Improved Interfacial Contact Between “Perovskite/Electron‐Transport Layer” by Hydrophilic Molecule to Achieve Efficiency >14%, Carbon Electrode‐Based, Hole‐Conductor‐Free, Low‐Temperature Mesoscopic Perovskite Solar Cells

Abstract

Interfacial contact between “perovskite/electron‐transport layer” (PVSK/ETL) has appeared as a bottleneck for the hole‐conductor‐free, mesoscopic perovskite solar cells (meso‐CPSCs) based on carbon electrode, especially for the low‐temperature devices. To solve this problem, hydroxypropyl‐β‐cyclodextrin is imported to TiO2‐based ETL. It is observed that this treatment improves the wettability of ETL, enhances the crystallization processes of PVSK in the mesoporous skeleton, and strengthens the interfacial contact between “PVSK/ETL”. Besides, defects are reduced at the interface. Accordingly, charge extraction is accelerated, while recombination is retarded. Transient photovoltage/photocurrent decay curve test shows that the charge‐extraction time decreases from 3.75 (±0.38) to 3.42 (±0.22) μs, while lifetime of photogenerated charges in device is prolonged from 10.00 (±2.38) to 12.23 (±1.86) μs, which helps to upgrade power μconversion efficiency from 9.38 (±1.28)% to 11.42 (±0.80)% (optimized at 12.44%). The efficiency is further upgraded to 14.04% after modifying the carbon electrode with octylammonium iodide. Such efficiency catches up with 85% of that of high‐temperature meso‐CPSCs (prepared at 450 °C) when using (5‐AVA)x(MA)1−xPbI3 as light absorber. The study paves the way to further upgrade the efficiency of the low‐temperature meso‐CPSCs.