A fluorine-containing hydrophobic Lewis acid is employed as an effective dopant for PTAA to replace state-of-the-art Li-TFSI/t-BP in PSCs.

In perovskite solar cells (PSCs), the interfaces of the halide perovskite/electron transport layer (ETL) and ETL/metal oxide electrode (MOE) always attract and trap free carriers via the surface electrostatic force, altering quasi‐Fermi level (EFq) splitting of contact interfaces, and significantly limit the charge extraction efficiency and intrinsic stability of devices. Herein, a graded “bridge” is first reported to link the MOE and perovskite interfaces by self vertical phase separation doping (PSD), diminishing the side effect of notorious ionic defects via both reinforced interface Ebi and the vacancies filling. Experimental and theoretical results prove that the inhomogeneous distribution of CsF in the bulk or surface of PC61BM would not only form metal–oxygen (M–O) dipole on MOE, reinforcing the interface Ebi, but also create a graded energy bridge to alleviate the disadvantage of band offset raised by the enhanced interface Ebi, which significantly avoid the carrier accumulation and recombination at defective interfaces. Employing PSD, the power conversion efficiency of the devices approaches 21% with a high open‐circuit voltage (1.148 V) and delivers a high stability of 89% after aging 60 days in atmosphere without encapsulation, which is the highest efficiency of organic electron transport layers for n–i–p PSCs.

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Two asymmetric three-dimensional (3D) holetransporting materials (HTMs) containing a triphenylethylene core and peripheral diphenylamine/triphenylamine moieties are first synthesized and successfully used in perovskite solar cells (PSCs). Both HTMs are obtained from facile preparation procedures and simple purification techniques. The X-ray diffraction, aggregation-induced emission properties, absorption and emission spectra, electrochemical properties, thermal stability, density functional theory calculations, hole mobility, scanning electronic microscopy, atomic force microscopy, steady-state and time-resolved photoluminescence, water contact angles, and photovoltaic parameters of the PSCs are compared. The highest power conversion efficiency increases from 12.57% (CJ-02) to 18.56% (CJ-01), rivaling that obtained from the state-of-the-art 2,2′,7,7′-tetrakis(N,N-di-p-methoxyphenylamine)-9,9′-spirobifluorene (spiro-OMeTAD) (18.69%). Further, the lab synthetic cost of CJ-01 is only about 15.5% of the price of commercial spiro-OMeTAD, and the concentration of CJ-01 solution for device fabrication is less than half of the concentration of spiro-OMeTAD solution (30.0 vs 72.3 mg mL −1 ). These results demonstrate that the propeller-shaped compounds with a highly twisted conformation are readily available and promising alternative HTMs for PSCs. Moreover, an applicable strategy to design new HTMs with 3D structure for achieving highly efficient PSCs is proposed.

The under-coordinated defects within perovskite and its relevant interfaces always attract and trap the free carriers via the electrostatic force, significantly limiting the charge extraction efficiency and the intrinsic stability of perovskite solar cells (PSCs). Herein, self-diffusion interfacial doping by using ionic potassium L-aspartate (PL-A) is first reported to restrain the carrier trap induced recombination via the reconstruction of energy level structure at SnO 2 /perovskite interface in conventional n-i-p structured PSCs. Experiments and theories are consistent with the PL-A anions that can remain at the SnO 2 surface due to strong chemical adsorption. During the spin-coating of the perovskite film, the cations gradually diffuse into perovskite and endow an n-doping effect, which provides higher force and a better energy level alignment for the carrier transport. As a result, they obtained 23.74% power conversion efficiency for the PL-A modified small-area devices, with dramatically improved open-circuit voltage of 1.19 V. The corresponding large-area devices (1.05 cm 2 ) achieved an efficiency of 22.23%. Furthermore, the modified devices exhibited negligible hysteresis and enhanced ambient air stability exceeding 1500 h.

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