Desenvolvimento de biosubstratos transparentes para a aplicação em diodos orgânicos emissores de luz flexíveis.

Abstract

Biopolymers obtained from onion pulp (Allium cepa L.) and gelana and cashew gums were employed to produce biosubstrates for flexible organic light-emitting diodes (FOLEDs). Onion and gellan substrates exhibited an average optical transparency of 77% and 80%, respectively, in the wavelength range from 600 to 1000 nm, considered as the therapeutic window for Photodynamic Therapy applications. Indium tin oxide (ITO) and 𝑆𝑖𝑂2 thin films were deposited by rf-magnetron sputtering onto these bio-substrates to obtain flexible, transparent and conductive anodes on top of which FOLEDs were produced. ITO films were optimized by varying rf-power during deposition onto the biopolymers and their electrical properties are comparable to the ones of ITO grown on top of glass substrates. The resistivity of this ITO films deposited onto onion and gelana gum substrates were 2.23 × 10-4 Ωcm and 2.80 × 10-4 Ωcm, respectively. The FOLEDs were fabricated using CuPc, β-NPB and Alq3 as organic layers. The onion FOLED exhibited a maximum luminance of about 2062 cd/m2 and maximum current efficiency of 2.1 cd/A. On another hand, the gelana FOLED showed a maximum luminance of about 2327 cd/m2 and maximum current efficiency of 2.9 cd/A. In addition, it has been shown by a flexibility test that FOLEDs work well even when folded over a 1.5 mm radius cylinder. The obtained results suggest the possibility to use these flexible biosubstrates for applications in the field of "Organic Bioelectronics", such as Photodynamic Therapy.