A series of metal acetylacetonates produced by a full low-temperature (below 100 °C) process are successfully employed to obtain both "multistable" and high-performance planar-inverted perovskite solar cells. All the three kinds of champion cells in small area exhibit over 18% in conversion-efficiency with negligible hysteresis, along with a conversion efficiency above 16% for planar PSCs in an aperture area of over 1 cm .

Molecular doping of inorganic semiconductors is a rising topic in the field of organic/inorganic hybrid electronics. However, it is difficult to find dopant molecules which simultaneously exhibit strong reducibility and stability in ambient atmosphere, which are needed for n‐type doping of oxide semiconductors. Herein, successful n‐type doping of SnO2 is demonstrated by a simple, air‐robust, and cost‐effective triphenylphosphine oxide molecule. Strikingly, it is discovered that electrons are transferred from the R3P+O−σ‐bond to the peripheral tin atoms other than the directly interacted ones at the surface. That means those electrons are delocalized. The course is verified by multi‐photophysical characterizations. This doping effect accounts for the enhancement of conductivity and the decline of work function of SnO2, which enlarges the built‐in field from 0.01 to 0.07 eV and decreases the energy barrier from 0.55 to 0.39 eV at the SnO2/perovskite interface enabling an increase in the conversion efficiency of perovskite solar cells from 19.01% to 20.69%.

The environmentally friendly additive 2,2,2‐trifluoroethylamine hydrochloride (TFEACl) is used in synergy with SnF2 to enhance the efficiency and stability of FASnI3‐based solar cells. Both TFEA+ and Cl− are present in the films, but only Cl− is incorporated into the crystal lattice of the perovskite. The addition of TFEACl suppresses the segregation of SnF2, resulting in improvements in film morphology, in addition to a more favorable energy band alignment, and improved suppression of the formation of Sn4+. Consequently, reduced charge recombination and improved charge collection result in an efficiency enhancement from 3.63 to 5.30%. The stability of the devices is also significantly enhanced, with devices with TFEACl retaining over 60% of initial PCE after 350 h of light soaking in ambient, while devices without TFEACl experience failure in 120 h under the same testing condition.

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