Visible light-driven photocatalytic hydrogen production using Cu-doped SrTiO ₃

A new Cu-doped SrTiO3 photocatalyst was synthesized and characterized for uses in the visible-light photocatalytic production of hydrogen from water. The photocatalytic activity was assessed based on the characterization of the photocatalysts (band gap energy, surface area, crystallinity, and morphology) and the effects of varying together the calcination temperature, the Cu:Sr mole ratio, and the photocatalyst loading amount. It was determined that the amount of hydrogen evolved was largely dictated by the amount of Cu dopant present in the photocatalysts. The created Box Behnken Design optimization scenarios suggested the conditions: 850°C, 0.01 Cu:Sr, 0.33 g loading as the optimal conditions for maximum hydrogen production holding all studied factors in range, and the conditions: 850°C, 0.01 Cu:Sr, 0.21 g loading as the optimal conditions for the maximum hydrogen production while minimizing Cu dopant and photocatalyst loading.</p

Influence of copolymer interface orientation on the optical emission of polymeric semiconductor heterojunctions.

We have examined the Coulombic interactions at the interface in a blend of two copolymers with intramolecular charge-transfer character and optimized band offsets for photoinduced charge generation. The combination of both time-resolved measurements of photoluminescence, and quantum-chemical modeling of the heterojunction allows us to show that relative orientation across the heterojunction can lead to either a repulsive barrier ( approximately 65 meV) or an attractive interaction which can enhance the charge-transfer processes. We conclude that polymer orientation at the heterojunction can be as important as energy-band offsets in determining the dynamics of charge separation and optical emission

Determining the optimum morphology in high-performance polymer-fullerene organic photovoltaic cells

This work was supported by the Engineering and Physical Sciences Research Council (grant number EP/I013288/1) and from the European Union Seventh Framework Programme under grant agreement 321305.The morphology of bulk heterojunction organic photovoltaic cells defines many of the device performance characteristics. Measuring the morphology is challenging due to the small length scales and low contrast between organic materials. Here we have utilised nanoscale photocurrent mapping, ultrafast fluorescence and exciton diffusion to observe the detailed morphology of a high performance blend. We show that optimised blends consist of elongated fullerene-rich and polymer-rich fibre-like domains which are 10-50 nm wide and 200-400 nm long. These elongated domains provide a concentration gradient for directional charge diffusion which helps extraction of charge pairs with 80% efficiency. In contrast, blends with agglomerated fullerene spheres show a much lower efficiency of charge extraction of ~45% which is attributed to poor electron and hole transport. Our results show that formation of narrow and elongated domains are desirable in bulk heterojunction solar cells.Publisher PDFPeer reviewe