Organic Visible Light Communications: Recent Progress Invited Paper Paul Anthony Haigh 1,2 , Zabih Ghassemlooy 1 , Francesco Bausi 3,4 , Ioannis Papakonstantinou 2,4 , Hoa Le Minh 1 , Sandro Francesco Tedde 5 , Oliver Hayden 5 and Franco Cacialli 3,4 1 Optical Communications Research Group, Northumbria University, Newcastle-upon-Tyne, NE1 8ST, UK 2 Department of Electrical & Electronic Engineering, University College London, London, WC1E 6BT, UK 3 Department of Physics and Astronomy, University College London, WC1E 6BT, UK 4 London Centre for Nanotechnology, University College London, WC1H 0AH, UK 5 Corporate Technology, Siemens AG, Erlangen, Germany e-mail: paul.anthony.haigh@ieee.org; z.ghassemlooy@northumbria.ac.uk; sandro.tedde@siemens.com; f.cacialli@ucl.ac.uk ABSTRACT The field of organic visible light communications is rapidly gaining interest in the research community as a standalone technology in optical wireless communications. Organic small molecule and polymer photonic devices are the focus of wide ranging research due to fascinating characteristics such as mechanical flexibility and extremely low cost solution based processing. On the other hand, charge transport mobility in organic semiconductors is orders of magnitude lower than in inorganics, resulting in corresponding bandwidth limitations and generating a major challenge for increasing transmission speeds. Recently, however, data rates have been demonstrated at Ethernet speeds (10 Mb/s) for the first time. In order to reach such transmission speeds we reported several substantial steps of progress in the literature which will be reviewed in this work. Keywords: Equalizers, organic LEDs, organic photodetectors, polymer-LEDs, visible light communications. 1. INTRODUCTION Modern wireless local area networks have made it possible to stream high speed information to users’ smart phones and laptops wirelessly from the internet. There is an alternate implementation of the same concept based on data communications via illumination of visible light emitting diodes (LEDs), a concept better known as visible light communication (VLC). The field of visible light communications (VLC) falls under the latter category and has been widely proposed over the last decade as a solution to the so-called “last-meter” bottleneck resulting from the exponentially increasing demand for data. VLC is envisaged as an alternative to radio frequency (RF) based communication technologies due to over-allocated and therefore expensive spectrum availability. VLC offers advantages such as inherent security, license free operation and dual solid state lighting and data communications functionality - a unique feature that does not exist in any other rival technologies. Ever since the discovery of electroluminescence in polymers [1] a growing amount of research activities have gone into improving the power efficiency, light output [2, 3] and lifespan [4, 5] of polymers in diode based device structures. Organic small molecule and polymer light-emitting diodes (SMOLEDs and PLEDs, respectively) have been gaining interest in recent years due to several promising characteristics such as ( i) large photoactive area panels, (ii) flexible substrates and (iii) low cost solution based processing, to name three. In addition organic LEDS are environmentally-friendly and could be significantly more efficient than conventional lighting and unlike fluorescent tubing they do not contain any toxic mercury. As a result of these particular features, organic LEDs have been the focus of research in the areas of solid state lighting [6], display technology [7] and optical wireless broadcasting networks [8-11]. To the best of our knowledge, the first research work on combining organic photonic devices with optical communications was reported in [12], which proposed ~2.8 Mb/s transmission of audio signals over a plastic fibre. In [13] a review of the potential for using organic devices in communications systems was reported that made several key observations including a discussion of the status of organic optical communications in comparison to more traditional inorganics. The conclusion was that organics devices must complement inorganics devices because they have contrasting advantages and disadvantages; firstly inorganic optical systems are well established in long haul high capacity backbone networks and are well supported by industry and infrastructure. Secondly, organics devices are ideally suitable for applications where inorganics can’t be used; i.e. those requiring varying wavelengths, large photoactive areas and mechanical flexibility such as mobile device screens. Finally the advantages of both technologies can be combined, one such example is short reach interconnects where low cost polymer fibres with inorganic photonic components can provide high capacity cost effective connectively over short distances (~50 m) [14]. 2. VLC LINKS UNDER TEST AND RESULTS It was not until our work in [15] that organics were considered in the context of VLC links where we experimentally demonstrated a 550 kb/s link that utilized a SMOLED and a silicon PIN photodiode (PD) as the transmitter and receiver, respectively. In our latest works we have reported transmission speeds of 10 Mb/s using