Novel Fast Color-Converter for Visible Light Communication Using a Blend of Conjugated Polymers

Abstract

Visible Light Communications (VLC) is a promising new technology which could offer higher data transmission rates than existing broadband RF/microwave wireless technologies. In this paper, we show that a blend of semiconducting polymers can be used to make a broadband, balanced color converter with a very high modulation bandwidth to replace commercial phosphors in hybrid LEDs for visible light communications. The resulting color converter exploits partial Forster energy transfer in a blend of the highly fluorescent green emitter BBEHP-PPV and orange-red emitting MEH-PPV. We quantify the efficiency of the photoinduced energy transfer from BBEHP-PPV to MEH-PPV, and demonstrate modulation bandwidths (electrical-electrical) of ∼200 MHz, which are 40 times higher than commercially available phosphor LEDs. Furthermore, the VLC data rate achieved with this blend using On−Off Keying (OOK) is many times (∼35) higher than that measured with a commercially available phosphor color converter.

Polymer colour converter with very high modulation bandwidth for visible light communications

“…2 Organic colour converters [3][4][5] have the potential to overcome this limit, as they have a shorter emission lifetime (in the order of nanoseconds), and consequently higher communication bandwidths can be obtained. [6][7][8] Semiconducting polymers are low cost, solution-processable materials that can be integrated on a wide range of substrates. They can have high photoluminescence quantum yields (PLQY) and broadband emission that can be tuned by changing the molecular structure, both of which, along with short lifetime, are required in colour converters for VLC.…”

“…BODIPY cored materials (in solution) have been used to extend VLC conversion wavelengths to the red, as optical transmitters with 39 MHz bandwidth and data rates (with simple on-off keying) of 98 Mbit per s. 8 To produce a material with a short lifetime and improved colour rendering, a solid blend of two organic materials was made using the green emitter, poly[2,5-bis(2 0 ,5 0 -bis(2 00 -ethylhexyloxy)phenyl)-p-phenylenevinylene] (BBEHP-PPV) and the red emitter, poly[2-methoxy-5-(2 0ethyl-hexyloxy)-p-phenylene-vinylene] (MEH-PPV). 7 The blend gave a broad emission spectrum with modulation bandwidth of 200 MHz, which had a high CRI value of 76 when mixed with blue LED light, but was limited in efficiency by the 17% PLQY of MEH-PPV. A key materials challenge for high performance VLC sources is therefore to develop new orange-red emitters that can combine fast modulation with high PLQY.…”

Visible light communication using InGaN optical sources with AlInGaP nanomembrane down-converters

“…However, phosphors respond slowly to modulated light, which is not ideal for VLC. Other color-converting materials are therefore being researched for VLC including organic semiconductors [6,7], colloidal nanocrystals [8] and inorganic semiconductor epilayers [9]. The latter offers an all-inorganic, photostable solution to color-conversion, which is particularly attractive for high power applications.…”

Organic semiconductors for visible light communications

“…The transition from T 1 to ground state (known as phosphorescence) has low probability, resulting in a much slower decay time (10 −3 -10 2 s). (c) A comparison plot of the time response for various colour converter materials: a commercial YAG yellow phosphor (CL-827), a CdSe quantum dot, a custom-synthesized BODIPY molecule with oligofluorene arms (Y-BODIPY) [35], the commercial fluorescent polymer 'super yellow' (SY) and two custom-synthesized fluorescent polymers (BBEHP-PPV [34] and BBEHBO-PPV [38]). (d) Chemical structure of the various materials presented in (c).…”