Organic−inorganic hybrid perovskites have become one of the most promising thin-film solar cell materials owing to their remarkable photovoltaic properties. However, nonradiative recombination of carriers usually leads to inferior performance of perovskite (PVK) devices. Interface modification is one of the effective ways to improve separation of charges for perovskite solar cells (PSCs). Here, a small organic molecule of tetrafluorophthalonitrile (TFPN) is used to enhance the extraction and transportation of carriers at the PVK/hole transport layer (HTL) interface. The electron-rich C−F group effectively reduces the trap state density in the perovskite through chemical combination with the empty orbital of Pb 2+ or other electron traps on the PVK surface, resulting in enhanced interface contact between the PVK and HTL. Meanwhile, the CN group in TFPN also inactivates the defects caused by Pb 2+ . The Fermi level of the perovskite shifts by 0.15 eV to its valence band due to the strong electron acceptor nature of the F atom, indicating that positive dipoles and p-type doping emerge, which validly suppress the recombination of carriers for the PVK film. Therefore, the optimized PSC shows the highest power conversion efficiency (PCE) of 22.82% compared to 19.40% for the control one. The champion FF reaches up to 81.2% (PCE 21.44%) due to the effectively enhanced carrier separation. In addition, the unencapsulated device shows enhanced stability under air conditions.

Graphene nanosheets have been synthesized from commercial expandable graphite by heating in a microwave oven and dispersing in ethanol by ultrasonication. Scanning and transmission electron microscopy and electron energy-loss spectroscopy and atomic force microscope showed that the nanosheets were about 2 nm in thickness and 10 microm in diameter. The field emission of the graphene sheets has been investigated. An emission current density of 1 mA/cm2 has been achieved at an electric field of 3.7 V/microm with a turn-on field of 1.7 V/microm at 0.01 mA/cm2. The annealing of the samples at 400 degrees C in vacuum greatly improved the field emission performance.

Intrinsic defects are key factors that would affect the performance and stability of perovskite solar cells (PSCs). Herein, a sulfonamides additive, methyl 3‐sulfamoyl‐2‐thiophenecarboxylate (MSTC), is introduced into the PbI2 or FAI/MACl/MABr precursor solution, to prepare high‐quality PSCs with a two‐step method. After the addition of MSTC, all the devices show enhanced performance. With optimized MSTC incorporated into PSCs, the champion power conversion efficiency (PCE) of the PSCs is increased from 19.19% to 22.14%, and the stability is also improved. The MSTC‐FAI based device can still maintain 89% of its initial PCE compared to 68% of the control one after 15 days in ambient condition under relative humidity of 40–50% at room temperature in dark. Test results reveal that amido group in MSTC would coordinate with PbI2 or FAI through hydrogen bonding (NH···I), thus effectively enhancing the performance of devices. Nevertheless, the sulfonyl and carbonyl groups in MSTC would coordinate with the FAI precursor through chemical bond of COS and COC. And with the hydrogen bonding connection between MSTC and FAI, the inherent defects in the MSTC‐FAI based device are effectively suppressed, leading to the enhanced photovoltaic performance.

As a superstars of photovoltaic devices, organic–inorganic hybrid perovskite solar cells (PSCs) have garnered plenty of interest due to their superior character. However, many defects, such as carrier recombination, inferior stability, poor interface contact, have prevented their further development. Here, we demonstrate a novel approach of interface engineering to form a compact perovskite layer with decreased defects on SnO2 film by adding tris­(pentafluorophenyl)­boron (TPFPB) as an interfacial modification layer, which validly improves the interface performance and enhances the crystallinity of MAPbI3. Hence the planar MAPbI3 PSCs with TPFPB modification show fast charge transfer and low trap state density with an enhanced champion power conversion efficiency (PCE) from the original of 16.92% to 19.41%, as well as long-term stability with 80.7% of its initial PCE after 1000 h of aging in N2 atmosphere without encapsulation, while the pristine one only shows 68.9% of the original PCE. The results reveal that TPFPB can be used as an effective interface modification layer for high efficiency and stability PSCs, and it maybe also be used in other devices due to its superior interface modification for high quality crystallinity thin films.

Structural, magnetic and transport properties were investigated for heterogeneous (FexSn1−x)1−y(SiO2)y films deposited on oxidized silicon substrates at room temperature with RF magnetron sputtering. X-ray diffraction indicated that the films consist of a nanocrystalline phase of FeSn2 embedded into an amorphous background. For (FexSn1−x)92.33(SiO2)7.67, it was demonstrated that with the increase in the Fe component an evolution from negative isotropic magnetoresistance (MR) behaviour to one with a mixture of anisotropic magnetoresistance and isotropic negative MR occurs. On fixing the SiO2 percentage and decreasing the Fe–Sn ratio, the negative transverse MR first increases and then decreases. For samples having a fixed Fe–Sn ratio, the negative transverse MR increases with the increase in SiO2. Compared with the Fe–Sn system, the addition of 7.67 at.% SiO2 enhances the saturated Hall resistivity. Further increase in SiO2 introduces a complicated saturated Hall resistivity dependence on the concentration of SiO2.