(1991 - Nature) "A low-cost, high-efficiency solar cell based on dye-sensitized colloidal TiO2 films"

.... 20 years later. A 2011 review: "Although much more is now known about the physical and chemical processes taking place during operation of the DSC [dye-sensitised solar cell], the exponential increase in research effort during this period has not been matched by large increases in efficiency."

(2012 - Science) "Efficient Hybrid Solar Cells Based on Meso-Superstructured Organometal Halide Perovskites"

(2012 - Nature) "All-solid-state dye-sensitized solar cells with high efficiency"

(2013 - Nature) "Sequential deposition as a route to high-performance perovskite-sensitized solar cells"

(2013 - Nature) "Efficient planar heterojunction perovskite solar cells by vapour deposition"

There has been a rapid year of progress in the area of dye-sensitised solar cells. Many review papers have been appearing that are out of date before page numbers are assigned. The magic word is perovskite (referring to the crystal structure), whether it be inorganic (CsSnI3) or hybrid organic-inorganic (CH3NH3PbI3). These materials absorb a lot of sunlight and can produce voltages approaching the band gaps of the material. Very impressive!

One of the most interesting developments has been the transition from a mesoporous scaffold of TiO2 to a scaffold of Al2O3 to no scaffold at all. It is clear that the technology is converging away from the original dye-cell architecture towards traditional thin-film solar cells. Many key issues remain, including:

• Pb-free absorber materials.
• Replace Spiro-OMeTAD as the p-type layer (for the sake of atomistic modelling at least).
• Make efficient cells with active areas >> 0.2 cm2*.
• Explain how they work: Electric fields? (Yes), Free carriers? (Yes), Excitons? (No), Ion diffusion? (Yes)

We have been modelling these systems since 2012 thanks to the EU DESTINY network. Our contributions [updated]:

• 2013: Dielectric properties
• 2014: Relativistic band structure; Molecular ferroelectricity; Dipole domains
• 2015: Band alignments; Polyanions; Defect chemistry; Chemical bonding; Neutron scattering; Ion transport; Microstructure; Phonons

There are no easy answers; standard perovskites are notoriously difficult to model, hybrid perovskites are a nightmare. It is always nice to be challenged! To keep track of the field, I have started a hybrid perovskite paper collection.

*There is something uncomfortable about efficiencies reported with an active area as small as 0.075 cm2. Plenty of room for noise & artifacts, and not in the spirit of a practical solar cell.

"Phonopy is an open source package of phonon calculations based on the supercell approach." It is a wonderful lattice dynamics package, developed by Prof. Atsushi Togo, which links to a wide variety of electronic structure packages. Since it is only used for pre- and post-processing of phonons, it is light enough to run on your laptop.

There is an official Mac installation guide on the website, but I am not a big fan of MacPorts. Each step is simple, but there are many of them. I had help along the way from Adam Jackson. The basic starting point is having XCode with command-line tools (note in OS 10.9, this requires you to run xcode-select --install after installation).

1. Feed your Python with Scipy Superpack
- A script to install the latest versions of NumPy (linear algebra), SciPy (numerical algorithms), Matplotlib (plotting), iPython (interactive shell for python).
chmod +x install_superpack.sh
./install_superpack.sh

2. Pip your Python
- Two more dependencies (and yet another package manager):
sudo easy_install pip
sudo pip install lxml
sudo pip install pyyaml

3. C hack
- Depending on your version of XCode, the default C compiler might be Clang (which fails for Phonopy with "'omp.h' file not found"). Change it back to gcc by using export CC=gcc.

4. Nearly there...
- You can now download Phonopy. Enter the main directory and run
python setup.py install --home=.
and you will need to add its path to .bash_profile:
export PYTHONPATH=/Volumes/Unix/progs/phonopy/phonopy-1.7.1/lib/python

5. Happy phonons
Once the phonopy bin is in your path, simply type phonopy

aron$ phonopy</p>

_ __ | |__   ___  _ __   ___   _ __  _   _
| '_ \| '_ \ / _ \| '_ \ / _ \ | '_ \| | | |
| |_) | | | | (_) | | | | (_) || |_) | |_| |
| .__/|_| |_|\___/|_| |_|\___(_) .__/ \__, |
|_|                            |_|    |___/

I  just spent a wonderful weekend at my Aunt's house in Cork (I really recommend her guest house). As well eating the exceptional food in West Cork, one of my favorite ways to spend time is at the Time Traveller's Bookshop. On my last visit I picked up an early collection of papers on wave mechanics, and this time I bought the transcript of a lecture by Max Born delivered to the Durham Physical Society in 1943.

"Experiment and Theory in Physics" is a nice essay on the scientific process in the context of the birth of quantum mechanics in the early 20th century. Examples of inductive and deductive developments are given, but he really emphasises how the rapid progress at the time was driven by the abundance of reliable experimental data and a handful of very intuitive scientists.

He concludes the lecture with: "My advice to those who wish to learn the art of scientific prophecy is not to rely on abstract reason, but to decipher the secret language of Nature from Nature's documents, the facts of experience". Strong words from a theoretical physicist.

Last year I wrote about my on-going research collaborations in South Korea. I have been fortunate enough to return this year, funded through the Office of Internationalisation at my University. I have just posted a guest blog on the formal delegation activities.

My sincere thanks (again) to the Materials Theory Group of Aloysius Soon. Last week, they treated myself and Adam Jackson incredibly well. We held our first joint research workshop (MICE), which will be followed up in September when four of their group travel to the UK. We also visited KAIST and SNU. Back to the real world now, with a group meeting at 9:15 am this morning!

