New Review : Measuring, controlling and exploiting heterogeneity in optoelectronic nanowires

Interwire and intrawire inhomogeneity

Group PhD students Ruqaiya Al-Abri and Hoyeon Choi have written an invited review article for JPhys Photonics, published today.

Lead author Ruqaiya Al-Abri describes this work:

Among the one-dimensional structures, semiconductor nanowires have attracted great attention; from the growth process to the production of functional devices they have been widely studied. The growth condition of the nanowires can lead to non-uniformity (disorder) in the crystal structure, morphology, and geometry of the nanowire. Consequently, this affects the functionality of individual and/or ensembles of nanowires. However, researchers have benefited from disorder; it has been shown that disorder can enhance the performance of ensemble of nanowires such as in photovoltaic devices. This review article attempts to understand the disorder in these structures, investigates the origin of the inhomogeneity within “interwire” and between “intrawire” nanowires, and outlines different approaches to correlate disorder to functional parameters and hence optimize the performance of the nanowires.

Reference: Measuring, controlling and exploiting heterogeneity in optoelectronic nanowires, Ruqaiya Al-Abri, Hoyeon Choi and Patrick Parkinson, JPhys Photonics, (2021) DOI:10.1088/2515-7647/abe282

EPSRC-funded PhD position now available

A fully funded EPSRC studentship (DTP) will be available in the group for a September 2021 start. This studentship is associated with the “Big-data for nano-electronics” project, and is open to UK-based applicants (EU applicants living in the UK may also be eligible for some support).

The project will develop a framework for producing and analysing high-throughput imaging and spectroscopy data for inhomogeneous nano-electronic devices, and will include both experimental and computational work.

In particular, students with a good first degree or MSc in physics, electronic materials, nanotechnology or photonics are encouraged to apply.

For further details, please contact Patrick. Applications must be made via the University site.

Congratulations to group PhD Stefan Skalsky

A post-viva call

A huge congratulations to group PhD student Stefan Skalsky (co-supervised with Prof. Wendy Flavell) who passed his PhD viva with minor corrections. Even more impresively, he managed to deal with the challenges of a video-cal based viva.

His examiners were Prof. David Mowbray (Sheffield) and Prof. Mark Dickinson (Manchester).

New Paper: Visualizing the role of photoinduced ion migration on photoluminescence in halide perovskite grains​

Group student Hoyeon has had a paper accepted in the RSC Journal of Materials Chemistry C, studying the photo-brightening effect in perovskite grains using correlated optical and chemical mapping. In collaboration with the Flavell group and the NanoSIMS group at Manchester, this study linked luminescence lifetime and emission energies to local changes in oxygen and iodine density close to the surface of methyammonium lead iodide grains; a prototypical next-generation photovoltaic material.

This new study unambiguously links the emission efficiency improvement under illumination – the so-called photo-brightening effect – to light-induced migration of iodine into the bulk of the crystal and an increase in oxygen levels close to the surface of the grains. By mapping the emission efficiency and chemical levels on the sub-micron scale, we find that grain size has a decreasing role with light-soaking.

Reference: “Visualizing the role of photoinduced ion migration on photoluminescence in halide perovskite grains​“, J. Mater. Chem. C (2020), DOI:10.1039/d0tc01441a

Conference Proceedings: Spatially and temporally resolved degradation in antisolvent treated perovskite films

Group PhD student Hoyeon Choi has had a conference proceedings accepted for SPIE Europe 2020. As this conference has been cancelled, his talk is available throught the SPIE Digital Form.

In his work, Hoyeon describes the application of confocal and time-resolved spectral mapping to study and understand photobrightening and degradation processes in a prototypical perovskite material fabricated with and without use of anti-solvent treatment.

The presentation and paper are available online now.

Reference: Spatially and temporally resolved degradation in antisolvent treated perovskite films, Hoyeon Choi, Chun-Ren Ke, Stefan Skalsky, Wendy Flavell, and Patrick Parkinson, Proc. SPIE 11365, Organic Electronics and Photonics: Fundamentals and Devices II, 113650Q

New Paper: Heterostructure and Q-factor engineering for low-threshold and persistent nanowire lasing

Group PhD student Stefan Skalsky’s paper on semiconductor nanowire lasing has just been published in Light: Science and Applications. In this new work, Stefan used his newly developed Interferometric Time-Correlated Single Photon Counting system (i-TCSPC) to measure the coherence length of laser emission from nanowires grown by the Liu group at UCL. These measurements allowed the direct calculation of the nanowire mirror reflectivity.

During this study, Stefan found that it was possible to use indirect bandgap materials as a holding state for carriers before they relax into the emissive wells; this finding both allows multi-nanosecond lasing after a sub-picosecond excitation, and record low lasing thresholds through resonant excitation.

This work was supported by TEM provided by the Sanchez group at Warwick.

Reference: Heterostructure and Q-factor engineering for low-threshold and persistent nanowire lasing, Skalsky et al., Light: Science and Applications, 9, 43 (2020) https://doi.org/10.1038/s41377-020-0279-y

PhD Viva: Arturo

Arturo Alanis (the first PhD student of the group) had a successful PhD viva today. His thesis examiners were Dr Hannah Joyce (Cambridge) and Dr Jessica Boland (Manchester).

Arturo has already secured a postdoctoral position to start in a few weeks; we’ll be sad to see him go, but wish him the best for his future beyond Manchester and the North West! Over the past four years Arturo has built much of the experimental tools and techniques for our work on nanowires and nanowire lasers – as well as dealing with lab moves and teaching.

All the best to Arturo on the next stage of his career!