Made to Measure… Printed Solar Cells

Who are you? Harry Cronin

What is your role? I’m an EngD Research Engineer at the University of Surrey and DZP Technologies

What is your work about? I’m working on the scale-up of printable solar cells based on organic-inorganic halide Perovskite materials.

I beg your pardon? Perovskite materials have the general formula ABX3. By changing the atoms or molecules which sit at the A, B and X positions these fascinating materials can be designed to have a wide range of optical and electronic properties. Recently, it has become clear that halide Perovskites are an excellent material for making solar cells. These materials use a small organic molecule on the A site, a metal like lead or tin on the B site and a halide such as iodine on the X site. The efficiency with which the best Perovskite devices convert sunlight into electricity has been pushed from 3.8% in 2009 to over 20% today. But the real advantage of Perovskite solar cells is that they are simple to make – simply deposit a precursor solution, and the Perovskite forms on drying. This property makes them ideal for printing, but owing to a number of unsolved challenges a printed Perovskite cell has yet to be commercially demonstrated.

Solar Harry

Figure 1 – The author, grinning inanely, prepares to coat a conductive silver substrate with a second layer using doctor blading.

Why? Solar cells could potentially play a major role in reducing carbon emissions, but are currently too expensive to compete with fossil fuels in many applications. By using cheap, high-throughput printing technologies, similar to those used to produce newspapers, cell prices could potentially be slashed. This is part of a wider trend in electronics manufacturing, in which people are trying to make all sorts of ultra-low cost devices by means of printing. Previous work at DZP Technologies has produced prototype printed cells, and the aim of my project is to improve the efficiency of these prototypes by the introduction of Perovskites. There are many challenges to be overcome with the scale-up of this technology.

And? Printed solar cells consist of multiple layers, each of which must be simultaneously optimised and controlled both in terms of materials and processing. In my research I have looked at a method for increasing the conductivity of several of these layers using high intensity light pulses. Put simply, more highly conductive interlayers will mean better-performing solar cells. In parallel to this I have investigated the behaviour of the Perovskites under different processing conditions, which will be vital knowledge as we work towards scaling up the technology.

So what? If this technology can be taken from the lab to commercial scale, we could start to see solar cells in many new places. As well as being cheaper, printed solar cells open up a range of new applications due to their light weight and mechanical flexibility. For example, flexible solar parking shades could be used to charge electric vehicles parked underneath them. Or, highly portable rolls of solar cells could be developed for camping or use in disaster zones.

Final Thought: Made to measure printed solar cells have the potential to offer a step change in the affordability of solar power, alongside flexibility, low weight and large area. Coming soon to a rooftop near you (we hope)!


Made to Measure…Supercapacitors

Who are you?: Richard Fields
What is your role?: PhD Researcher
What is your work about?: Manufacturing and Characterising Supercapicitors
I beg your pardon?: High(ish) energy and power storage density materials that can release their stored energy quickly (but safely). I’ve been looking at both manufacturing (scaling up) and new materials (composite structure that contained some electrodes with high power density and some with high energy density). The ability to select the ratio during manufacturing means cells can be tailor made to specific applications where a certain ratio of energy to power is required.
OK. Why?: Energy storage is a fundamental requirement for having a truly high tech society, where energy production is decoupled from immediate energy consumption. Therefore, storage is an absolute necessity for utilising clean but intermittent renewable resources; maintaining a resilient power grid and powering a multitude of portable electric devices. At its simplest four aspects need to be considered: energy density, power density, cycle life and cost (Figure 1). Batteries and traditional capacitors are shown to be opposite in their properties, batteries are good at storing lots of energy but are slow to deliver it while capacitors are good at delivering energy rapidly but only store a tiny amount of it. Supercapacitors sit in the middle. They can store a small yet significant amount of energy and have the capability of delivering it fast. The best property is that they can be cycled millions of times with minimal degradation, a battery can only handle thousands of cycles before it must be replaced.


Figure 1: Graph of Energy and Power storage densities, indicating where typical devices sit.
And?: My work looks at increasing the energy density (Wh/kg) and power density (kW/kg) of supercapacitors. This is necessary in order to make supercapacitors more desirable as consumer grade products, currently their energy density is about a quarter of what is required to see widespread adaption.
So what?: An example of good use would be in an electric vehicles, supercapacitors can deal with short but intense activities such as breaking and acceleration while batteries can provide a constant supply during cruise. This would reduce the stress on battery systems and thus increase their usable life.
Final Thought: I hope to see widespread adoption of supercapacitors as part of hybridised systems, the technology could greatly improve the efficiency and lifespan of electrical systems if implemented effectively.