CdS as Electron Transport Layer for Low‐Hysteresis Perovskite Solar Cells

In order to achieve highly efficient perovskite solar cells in n–i–p geometry with little hysteresis, CdS is investigated as low‐cost, easily processable electron transport layer (ETL). For comparison, also perovskite solar cells without ETL or with low‐temperature processed compact TiO x as well as combinations of TiO x and CdS in dual layer ETLs are investigated. It is found that CdS strongly suppresses hysteresis and that even inverted hysteresis can occur, caused by the much higher electron mobility of CdS in comparison to TiO x . Additionally, SIMS depth profiles reveal that iodide diffusion is suppressed when CdS instead of TiO x is in contact to the perovskite layer. For cells which are processed in ambient atmosphere, a highest efficiency with CdS as ETL >10% with minimal hysteresis is achieved.