carbon nanotubes (CNTs). The mixed cation PSCs fabricated in ambient air were unstable with the PVK on top of zinc oxide (ZnO) due to the presence of hydroxyl groups on the ZnO surface. To suppress the hydroxyl groups, we incorporated CNTs in the ZnO film. On adding CNTs, the ZnO film showed more significant charge extraction, with the recombination rate in the PSC reducing due to higher conductivity and lower trap states in CNT-doped ZnO. Our results demonstrate that the optimized PSC based on the CNT additive showed PCE up to 15%. With this surface modification approach, we could show hysteresis-free and stable PSCs, with lesser decomposition after ∼2000 h of storage in a moist ambience. This work presents novelty in the material, cost, and assembly of stable and effective perovskite solar cells.