Efficient and Hole-Transporting-Layer-Free CsPbI2Br Planar Heterojunction Perovskite Solar Cells through Rubidium Passivation

Graphical Defect passivation : All-inorganic carbon-based perovskite solar cells (PSCs), with Rb-doped CsPbI 2 Br as the absorber layer, exhibit improved efficiency and enhanced stability compared with PSCs with pristine CsPbI 2 Br owing to the effectiveness of Rb incorporation in passivating defects states. Recently, inorganic perovskite CsPbI 2 Br has gained much attention for photovoltaic applications owing to its excellent thermal stability. However, low device performance and high open-voltage loss, which are the result of its intrinsic trap states, are hindering its progress. Herein, planar CsPbI 2 Br solar cells with enhanced performance and stability were demonstrated by incorporating rubidium (Rb) cations. The Rb-doped CsPbI 2 Br film exhibited excellent crystallinity, pinhole-free surface morphology, and enhanced optical absorbance. By using low-cost carbon electrodes to replace the organic hole-transportation layer and metal electrode, an excellent efficiency of 12 % was achieved with a stabilized efficiency of over 11 % owing to the suppressed trap states and recombination in the CsPbI 2 Br film. Additionally, the annealing temperature for the Rb-doped CsPbI 2 Br film could be as low as 150 °C with a comparable high efficiency over 11 %, which is one of the best efficiencies reported for hole-transporting-layer-free all-inorganic perovskite solar cells. These results could provide new opportunities for high-performance and stable inorganic CsPbI 2 Br solar cells by employing A-site cation substitution.