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.