Short description
(English)
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We propose a novel lighting source that uses organic small molecular semiconductors as the active materials within thin film light-emitting diodes. Using the pre-existing deposition capabilities within ETH Zurich that allow organic electronic materials to be deposited in ultra-high vacuum, we will produce multilayer thin films that satisfy the requirements for broad wavelength light emission. A thorough evaluation of the completed devices from a fundamental physical level will enable us to highlight challenges in terms of both materials choice and device design. We will optimise the efficiency of such devices using a variety of methods to optimise both the charge injection and electroluminescent intensity of the devices.
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Partners and International Organizations
(English)
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AT, BE, BG, HR, CZ, FI, FR, DE, EL, HU, IT, LV, LT, NL, PT, RO, ES, SE, CH, UK
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Abstract
(English)
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Organic electronic materials show promise as white-light emitting sources, but currently there are few available technologies that meet the demands of high efficiency, broad-wavelength emission at low cost. Our research program has revealed a highly promising solution, namely utilizing the unusual photophysical properties of aggregated small molecules that emit via the process of singlet excimer emission. We investigated the well-characterized small molecule N,N'-di-1-naphthalenyl-N,N'-diphenyl-[1,1'-Biphenyl]-4,4'-diamine (NPB). The emission of this molecule is normally deep blue (437 nm, FWHM 54 nm) but we are able to induce a broad green luminescence (503 nm, FWHM 112 nm) of comparable intensity to the blue luminescence by reducing the deposition rate to less than 1 nm / min. Further measurements elucidated that the singlet excimer states are responsible for the green emission. We successfully fabricated broad green organic light-emitting diodes that emit via this process. The CIE coordinates of such diodes are (0.26,0.45) but one may tune the emission closer to the white (0.33,0.33) by varying the ratio of the blue to green emitters. Our research highlights that singlet excimer emission has potential impact for solid-state lighting sources, and may be achieved using small molecular thin films.
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