Active SnO_2 Crystal Planes Enable Efficient and Ultra-Bendable n-i-p Perovskite Solar Cells with Record Certificated Power Conversion Efficiency

摘要

The tin (Ⅳ) oxide (SnO_2) electron transport layer (ETL) has been widelyemployed to fabricate high-performance perovskite solar cells (PSCs). It hasbeen reported that carbon quantum dots (CQDs) can be used to enhanceelectron mobility of SnO2. However, an in-depth understanding of the drivingforce in this process is still lacking. Here, a high-angle annular dark-fieldscanning transmission electron microscope (HAADF-STEM) is employed, forthe first time, to reveal the SnO_2 crystal face changes with one new type ofCQD doping. Synchrotron-based grazing incidence wide-angle X-rayscattering (GIWAXS) can penetrate the flexible substrate to detect the buriedregion of the perovskite layer, showing the crystallinity and phase purity of theperovskite are significantly improved with CQD-modified SnO_2. The flexiblen-i-p PSCs delivers a power conversion efficiency (PCE) up to 23.57%(22.75%, certificated), which is one of the highest values for single-junctionn-i-p flexible PSCs. The corresponding n-i-p flexible modules achieve a PCE of17.79% with aperture area ～ 24 cm~2. Furthermore, the flexible PSCs showexcellent stability, preserving ≈95% of their initial efficiency after 1200 h under40% relative humidity and 1-sun light irradiation at 25 ℃, and maintained >90% of initial efficiency after 2500 bending cycles at a bending radius of 6 mm.