(Welcome to Yonsei)

(소녀시대)

(Seoul City Hall)

I can't really provide an objective criticism of "The Fall of the Faculty: The Rise of the All-Administrative University and Why It Matters", since I was already sold on the title. In truth I purchased the book to reinforce and qualify my experiences of university bloat and bureaucracy.

Benjamin Ginsberg, a political science professor at John Hopkins, writes very well. This could easily have been a rambling vent of hot air, but it is in fact a coherent, well researched and lighthearted book. Many of the anecdotes are so depressing that you just have to laugh. While it is North America-centric, the devolution appears to be universal.

The central causes of concern are the rapid decrease in the faculty to administrator ratio, the general increase in bureaucracy (and "deanlets"), and the shift of priorities away from core research and teaching in universities. We hear of presidents using research grant overheads to purchase antique commodes, a proliferation of retreats and networking events to no particular end, and the research office's primary role as university tax collectors. My personal experiences (at various institutes) of the complication of simple tasks and administrative incompetence are trivial in comparison.

The book ends with a chapter on what can be done to remedy the situation. There are few answers and a largely defeatist tone: "But if resistance is futile, it remains essential". I am happy to join the resistance, and if nothing else I now feel more aware* of what lurks beneath the surface.

*Looking at the current vacancies on my university webpage, one new position consists of: "The Recruitment & Staff Engagement Co-ordinator will support and co-ordinate projects and Human Resources activities to ensure that the department positively engages and develops its team to deliver organisational objectives". At a time when academic staff are struggling to find any funding for PhD students to support their research, this sounds like a frivolous investment. Maybe I am just becoming cynical in my middle age?

Yesterday I received an earnest email from a researcher working in my field asking how I write so many papers. I don't have an ideal answer, but my responses* to their specific questions are given below.

Scientists are a varied bunch of people. I know many excellent theoretical and computational researchers who hate to write. They are content with knowing a result and feel no inclination to share it with the world. The classic Whitesides' paper guide makes the reasons for dissemination clear. However, reluctance to publish is understandable. In many cases, the preparation of a decent manuscript can take longer than the creation and analysis of the original results. Then you may have to deal with judgemental editors and unstable reviewers. Publishing a scientific paper is a stressful endeavour at the best of times!

Back to the e-mail:

1) Do you have your-own-way to design papers?
I would say that I design projects rather than papers. Every day I try to browse new publications in my field, and I like to read many older books. From these I keep a list of interesting projects, with some being specific questions and others being broader subjects. I do the same when I attend conferences, so now I have a healthy database of topics for new students to tackle (and for myself when there is an excess of computer power).

Approaching the writing of a paper, usually one of two things happens: (a) I have a clear result that provides a complete story. This is the easiest type of paper to write: following a rough outline, it can almost be a stream of consciousness (sitting in a quiet room for a day). (b) I have a large set of data that is systematic, but makes no obvious story. This problem is always challenging, and my typical approach is to design figures, which I iteratively modify and rearrange until a coherent outline and narrative emerges (this process often involves additional computations).

2) What will be the key of that efficiency in writing/publishing the papers?
The technical aspects of publishing definitely become more efficient with time, e.g. building up a comprehensive database of references and mastering LaTeX / image generation. I find the creative writing process is limited by the state of mind. I really need quality time to write a paper (turning off my phone, disconnecting from the internet, and a nice cup of tea).

On a higher level, project and time management can be an issue. Learning how to keep track of and prioritise multiple projects is an essential skill.  Personally, I am an Evernote addict.

3) Would you mind explaining me your steps of how you publish papers from your research problems? For instance, I was very impressed when I read your APL paper on indium oxide. One of the reasons is that you made really good story without any unnecessary data. For me, I tend to write a paper after I get sufficient data. Then, when I start writing, I don't know what to say since there are so many things to tell…
This paper came from a side project, which I wasn't funded to investigate at the time. I had published on the surface structure of indium oxide in the past, but one open question remained, related to surface defects. My starting point was a simple electrostatic model (taken from a 1983 paper by Dorothy Duffy), which was actually run on my laptop on a flight to Korea. This gave some exciting insights (in relation to the change in oxygen environment towards the surface). It also provided enough evidence to justify a full electronic structure study (so I wrote a script to loop through all possible combinations on our national supercomputer). In fact I had many more results (e.g. vacancy - vacancy interactions), but I left them out as they didn't add to the central story and would have made the narrative too complicated for Applied Physics Letters. It was at the outline stage when I decided what results would be included, as well as what point each paragraph would try to convey.

4) Other than above questions, do you have any suggestions for me?
I can think of three points that have helped me:
(a) Audience. In our field,  the target audience could be people with a backgrounds in physics, chemistry or materials science/engineering (both theorists and experimentalists). It is challenging but worth the effort to make all work as clear as possible to those who you think will be most interested in the results.
(b) Multitask. I always recommend that my students have at least two on-going projects. If one is producing no results or making little sense, a change can really help. Also do not be afraid to abandon a project altogether (I have had many ideas that just didn't work).
(c) Collaborate. Working with people from different backgrounds is always fruitful in terms of forming new ideas and solutions. I owe a lot to my collaborators, many of whom have now become close personal friends. You could work alone, but it wouldn't be as enjoyable or productive.

*Hopefully I don't come across as too pretentious; I still have a lot to learn too.