Low Temperature Processed Highly Efficient Hole-Transport-Layer Free Carbon-based Planar Perovskite Solar Cells with SnO2 Quantum Dot Electron-Transport-Layer

The use of expensive hole transport layers (HTLs) and back contact along with the stability issue of perovskite solar cells (PSCs) has been a detrimental factor when it comes to commercialization of the technology. In addition, high temperature and long annealing time processed electron transport layers (ETLs, e.g. TiO2) prevent the flexible solar cell application in most polymer substrates. Herein, we opted for HTL-free carbon electrodes owing to their low-cost production and superior stability in air, compared with their noble metal counterparts. In this work, we fabricate planar PSCs using low-temperature solution processed SnO2 quantum dots (QDs) as ETLs, which offers significant advantages over high-temperature processed ETLs because of its excellent electron extraction and hole blocking ability. In addition, by integrating a low-cost and stable carbon electrode, an impressive energy conversion efficiency of 13.64% with a device architecture glass/In doped SnO2/QD-SnO2/perovskite/carbon under 1 sun illumination at ambient conditions have been achieved. This work paves the way to achieve fully low-temperature processed printable PSCs at an affordable cost by integrating the QD SnO2 ETL and carbon electrodes.