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Excess PbI2 has been deemed as indispensable component to boost the efficiency of perovskite solar cells (PSCs). However, the random aggregation of PbI2 crystals seriously disturbs the transport behavior of the carrier and accelerates the degradation of perovskite film. Herein, an effective strategy to in situ disperse excess PbI2 crystals via the columnar liquid crystal (T6TE) is developed. Rapid self‐assembly induced by intermolecular π–π interaction enables T6TE to form the ordered columnar phase with "edge‐on" orientation in perovskite. The columnar T6TE can efficiently disperse excess PbI2 crystals with the merits of strong negative electrostatic potential and highly steric hindrance. Target perovskite deserves preferable crystallization and reconstructed surface, leading to reduced defects density, less residual stress, and efficient carrier transport. Besides, the T6TE significantly impedes the degradation of perovskite film and the formation of Pb0 defects. Resultant T6TE‐assisted PSCs achieve the champion power conversion efficiency (PCE) of 24.27% for mixed Cs+‐FA+‐MA+ perovskite. The PCE of a larger area (1 cm2) device reaches to 21.50%. The unencapsulated device maintains ≈85% of the initial PCE after 1500 h storage in the atmosphere with 40–60% relative humidity. This work provides a new strategy to in situ disperse excess PbI2 by incorporating columnar liquid crystal for the first time. [ABSTRACT FROM AUTHOR]

A fan-structure piezoelectric energy harvester was proposed and tested in order to collect wind energy. Polyvinylidene fluoride was chosen due to its flexibility and longevity when compared to lead zirconate titanate. The impact-induced piezoelectric energy harvester consists of a stator and a rotor and a circular array of four cantilevers, utilize the rotor blades’ periodic impact on the free end of the cantilevers to generate oscillatory motion of cantilevers. A circular array of polyvinylidene fluoride cantilevers was fixed around the rotor in order to increase output power, save space at the same time. Static and transient characteristics of different cantilevers were investigated using finite element method and the result showed that polyvinylidene fluoride triangular cantilever performs the best in output voltage and power. Under the condition of optimal impedance and optimal overlap distance, a sum AC output power of four cantilevers without connection to each other approach to 0.75 mW was measured at the wind speed of 7 m/s when the blade number of rotor is 7 or 9. Two branches 0.27 mW DC output power was obtained when each two cantilevers in parallel connection in the case of full-wave rectification of each cantilever at the wind speed of 7 m/s. [ABSTRACT FROM AUTHOR]