Improving Efficiency and Stability of Carbon‐Based Perovskite Solar Cells by a Multifunctional Triple‐Layer System: Antireflective, UV‐Protective, Superhydrophobic, and Self‐Cleaning

Low‐cost carbon‐based perovskite solar cells (C‐PSCs) without a hole transport layer (HTL) and metal contact are highly promising for marketing. However, lower efficiency than conventional PSCs and instability during the penetration of moisture through the porous carbon electrode as well as the incoming of ultraviolet (UV) light from the glass side of the device remain challenges. Herein, a multifunctional triple‐layer system containing TiO 2 /SiO 2 /CeO 2 porous nanomaterials is numerically simulated and experimentally used on the glass side of HTL‐free C‐PSCs. This strategy is designed to increase cell efficiency by enhancing the antireflective feature and long‐term stability via the UV light blocking and superhydrophobic properties introduced to the surface. Furthermore, this system is durable against environmental pollutants due to the photocatalytic self‐cleaning effect of TiO 2 . A superhydrophobic carbon back contact is also used to sandwich the perovskite active layer between two superhydrophobic surfaces and further the humidity resilience of the device. The device with polydimethylsiloxane (PDMS)–TiO 2 /SiO 2 /CeO 2 /glass/meso‐TiO 2 /MAPbI 3 /superhydrophobic‐carbon configuration shows an efficiency of 16.60% among the HTL‐free C‐PSCs and superior long‐term stability (maintaining 98.5% of the initial efficiency without encapsulation) against UV light and relative humidity of 90% at 50 °C.