Hysteresis-Free Planar Perovskite Solar Cells with a Breakthrough Efficiency of 22% and Superior Operational Stability over 2000 h

Understanding the transport loss and the ways to improving optoelectronic properties of the charge transporting layers is critical to fabricate highly efficient, long-term stable, and hysteresis-free perovskite solar cells (PSCs). Herein, we report success in suppressing hysteresis and boosting the performance of operationally stable planar solar cells using a ruthenium (Ru) doped tin oxide (SnO 2 ) electron transport layer (ETL) and Zn-TFSI 2 doped spiro-OMeTAD hole transport layer (HTL). Apparently, the incorporation of Ru drastically shifts the Fermi level of SnO 2 ETL upward, which provides a facile route to tailor the ETL/perovskite band-offset to improve built-in electric fields of devices for improving V OC and electron extraction simultaneously. Meanwhile, rapid injection of the photogenerated electrons from perovskite into ETL with reduced trap density is also observed when Ru doped SnO 2 is employed as ETL. On the other hand, the conception of Zn-TFSI 2 incorporation into HTL not only further boosts the photovoltaic performance but also prolongs the photostability of the devices. Consequently, a breakthrough efficiency of 22% (average 21.8%) with a J SC of 24.6 mA cm –2, V OC of 1.15 V, and FF of 0.78 has been obtained in planar-type PSCs with a loss in efficiency of only ∼3% at maximum power point tracking over 2000 h.