Investigating the stability of perovskite light-emitting diodes

Thesis

Metal halide perovskite semiconductors have recently attracted significant attention as a class of materials with huge potential for a wide array of optoelectronic applications. They have shown great promise as emitters in light-emitting diodes where they demonstrate emission wavelength tunability across the entire visible spectrum, narrow emission spectra and high EQEEL in excess of 20%. Despite this excellent performance they have poor operational stability, resulting in lifetimes of 250 hours in the best case.

In this thesis, I first investigate factors which govern the fabrication of efficient green-emitting perovskite LEDs through the implementation and study of different device structures and passivation strategies for green emitting perovskite LEDs. Following this, I investigate the use of 2D/3D perovskite heterostructures as a strategy for efficient green-emitting perovskite LEDs. I systematically alter composition and examine changes in carrier recombination and device performance. Additionally, I study the effect of different experimental protocols on reproducibility of 2D/3D devices which leads to the development of a novel hole injection layer which affords efficient and highly reproducible devices.

In the final experimental chapter, I study the effect of the composition of 2D/3D perovskite LEDs on stability. I demonstrate that the introduction of the cation phenylethylammonium into the perovskite is highly detrimental to operational stability. This leads to investigations into the drivers behind poor operational stability where I reveal that changes to radiative efficiency and charge injection are the primary factors, which is attributed to increased ionic mobility.

Authors: Warby, J

• DOI: 10.5287/ora-ga7kbv8wk
• Type of award: DPhil
• Level of award: Doctoral
• Awarding institution: University of Oxford
• Language: English
• Keywords: perovskite; LEDs; stability; light emission
• Subjects: Optoelectronics; Light emitting diodes; Condensed matter; Nanostructured materials