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

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 TiO 2 -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− x PbI 3 as light absorber. The study paves the way to further upgrade the efficiency of the low-temperature meso-CPSCs.