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A novel bio-based composite material, suitable for electronic as well as automotive and aeronautical applications, was developed from soybean oils and keratin feather fibers (KF). This environmentally friendly, low-cost composite can be a substitute for petroleum-based composite materials. Keratin fibers are a hollow, light, and tough material and are compatible with several soybean (S) resins, such as acrylated epoxidized soybean oil (AESO). The new KFS lightweight composites have a density Ϸ 1 g/cm 3 , when the KF volume fraction is 30%. The hollow keratin fibers were not filled by resin infusion and the composite retained a significant volume of air in the hollow structure of the fibers. Due to the retained air, the dielectric constant, k, of the composite material was in the range of 1.7-2.7, depending on the fiber volume fraction, and these values are significantly lower than the conventional silicon dioxide or epoxy, or polymer dielectric insulators. The coefficient of thermal expansion (CTE) of the 30 wt % composite was 67.4 ppm/°C; this value is low enough for electronic application and similar to the value of silicon materials or polyimides used in printed circuit boards. The water absorption of the AESO polymer was 0.5 wt % at equilibrium and the diffusion coefficient in the KFS composites was dependent on the keratin fiber content. The incorporation of keratin fibers in the soy oil polymer enhanced the mechanical properties such as storage modulus, fracture toughness, and flexural properties, ca. 100% increase at 30 vol %. The fracture energy of a single keratin fiber in the composite was determined to be about 3 kJ/m 2 with a fracture stress of about 100 -200 MPa. Considerable improvements in the KFS composite properties should be possible by optimization of the resin structure and fiber selection.

Due to its excellent thermal stability and high performance, inorganic cesium lead mixed halide (ABX3, where A = Cs, B = Pb, and X = I/Br) all‐inorganic perovskite solar cells (IPVSCs) have attracted much interest in optoelectronic applications. However, the film quality, enough absorption by desired film thickness, and nature of partial replacement of cations determine the stability of the CsPbI2Br perovskite films. Herein, a hot air method is used to control the thickness and morphology of the CsPbI2Br perovskite thin film, and the A‐site (herein, Cs+) cation is partially incorporated by rubidium (Rb+) cations for making the stable black phase under ambient conditions. The Rb cation‐incorporated Cs1−xRbxPbI2Br (x = 0–0.03) perovskite thin films exhibit high crystallinity, uniform grains, extremely dense, and pinhole‐free morphology. The fabricated device with its Cs0.99Rb0.01PbI2Br perovskite composition with poly(3‐hexylthiophene‐2,5‐diyl) as a hole‐transporting layer exhibits a power conversion efficiency (PCE) of 17.16%, which is much higher than that of CsPbI2Br‐based IPVSCs. The fabricated Cs0.99Rb0.01PbI2Br‐based IPVSC devices retain >90% of the initial efficiency over 120 h at 65 °C thermal stress, which is much higher than that of CsPbI2Br samples.

Replacement of conventional organic cations by thermally stable inorganic cations in perovskite solar cells (PSCs) is one of the promising approaches to make thermally stable photovoltaics. However, conventional spin-coating and solvent-engineering processes in a controlled inert atmosphere hamper the upscaling. In this study, we demonstrated a dynamic hot-air (DHA) casting process to control the morphology and stability of all-inorganic PSCs which is processed under ambient conditions and free from conventional harmful antisolvents. Furthermore, CsPbI2Br perovskite was doped with barium (Ba2+) alkaline earth metal cations (BaI2:CsPbI2Br). This DHA method facilitates the formation of uniform grain and controlled crystallization that makes stable all-inorganic PSCs which enables an intact black α-phase under ambient conditions. The DHA-processed BaI2:CsPbI2Br perovskite photovoltaics shows the champion power conversion efficiency (PCE) of 14.85% (reverse scan) for a small exposure area of 0.09 cm2 and 13.78% for a large area of 1 × 1 cm2 with excellent reproducibility. Interestingly, the hot-air-processed devices retain >92% of the initial efficiency after 300 h. This DHA method facilitates a wide processing window for upscaling the all-inorganic perovskite photovoltaics.

