We report organic solar cells with a photonic crystal nanostructure embossed in the photoactive bulk heterojunction layer, a topography that exhibits a 3-fold enhancement of the absorption in specific regions of the solar spectrum in part through multiple excitation resonances. The photonic crystal geometry is fabricated using a materials-agnostic process called PRINT wherein highly ordered arrays of nanoscale features are readily made in a single processing step over wide areas (∼4 cm 2 ) that is scalable. We show efficiency improvements of ∼70% that result not only from greater absorption, but also from electrical enhancements. The methodology is generally applicable to organic solar cells and the experimental findings reported in our manuscript corroborate theoretical expectations.Incommensurate length scales conspire to degrade photovoltaic efficiencies in organic solar cells. Exciton diffusion lengths (∼10 nm) are an order of magnitude smaller than absorption lengths. 1,2 This discrepancy is ameliorated by coprecipitating a bicontinuous donor and acceptor phase, a disordered bulk heterojunction (BHJ), 1,3 but inherent disadvantages persist: low exciton dissociation probability, 4 mismatched band gaps, 5 and optical losses. 6 Optimized BHJ devices have active layer thicknesses of ∼100 nm due to the device-limiting trade-off between optical absorption and electrical performance. 7,8 These thicknesses are adequate to absorb most photons in the visible range of the solar spectrum due to the strong extinction coefficient of contemporary BHJ materials. 2,9 However, the sun's maximum photon flux is located around λ ) 700 nm, which is near the band edge of many BHJ materials where absorption is weak. Energy-level engineering via custom synthesis 5 has produced so-called low-bandgap polymers 10 that exhibit broader absorption tails but are located further toward the near-infrared. The active layer thickness constraints imposed on BHJ solar cells make it imperative to develop innovative ways to enhance absorption in a specific spectral range with weak absorption without increasing photoactive layer thickness.Light trapping schemes based on ray optics have provided enhancement in optical absorption, e.g. collector mirrors, 11 microprism substrates, 12 and V-folded configurations, 13 but in these schemes absorption enhancement was not tailored to a desired spectral range. Methods based on wave optics have shown greater promise, and both diffraction gratings [14][15][16] and photonic crystal (PC) designs have been investigated. In particular, theoretical considerations of PC geometries suggest efficiency improvements would be anticipated [17][18][19] for organic solar cells similar to theoretical work on inorganic devices. 20,21 In spite of this theoretical promise, there has been little progress in experimentally demonstrating PC effects in organic solar cells. While there has been success in nanopatterning the photoactive layer, the primary intention has been to provide an undulating surface for evaporating a ...

Efficient charge separation and light absorption are crucial for solar energy conversion over solid photocatalysts. This paper describes the construction of Pt@TiO @In O @MnO mesoporous hollow spheres (PTIM-MSs) for highly efficient photocatalytic oxidation. TiO -In O double-layered shells were selectively decorated with Pt nanoparticles and MnO on the inner and outer surfaces, respectively. The spatially separated cocatalysts drive electrons and holes near the surface to flow in opposite directions, while the thin heterogeneous shell separates the charges generated in the bulk phase. The synergy between the thin heterojunctions and the spatially separated cocatalysts can simultaneously reduce bulk and surface/subsurface recombination. In O also serves as a sensitizer to enhance light absorption. The PTIM-MSs exhibit high photocatalytic activity for both water and alcohol oxidation.

A porous diamond network with three-dimensionally interconnected pores is of technical importance but difficult to be produced. In this contribution, we demonstrate a simple, controllable, and "template-free" approach to fabricate diamond networks. It combines the deposition of diamond/β-SiC nanocomposite film with a wet-chemical selective etching of the β-SiC phase. The porosity of these networks was tuned from 15 to 68%, determined by the ratio of the β-SiC phase in the composite films. The electrochemical working potential and the reactivity of redox probes on the diamond networks are similar to those of a flat nanocrystalline diamond film, while their surface areas are hundreds of times larger than that of a flat diamond film (e.g., 490-fold enhancement for a 3 μm thick diamond network). The marriage of the unprecedented physical/chemical features of diamond with inherent advantages of the porous structure makes the diamond network a potential candidate for various applications such as water treatment, energy conversion (batteries or fuel cells), and storage (capacitors), as well as electrochemical and biochemical sensing.