Organic-inorganic perovskite solar cells have seen tremendous developments in recent years. As a hole transport material, 2,2',7,7'-tetrakis( N, N-di- p-methoxyphenylamine)-9,9'-spirobifluorene (Spiro-OMeTAD) is widely used in n-i-p perovskite solar cells. However, it may lead to the perovskite film degradation due to the dopant lithium bis((trifluoromethyl)sulfonyl)amide (Li-TFSI), which has strong hydrophilicity. CuS is considered as a superior p-type transport material, which also has a favorable energy level matching with the highest occupied molecular orbital of Spiro-OMeTAD. Herein, a solution-processed organic-inorganic-integrated hole transport layer was reported, which is composed of the undoped Spiro-OMeTAD and CuS layer. Since there is no Li-TFSI doping, it is extremely conductive to the long-term stability of the solar cells. In the meantime, we proposed a method to adjust the lowest unoccupied molecular orbital (LUMO) of SnO via nitrogen implantation (N:SnO). The LUMO of SnO can be tuned from -4.33 to -3.91 eV, which matches well with the LUMO of CHNHPbI (-3.90 eV), and thus helps to reduce hysteresis. The modified hole and electron transport layers were applied in n-i-p perovskite solar cells, which achieve a maximum power conversion efficiency (PCE) of 17.10 and 96% retention of PCE after 1200 h in air atmosphere without any encapsulation.

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The high-energy ball milling method was adopted to explore the influence of ball milling parameters, such as milling speed and additive amounts of process control agent (PCA) on tungsten powder. The morphology and microstructure of tungsten powder in the process of refinement were characterized by field-emission scanning electron microscope (FE-SEM), field-emission transmission electron microscope (FE-TEM), and X-ray diffractometer (XRD). Results revealed that the ball milling process and the refinement of tungsten particle and grain can be largely influenced by these two parameters. The milling efficiency was found to be highest with the milling speed of 700 rpm and additive amounts of 8% PCA. The mechanisms for the effect of these two parameters and milling time on the refinement process were discussed. Nanocrystalline tungsten powder with a particle size and grain size smaller than 100 nm was obtained, and the grain size of 5-15 nm was fabricated successfully under the highest milling efficiency conditions.

In recent years, perovskite solar cells have drawn a widespread attention. As an electrode material, fluorine-doped tin oxide (FTO) is widely used in various kinds of solar cells. However, the relatively low work function (WF) (∼4.6 eV) limits its application. The potential barrier between the transparent conductive oxide electrode and the hole transport layer (HTL) in inverted perovskite solar cells results in a decrease in device performance. In this paper, we propose a method to adjust WF of FTO by implanting zirconium ions into the FTO surface. The WF of FTO can be precisely and continuously tuned between 4.59 and 5.55 eV through different dopant concentration of zirconium. In the meantime, the modified FTO, which had a WF of 5.1 eV to match well the highest occupied molecular orbital energy level of poly(3,4-ethylenedioxylenethiophene):polystyrene sulfonate, was used as the HTL in inverted planar perovskite solar cells. Compared with the pristine FTO electrode-based device, the open circuit voltage increased from 0.82 to 0.91 V, and the power conversion efficiency increased from 11.6 to 14.0%.