314 wileyonlinelibrary.com COMMUNICATION www.MaterialsViews.com www.advopticalmat.dePhoton detection and imaging devices for selective use in the ultraviolet (UV) spectral range are of interest for use in applications that include fl ame detection, chemical sensing, astronomical observation, communications and health care. [1][2][3][4][5][6][7][8][9][10] Of particular value are visible-blind and solar-blind UV detectors, with selective responses at wavelengths below 400 nm and 280 nm respectively. [1][2][3] In these detectors, low sensitivities for visible and infrared (IR) light ensure robust measurement capabilities in the UV with minimal background. Traditional UV detectors based on photomultiplier tubes [ 4 ] are attractive but require require bulky, vacuum based components. Recent work shows the ability to form visible-blind and solar-blind UV detectors using large bandgap semiconductors like AlGaN, [ 5 ] diamond, [ 6 ] ZnO [ 7,8 ] and certain organic materials [ 9 ] to provide attractive alternatives. A common disadvantage, however, is that these materials, by comparison to silicon, are diffi cult to grow/deposit in high purity, uniform layers, to dope in controlled ways and/or to process at large areas with low costs. Devices that combine UV bandpass fi lters with silicon detectors avoid these limitations, but they suffer from intrinsically low responses in the UV (effective quantum effi ciency < 30%), limited lifetimes due to degradation under prolonged UV exposure and diffi culties in fabricating the necessary fi lters. [10][11][12][13][14] Some such fi lters use alkali metals, [ 11,13 ] which require advanced packaging structures to prevent oxidation, while others exploit sub-wavelength photonic crystals, [ 14 ] whose fabrication can be diffi cult. Here we present a self-powered, visible-blind UV detection design that exploits Si based photodetectors with UV down-shifting luminophores in structures for light trapping and management. Specifi cally, a europium (Eu) complex dispersed poly(methyl methacrylate) (PMMA) fi lm coated on top of a Si detector serves as a luminescent waveguide to enable selective UV responses from 300 nm to 360 nm. The obtained ratio of photoresponses in the UV (300-360 nm) and the visible (>400 nm) is ∼10 2 -10 3 . Demonstration experiments illustrate the ability of such devices to detect UV emitted from invisible methanol fl ames. A simple imaging system that incorporates 256 multiplexed detectors illustrates the scalability of the ideas.The europium (Eu 3+ ) complex (structure shown as an inset in Figure 1 a), Eu(DPEPO)(hfac) 3 [DPEPO = bis(2-(diphenylphosphino)phenyl)ether oxide, hfac = hexafl uoroacetylacetonate] or EuDH, serves as the UV down-shifting material. [ 15 ] The absorption and emission spectra for the EuDH dissolved in methylene dichloride (CH 2 Cl 2 ) appear in Figure 1 a. The EuDH absorbs photons with wavelengths from 250 nm to 360 nm and emits at ∼610 nm. Thermogravimetric analysis (TG) and differential scanning calorimetric (DSC) results in Figure 1 b indicate ...