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 (SnO2) electron transport layer (ETL) and Zn-TFSI2 doped spiro-OMeTAD hole transport layer (HTL). Apparently, the incorporation of Ru drastically shifts the Fermi level of SnO2 ETL upward, which provides a facile route to tailor the ETL/perovskite band-offset to improve built-in electric fields of devices for improving VOC 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 SnO2 is employed as ETL. On the other hand, the conception of Zn-TFSI2 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 JSC of 24.6 mA cm-2, VOC 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.