We have demonstrated organometallic perovskite solar cells (PSCs) based on Au decorated TiO2 nanofibers and methylammonium lead iodide (MAPbI3). A power conversion efficiency of 14.92% was achieved, which is significantly higher than that of conventional mesoporous (mp) TiO2, as well as TiO2 nanofiber-based devices. The present synthetic process provides new opportunities for the development of efficient plasmonic PSCs based on metal oxide nanofibers. Solar cells based on these architectures exhibit a short-circuit current density J(SC) of 21.63 ± 0.36 mA cm(-2), V(OC) of 0.986 ± 0.01 V and fill factor of 70% ± 3%, which provide a power conversion efficiency of 14.92% ± 0.33% under standard AM 1.5 conditions. The results of time-resolved photoluminescence (TRPL) spectroscopy and solid-state impedance spectroscopy (ssIS) revealed that PSCs based on Au-decorated TiO2 nanofibers exhibit a low recombination rate. The present results are much higher than those for reported PSCs based on a Au@TiO2 electron-transporting layer (ETL).

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Mixed-halide CsPbI 2 Br perovskite is promising for efficient and thermally stable all-inorganic solar cells; however, the use of conventional antisolvent methods and additives-based hole-transporting layers (HTLs) currently hampers progress. Here, we have employed hot-air-assisted perovskite deposition in ambient condition to obtain high-quality photoactive CsPbI 2 Br perovskite films and have extended stable device operation using metal cation doping and dopant-free hole-transporting materials. Density functional theory calculations are used to study the structural and optoelectronic properties of the CsPbI 2 Br perovskite when it is doped with metal cations Eu 2+ and In 3+ . We experimentally incorporated Eu 2+ and In 3+ metal ions into CsPbI 2 Br films and applied dopant-free copper(I) thiocyanate (CuSCN) and poly(3-hexylthiophene) (P3HT)-based materials as low-cost hole transporting layers, leading to record-high power conversion efficiencies of 15.27% and 15.69%, respectively, and a retention of >95% of the initial efficiency over 1600 h at 85 °C thermal stress.

In the current work, we studied the effect of the passivation of atomic layer deposited (ALD) ultrathin TiO2 on hydrothermally grown one-dimensional (1D) TiO2 nanorod (NR) arrays for solid-state perovskite-sensitized solar cells. Different thicknesses of ALD-passivated TiO2 were deposited on the hydrothermally grown 1D TiO2 NR samples. The ALD TiO2 thickness was varied from 1 to 5 nm by variation of the growth cycle. Our controlled results revealed that the 4 nm thin-layer-passivated TiO2 NR sample shows a power conversion efficiency (PCE) as high as η = 12.53% (without masking) for the CH3NH3PbI3 perovskite absorbing layer. Our results revealed that the solar cell performance with different ALD passivation thicknesses strongly affects the open-circuit voltage (V OC) as well as the short-circuit current density (J SC). However, compared with high-temperature-processed standard device configurations based on TiCl4-treated mesoporous TiO2 (mp-TiO2) (∼10%) and TiCl4-treated TiO2 NR (∼9%) perovskite solar cells, our low-temperature-processed, pinhole-free ALD-passivated devices exhibit higher PCEs. The 4 nm passivated sample exhibits η = 12.53 ± 0.35% with J SC = 19.23 ± 0.53 mA cm–2, fill factor (FF) = 0.70 ± 0.4, and V OC = 0.931 ± 0.01 V. By control of the ultrathin passivation layer thickness, our champion cell with 4.8 nm ALD passivated TiO2 NRs demonstrated a PCE of 13.45% with J SC = 19.78 mA cm–2, V OC = 0.945 V, and FF = 0.72. These results further emphasize hydrothermally grown 1D TiO2 and ALD-passivated electron transporting layers (ETLs) for efficient perovskite solar cell applications.