Influence of Adjustable CeO2 Morphology on the Performance of Ambient Hole Transport Layer-Free Carbon-Based Perovskite Solar Cells.

The combined effect of TiO 2 and CeO 2 as the electron transport layer (ETL) in the hole transport layer (HTL)-free carbon-based perovskite solar cells (C-PSCs) to enhance performance characteristics is a less explored research area. In this context, we investigated the effect of morphology-tuned CeO 2 in combination with TiO 2 in the C-PSCs. Considering the light scattering effect in C-PSCs and the property of extending the light-traveling distance across the photoelectrode, we synthesized rod and cubic CeO 2 nanostructures. The synthesized nanoparticles were used over the TiO 2 layer, and their photovoltaic performance was compared to that of the TiO 2-only C-PSC and analyzed by using impedance and quantum efficiency studies. The light-scattering effect on the C-PSCs, investigated with the diffused reflectance study, found that the rod structure of CeO 2 provides better light travel toward the photosensitizer, and the highest power conversion efficiency (PCE) of nearly 12.5% was recorded for the rod-shaped CeO 2 in the HTL-free C-PSC, which is 24% higher compared to a pristine TiO 2-based C-PSC. Moreover, the devices with rod-shaped CeO 2 demonstrated suitable charge transport properties along the perovskite layer and a lower charge recombination rate when compared with the cube structure. This work demonstrates a major breakthrough in the performance enhancement of HTL-free C-PSCs by nanomaterial morphology alteration and fabrication engineering, which can significantly influence future research.