Tailoring angular and spectral behaviour in perovskite optoelectronic devices

Controlling the angular and spectral behaviour of light in optoelectronic devices is crucial for meeting the demands of advanced applications. Advanced technologies such as displays and optical communications require precise management of light emission, particularly in terms of intensity and angular dispersion. Similarly, narrowband photodetectors with fine spectral control are essential for applications like colour imaging and machine vision. However, current solutions often rely on external filters or complex optics, and approaches such as charge collection filtering have led to compromises in performance, colour accuracy, or response time. Resonant structures present an alternative solution and have been explored in materials such as silicon, III-V semiconductors, organic compounds, 2-dimensional materials, and quantum dots, showing great promise for tunability, flexibility, and enhanced performance. When combined with the emerging class of metal halide perovskites—known for their exceptional optical and electronic properties, including bandgap tunability through compositional engineering—resonant structures can offer new possibilities. Perovskites are attractive due to their ease of fabrication via low-cost solution-based techniques and their excellent light absorption and charge-carrier mobility, making them strong candidates for advanced optoelectronics. This thesis explores the angular and spectral characteristics, as well as the electric field behaviour, of perovskite materials in different structures through a combination of simulations and experimental studies. By sandwiching perovskite films between plasmonic metal and photonic crystal layers, this work investigates light-matter interactions and demonstrates significant improvements in photoluminescence. The optimized resonant structure achieves enhanced forward photoluminescence and sharp angular and spectral narrowing compared to unconfined perovskite films. Moreover, the thickness of the perovskite layer is fine-tuned to enable precise spectral control, achieving tunability between 485 nm and 565 nm, illustrating a systematic approach to optimizing light-matter interactions. Building on these findings, the resonant structure is further developed for perovskite light-emitting diodes (LEDs) by incorporating additional device layers to tailor both angular and spectral properties. The resulting LED design delivers narrow forward-directed electroluminescence with an angular full-width half-maximum of 36.6°, significantly improved from isotropic unconfined devices, and a spectral narrowing with a full-width half-maximum of 12.1 nm. The versatility of this design allows it to be tuned for wide angle emission, making it a promising candidate for modular, low-cost, and directional light-emitting devices. The incorporation of resonant structures in perovskite devices extends to photodetectors, demonstrating a highly selective narrowband spectral response. Achieving a peak external quantum efficiency of 80% and responsivity of 0.41 A W-1, the resonant cavity-enhanced photodetector offers fast switching, low noise, broad dynamic range, and stable photocurrent. By adjusting the perovskite layer's thickness, the narrowband response can be tuned across a 100 nm range, particularly between 560 nm and 660 nm, ensuring both efficiency and stability even in regions prone to phase segregation. This work highlights the integration of resonant cavity enhancement in perovskite photodetectors, paving the way for high-performance optical sensing, multispectral imaging, and wavelength-selective photonic devices. Overall, the findings demonstrate the potential of engineered optical resonant modes to significantly tailor the angular and spectral characteristics of perovskite LEDs and photodetectors, advancing their applicability in next-generation technologies.

Level dc:type.qualificationlevel

Doctoral

Grantor dc:publisher.institution

University of Cambridge

Year dc:date.issued

2024

Author dc:creator

• Ooi, Zher Ying

Advisor dc:contributor.advisor

• Stranks, Sam

• perovsktie
• resonant cavity
• LEDs
• photodetectors

Licence

• https://apollo8-f-pro.lib.cam.ac.uk/bitstreams/cabaddc7-1940-4a40-91d9-62b3da4a470f/download
• http://purl.org/NET/rdflicense/allrightsreserved

Language dc:language

eng

DOI dc:identifier.doi

https://doi.org/10.17863/CAM.115209

OAI identifier oai:identifier

oai:www.repository.cam.ac.uk:1810/378989