Free-Standing High Surface Area Titania Films Grown at the Air–Water Interface

Free-standing titania films were grown at the air–water interface, a novel method to synthesize robust TiO₂ nanowire/nanoparticle composite films. The calcined films contain an anatase crystal phase and have a high surface area with a structure composed of one-dimensional long nanowires and mesoporous nanoparticle branches. These suggest a promising way to manufacture large areas of thick porous titania films for many applications. As one possible application, use of these films in a dye-sensitized solar cell demonstrates the potential of these materials

Efficient Compact-Layer-Free, Hole-Conductor-Free, Fully Printable Mesoscopic Perovskite Solar Cell

A compact-layer-free, hole-conductor-free, fully printable mesoscopic perovskite solar cell presents a power conversion efficiency of over 13%, which is comparable to that of the device with a TiO₂ compact layer. The different wettability of the perovskite precursor solution on the surface of FTO and TiO₂ possesses a significant effect on realizing efficient mesoscopic perovskite solar cell. This result shows a promising future in printable solar cells by further simplifying the fabrication process and lowering the preparation costs

Surface Evolution of PtCu Alloy Shell over Pd Nanocrystals Leads to Superior Hydrogen Evolution and Oxygen Reduction Reactions

Pt-based electrocatalysts are by far the most effective for the hydrogen evolution reaction (HER) and oxygen reduction reaction (ORR), but they still suffer from high cost and insufficient overall performance. Improving Pt utilization via alloying or by forming core@shell structures is important for enhancing Pt activity and overall electrocatalytic performance. Herein, we report a simple seed-mediated method for synthesizing a dodecahedral PtCu alloy atomic shell on Pd nanocrystals. Significantly, such a Pd@PtCu nanocomposite with unique core@alloy-shell structure achieves a 25-fold and 6-fold enhancement of mass activity for HER and ORR, respectively, compared with the commercial Pt/C catalyst in acid media. Moreover, the unique Pd@PtCu catalyst shows only 1.0 mV increase in overpotential at 10 mA cm^–2 after 10 000 cycles for HER and almost no activity decay after 5 000 cycles for ORR, indicating the high endurance of Pd@PtCu in the electrochemical environment

The Influence of the Work Function of Hybrid Carbon Electrodes on Printable Mesoscopic Perovskite Solar Cells

In printable mesoscopic perovskite solar cells (PSCs), carbon electrodes play a significant role in charge extraction and transport, influencing the overall device performance. The work function and electrical conductivity of the carbon electrodes mainly affect the open-circuit voltage (<i>V</i>_OC) and series resistance (<i>R</i>_s) of the device. In this paper, we propose a hybrid carbon electrode based on a high-temperature mesoporous carbon (m-C) layer and a low-temperature highly conductive carbon (c-C) layer. The m-C layer has a high work function and large surface area and is mainly responsible for charge extraction. The c-C layer has a high conductivity and is responsible for charge transport. The work function of the m-C layer was tuned by adding different amounts of NiO, and at the same time, the conductivities of the hybrid carbon electrodes were maintained by the c-C layer. It was supposed that the increase of the work function of the carbon electrode can enhance the <i>V</i>_OC of printable mesoscopic PSCs. Here, we found the <i>V</i>_OC of the device based on hybrid carbon electrodes can be enhanced remarkably when the insulating layer has a relatively small thickness (500–1000 nm). An optimal improvement in <i>V</i>_OC of up to 90 mV could be achieved when the work function of the m-C was increased from 4.94 to 5.04 eV. When the thickness of the insulating layer was increased to ∼3000 nm, the variation of <i>V</i>_OC as the work function of m-C increased became less distinct

Boron-Doped Graphite for High Work Function Carbon Electrode in Printable Hole-Conductor-Free Mesoscopic Perovskite Solar Cells

Work function of carbon electrodes is critical in obtaining high open-circuit voltage as well as high device performance for carbon-based perovskite solar cells. Herein, we propose a novel strategy to upshift work function of carbon electrode by incorporating boron atom into graphite lattice and employ it in printable hole-conductor-free mesoscopic perovskite solar cells. The high-work-function boron-doped carbon electrode facilitates hole extraction from perovskite as verified by photoluminescence. Meanwhile, the carbon electrode is endowed with an improved conductivity because of a higher graphitization carbon of boron-doped graphite. These advantages of the boron-doped carbon electrode result in a low charge transfer resistance at carbon/perovskite interface and an extended carrier recombination lifetime. Together with the merit of both high work function and conductivity, the power conversion efficiency of hole-conductor-free mesoscopic perovskite solar cells is increased from 12.4% for the pristine graphite electrode-based cells to 13.6% for the boron-doped graphite electrode-based cells with an enhanced open-circuit voltage and fill factor