Flexible Candlelight Organic LED on Mica

Abstract

Candlelight-style, blue hazard-free light sources have been long desired in order to minimize the threats of blue emission on human health, artifacts, ecosystems, and night skies. Flexible light sources can enable numerous innovative products that are wearable, rollable, foldable, and portable. If also transparent, more applications including smart displays, lighting, signage, etc., can be implemented. However, current flexible lighting sources have issues like the use of environmentally unfriendly materials and poor lifetimes. Here, we show the fabrication and lifetime study of a candlelight-style organic light-emitting diode (LED) on high-flexibility, transparent mica that is 100% plastic-free. We found that the mica substrate coated with a transparent conductor survived a record-high bending curvature, i.e., 1/5 mm–1 and 50,000 bending cycles at a 7.5 mm bending radius. The candlelight organic LED fabricated thereon showed a good lifetime that is 83% of that on glass. The blue light-less emission permits at 100 lx an exposure limit of 47,000 s, while the exposure limit is 320 s for a cold-white counterpart; upon exposure at night for 1.5 h, it suppresses 1.6% melatonin, while 30% melatonin is suppressed for the cold-white counterpart. Our results demonstrate how blue hazard-free lighting sources are fabricated on eco-friendly mica that is highly flexible, and the resultant device showed a lifetime approaching that on glass due to its high resistance against moisture and oxygen penetration. The findings suggest that mica can be a good candidate for flexible transparent devices. We expect that these could bring up opportunities to promote omnifriendly lighting applications with a higher degree of design flexibility.

Permissible viewing times of educational projector and TV

“…To explore if some of the threats can be quantified, a few studies were carried out about the effect of wavelength on photoretinitis [ [8] , [9] , [10] , [11] , [12] , [13] , [14] , [15] , [16] , [17] , [18] , [19] , [20] , [21] , [22] , [23] ]. The threat was quantified via the use of a permissible exposure-limit [ [24] , [25] , [26] , [27] , [28] , [29] , [30] , [31] , [32] , [33] , [34] , [35] , [36] , [37] , [38] ]. For examples, Okuno et al used the permissible exposure-limit to evaluate the blue-light hazard of various light sources [ 24 ].…”

“…Besides the maximum permissible exposure limit (MPE), Jou et al also applied a new index, melatonin suppression sensitivity (MSS), to quantify the threat of light at night on melatonin secretion [ 35 ]. They also applied MPE and MSS to demonstrate a fabricated candlelight-style OLED to be eye- and physiologically-more friendly than the blue enriched counterparts [ [32] , [33] , [34] , [35] , [36] , [37] ]. Furthermore, Jou et al reported an easy-to-apply formula and a ready-to-use table derived therefrom to enable a quick determination of the maximum permissible exposure limit (MPE) of any given desk lamp by knowing its labelled color temperature and luminous flux [ 38 ].…”