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

The combined effect of TiO2 and CeO2 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 CeO2 in combination with TiO2 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 CeO2 nanostructures. The synthesized nanoparticles were used over the TiO2 layer, and their photovoltaic performance was compared to that of the TiO2-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 CeO2 provides better light travel toward the photosensitizer, and the highest power conversion efficiency (PCE) of nearly 12.5% was recorded for the rod-shaped CeO2 in the HTL-free C-PSC, which is 24% higher compared to a pristine TiO2-based C-PSC. Moreover, the devices with rod-shaped CeO2 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.