Development of high efficiency OLEDs for applications in optogenetics

Abstract

In recent years, organic light-emitting diode (OLED)s have attracted attention as novel light sources in the biomedical field. However, there are still only few applications in optogenetics, especially at the cellular or neuronal level, due to limitations to the maximum available optical power density and challenges in identifying sufficiently robust encapsulation technology.

In this thesis, we first focus on the development of highly efficient and stable OLEDs. An ultrahigh brightness blue fluorescence OLED is obtained through device structure optimization and selection of suitable functional organic materials. Top-emitting OLEDs are found to degrade substantially when kept at an elevated temperature of 80°C for extended time as is required during device encapsulation via atomic layer deposition (ALD). This problem is solved by studying the underlying mechanism of the electrode / organic interface. Following the investigation of highly efficient emitters and substrates with high thermal conductivity, a vertical AC-driven dual-color top-emitting OLED is fabricated. Integrated devices are explored by combining all requirements for optogenetic stimulation and recording in a single device, i.e. dual color emission, a distributed Bragg reflector (DBR) and thin-film encapsulation (TFE).

The first application of in vitro photostimulation of channelrhodopsin (ChR)-expressing neurons is realized, evaluating the effectiveness of the high-power millimeter-scale blue OLEDs we developed. Next, by inserting an ultrathin buffer at the anode interface, we demonstrate a top-emitting device on a flexible silicon substrate, which may offer the prospect of in vivo neural stimulation with single-cell resolution on a single complementary metal oxide semiconductor (CMOS) chip. Finally, we show how photostimulation and fluorescence imaging of neural activity can be realized simultaneously using a single narrowband dual-color OLED. This integrated device provides the possibility of future implantable light sources in optogenetics.

Date of Award	28 Jun 2021
Original language	English
Awarding Institution	University of St Andrews
Supervisor	Malte Gather (Supervisor)