Lead-free metal halide perovskites have attracted extensive attention as a promising optoelectronic semiconductor with environmental friendliness. Cs2SnI6, a double perovskite with both good phase and composition stability, is an appealing...

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).

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Carbon-based all-inorganic CsPbI x Br3–x perovskite solar cells offer high stability against heat and humidity and a suitable band gap for tandem and semitransparent photovoltaics. In CsPbI x Br3–x perovskite films, the defects at grain boundaries (GBs) cause charge trapping, reducing the efficiency of the cell. Electronic deactivation of GB has been a conventional strategy to suppress the trapping, but at the cost of charge carrier transport through the boundaries. Here, we turn the GBs into benign charge transport pathways with the aid of bipolar charge transport semiconductors, namely, Ti3C2T X (MXene) and Spiro-OMeTAD, respectively. Thanks to the synergistic effects of both n- and p-type transport media, the charge transport is improved and balanced at the GBs. As a result, the cells achieve an efficiency of 12.7%, the highest among all low-temperature-processed carbon-based inorganic perovskite solar cells. Benign GBs also lead to enhanced light and aging stabilities. Our work demonstrates a proof-of-concept strategy of benign electronic modulation of GBs for solution-processed perovskite solar cells.