High-density integration of ultrabright OLEDs on a miniaturized needle-shaped CMOS backplane

Sabina Hillebrandt*, Chang-Ki Moon, Adriaan J. Taal, Henry Overhauser, Kenneth L. Shepard, Malte C. Gather*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

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Abstract

Direct deposition of organic light-emitting diodes (OLEDs) on silicon-based complementary metal–oxide–semiconductor (CMOS) chips has enabled self-emissive microdisplays with high resolution and fill-factor. Emerging applications of OLEDs in augmented and virtual reality (AR/VR) displays and in biomedical applications, e.g., as brain implants for cell-specific light delivery in optogenetics, require light intensities orders of magnitude above those found in traditional displays. Further requirements often include a microscopic device footprint, a specific shape and ultrastable passivation, e.g., to ensure biocompatibility and minimal invasiveness of OLED-based implants. In this work, up to 1024 ultrabright, microscopic OLEDs are deposited directly on needle-shaped CMOS chips. Transmission electron microscopy and energy-dispersive X-ray spectroscopy are performed on the foundry-provided aluminum contact pads of the CMOS chips to guide a systematic optimization of the contacts. Plasma treatment and implementation of silver interlayers lead to ohmic contact conditions and thus facilitate direct vacuum deposition of orange- and blue-emitting OLED stacks leading to micrometer-sized pixels on the chips. The electronics in each needle allow each pixel to switch individually. The OLED pixels generate a mean optical power density of 0.25 mW mm−2, corresponding to >40 000 cd m−2, well above the requirement for daylight AR applications and optogenetic single-unit activation in the brain.
Original languageEnglish
Number of pages11
JournalAdvanced Materials
VolumeEarly View
Early online date5 Sept 2023
DOIs
Publication statusE-pub ahead of print - 5 Sept 2023

Keywords

  • OLED
  • Aluminum contact
  • Reactive ion etching
  • Implant
  • Shank
  • Optogenetics

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