Blade‐Coated Carbon Electrode Perovskite Solar Cells to Exceed 20% Efficiency Through Protective Buffer Layers

Perovskite solar cells with carbon electrode have a commercial impact because of their facile scalability, low‐cost, and stability. In these devices, it remains a challenge to design an efficient hole transport layer (HTL) for robust interfacing with perovskite on one side and carbon on another. Herein, an organic/inorganic double planar HTL is constructed based on polythiophene (P3HT) and nickel oxide (NiOx) nanoparticles to address the named challenge. Through adding an alkyl ammonium bromide (CTAB) modified NiOx nanoparticle layer on P3HT, the planar HTL achieves a cascade type‐II energy level alignment at the perovskite/HTL interfaces and a preferential ohmic contact at NiOx/carbon electrode, which greatly benefits in charge collection while suppressing charge transfer recombination. Besides, compared with the single P3HT layer, the planar composite enables a robust interfacial contact by protecting perovskite from being corroded by carbon paste during fabrication. As a result, the blade‐coated FA0.6MA0.4PbI3 perovskite solar cells (fabricated in ambient air in fume hood) with carbon electrode deliver an efficiency of 20.14%, the highest value for bladed coated carbon and perovskite solar cells, and withstand 275 h maximum power point tracking in air without encapsulation (95% efficiency retained). Hole transport layer (HTL) is of great importance to carbon electrode perovskite solar cells. This study develops an organic/inorganic HTL bilayer to enhance electrical and mechanical contact at anode buffer interfaces. The modified HTL delivers a state‐of‐the‐art efficiency of 20.8% for perovskite solar cells with both blade‐coated active layer and carbon electrode.