Synergistic Enhancement of Efficient Perovskite/Quantum Dot Tandem Solar Cells Based on Transparent Electrode and Band Alignment Engineering

Perovskite-based tandem solar cells have demonstrated high potential for overcoming the Shockley-Queisser limit. Routine bandgap (RBG, approximate to 1.55 eV) perovskites have achieved a perfect balance between efficiency and stability. The narrow bandgap (NBG) candidates for RBG perovskite-based tandem devices are very limited. Lead sulfide (PbS) colloidal quantum dots (CQDs) are a promising partner due to their broad absorption spectra. However, the efficiency of RBG perovskite/QD tandem devices still lags behind. Herein, efficient RBG perovskite/QDs four-terminal tandem photovoltaics are successfully implemented through synergistic enhancement from transparent electrode and band alignment Engineering. For tin doped indium oxide (ITO) electrodes, their conductivity and near-infrared transparency are leveraged using magnetron sputtering and reactive plasma deposition (RPD) methods. Furthermore, instead of traditional zinc oxide, aluminum-doped zinc oxide (AZO) is developed to enhance the carrier extraction capability of PbS QD bottom cells. Based on the above enhancements, approximate to 0.95 eV PbS solar cells achieve a record efficiency of 14.14%. Integrated with the front semi-transparent perovskite solar cells, the four-terminal perovskite/QD tandem device reaches a record efficiency of 26.12%. The synergistic combination of the RBG perovskite and NBG QD devices provides promising prospects for tandem photovoltaics. Routine bandgap perovskite (approximate to 1.55 eV) and PbS quantum dot (approximate to 0.95 eV) four-terminal tandem photovoltaics are reported. Quantum dot solar cells achieve a record efficiency of 14.14% based on transparent electrode and band alignment engineering. The four-terminal tandem solar cells achieve an efficiency of 26.12%. The authors provide a new avenue for perovskite-based tandem photovoltaics. image