Honeycomb-Type TiO2 Films Toward a High Tolerance to Optical Paths for Perovskite Solar Cells

Given the advantages of high power conversion efficiencies (PCEs), antisolvent-step free production, and suitability for device production in ambient conditions, perovskite solar cells (PSCs) based on ionic-liquid solvents have attained particular research interest. To further improve device performance, light management could be optimized to increase light harvesting in the perovskite layer. Here, ordered honeycomb-like TiO2 (Hc-TiO2) structures with a periodicity of around 450 nm were fabricated through a sacrificial template method. With this photonic crystal structure, the control to light flow and the confinement effect for perovskite growth were achieved simultaneously in the Hc-TiO2, leading to improved light absorption as well as preferred crystal orientation. Furthermore, a reduced trap-state density and a well-aligned energy level induced by the perovskite/pore interlayer facilitated the charge-carrier extraction from the perovskite layer to electron transport layer. As a result, the structured devices performed better than the planar cells. And the angular dependent J-V sweeps show that the structured device reserved 76 % of its initial short circuit current density (J(sc)), whereas the planar cell showed more than a half loss under the incident light of 40 degrees, demonstrating a reduced downward trend in J(sc) with the presence of photonic crystal structures. This occurrence also suggests that the structured PSCs in this work have a high tolerance to optical path changes.

Automated summary

By fabricating ordered honeycomb-like TiO2 structures, this study achieved control over light flow and confinement effect for perovskite growth, leading to improved light absorption and high tolerance to optical path changes in structured perovskite solar cells.