Tunable Near UV Microcavity OLED Arrays: Characterization and Analytical Applications

Abstract

A new approach is demonstrated to fabricate narrow‐band emission near‐UV microcavity OLEDs (μcOLEDs) with peak emission at ≈385 nm, in near‐perfect alignment with the narrow primary 385 nm absorption band of Pt octaethylporphyrin dye, using 4,4′‐bis(9‐carbazolyl)‐1,1′‐biphenyl (CBP) as the emissive layer. Although OLEDs have been extensively operated at optical wavelengths, only few have achieved near‐UV emission. Yet there is a growing need for portable compact narrow‐band near UV sources for many biomedical and forensic applications. A microcavity effect, due to metallic electrodes enclosing an optical cavity, is employed to achieve the desired narrow peak emission. An Al/Pd bi‐layer anode enables attaining a turn on voltage of 3.8 V and a 4,4′‐cyclohexylidenebis [N,N‐bis (4‐methylphenyl) benzenamine] (TAPC) layer improves electron‐hole recombination in the emissive layer. The fabricated μcOLED is efficiently used as the excitation source in a structurally integrated all‐organic oxygen sensor. Moreover, a CBP‐based combinatorial array of μcOLED pixels is fabricated by varying the thickness of the organic layers to obtain nine sharp, discrete emission peaks from 370 to 430 nm, employed in an all‐organic on‐chip spectrophotometer. The photodetectors are based on P3HT:PCBM (poly(3‐hexylthiophene):[6,6]‐phenyl‐C60‐butyric acid methyl ester) or the more sensitive PTB7:PCBM (PTB7 is polythieno [3,4‐b]‐thiophene‐co‐benzodithiophene). Simulations of the OLEDs' emission are used for analysis of the experimental data, assisting in device fabrication.

Exploiting the Potential of OLED-Based Photo-Organic Sensors for Biotechnological Applications

“…This replacement increased sensitivity by a factor of 1.9. The all-organic oxygen sensor has been further refined by using a near-UV µC-OLED equipped with an Al/Pd bi-layer anode and a 4,4`-bis(9-carbazolyl)-1,1`-biphenyl emissive layer (peak emission ≈ 385 nm) [38]. In contrast to the green µC-OLED, the µC-near UV-OLED exhibited linear-SV dependence over the entire tested range of oxygen concentration.…”

Organic Solar Cells: Degradation Processes and Approaches to Enhance Performance

“…They can be easily integrated with organic light emitting diodes (OLEDs) for analytical applications [62]. The absorption spectra can be tuned and charge transport properties can be improved by synthesis of new materials.…”

Organic Photodetectors in Analytical Applications

“…Using both CuPc/C70 and P3HT:PCBM OPDs (Figure 5a), a dual sensing platform for dissolved O2 (DO) and pH monitoring was demonstrated using green and blue μcOLEDs, respectively. Extending the previous work, Manna et al [77] replaced the green μcOLED with a near UV μcOLED as the excitation source for an all-organic oxygen sensor. Since the oxygen sensitive dyes PtOEP and PdOEP have a stronger absorption in the near UV, the use of the near UV device significantly enhanced the SNR.…”

“…To demonstrate the potential of these tunable μcOLED arrays for on-chip applications, 12 different colored pixels on a 2″ × 2″ glass were used as the light source and the absorption of a spin-coated P3HT film on glass was measured initially using a PMT PD. In a subsequent extension of this work, a near UV 4,4′-bis(9-carbazolyl)-1,1′-biphenyl (CBP)-based combinatorial array of μcOLED pixels was fabricated by varying the thickness of the organic layers to obtain nine sharp, discrete emission peaks from 370 to 430 nm [77]. This array was employed in an all-organic on-chip spectrometer [77].…”

“…In a subsequent extension of this work, a near UV 4,4′-bis(9-carbazolyl)-1,1′-biphenyl (CBP)-based combinatorial array of μcOLED pixels was fabricated by varying the thickness of the organic layers to obtain nine sharp, discrete emission peaks from 370 to 430 nm [77]. This array was employed in an all-organic on-chip spectrometer [77]. Figure 11a shows the schematics of the spectrometer and Figure 11b shows the absorption spectrum of an Alexa fluor 405 film, a dye extensively used in biological fluorescence imaging, obtained with the spectrometer.…”