New solar cell design capable of reducing manufacturing costs and increasing efficiency

An innovative new solar-cell design which has the capability to drive down costs of solar cell manufacture, has been created by scientists at the University of Sheffield and energy technology company Power Roll in the U.K.

In a study published in the journal Energy and Environmental Science, collaborating researchers from the University of Sheffield and Power Roll have demonstrated how a unique architecture based on a surface embossed with micro-grooves could also make solar power more efficient.

The remarkable performance of metal halide perovskites in photovoltaic (PV) devices have resulted in significant interest in their use as a competitive solar technology. At present, the majority of perovskite PV devices are based on a multilayer configuration, in which charges are extracted normal to the plane of the device.

Such an architecture however comes with attendant losses, as light can be absorbed in the charge extracting layers before it reaches the active layer. So-called back-contact devices can solve this problem, by instead using laterally-patterned electrodes that harvest photo-generated charges in an in-plane direction.

Researchers have fabricated back-contact perovskite solar micro-modules using a directional deposition technique to deposit electron and hole-selective contacts onto opposing walls of a series of micron-width grooves that have been embossed into a plastic film. By filling the grooves with a methylammonium lead iodide perovskite, efficient back-contact perovskite photovoltaic devices can be created, which – when series-connected – function as an integrated back-contact micro-module.

Such micro-modules are flexible, paper-thin, lightweight and contain no rare-earth metals. They can also be fabricated using rapid, low-cost roll-to-roll processes, and do not require expensive electrode patterning techniques. The development of such a technology opens significant opportunities for the high-volume, low-cost manufacture of perovskite PV devices.

(a) Schematic illustration of directional evaporation onto a groove substrate creating selective electrodes on opposing groove walls. Consecutive layers can be deposited at different deposition angles to control the filling depth of the groove. (b) Schematic of a coated groove after a non-directional coating of Al2O3 followed by an n-type titanium & C60 electrode on one groove wall and a p-type Ni & NiO electrode on the opposite wall. (c) A focussed ion beam-scanning electron microscope image of a cross-section through a 2 μm wide single groove after the deposition of all evaporated layers. The inset and translucent shading indicates the location of the selectively deposited metal electrodes and charge-transporting layers. (d) An image of a flexible groove substrate after the deposition of all evaporated layers.

Professor David Lidzey, from the Department of Physics and Astronomy at Sheffield, who has led on the collaboration with Power Roll, said:

“There is global interest in using solar cells to generate low carbon, green electricity. The design of the back contacted solar module is both innovative and elegant and can potentially capture more of the available light within the device.’’

Neil Spann, CEO of Power Roll, said:

“We believe that our patented microgroove architecture is a game changer. The market opportunities for our solar PV product are significant, including off-grid solutions, commercial and domestic systems, powering the internet of things, portable power generation and military applications. This technology will deliver significant wider environmental, economic and social benefits.”

Dr Trevor McArdle – Senior Research Scientist of Power Roll commented:

“Over the last 40 years, the majority of solar cells have been based on a conventional flat structure, in which layers of different materials are deposited one upon another to create the solar cell. However, we have developed a radically different architecture to make solar cells using a surface patterned by micro-grooves that individually are a fraction of the width of a human hair.”

Ultra-low cost, flexible and lightweight

The innovative 3D solar architecture is designed to remove many of the manufacturing process steps required by existing PV modules. This opens the potential to deploy manufacturing methods already used in other sectors and when coupled with the low cost of the material and high production throughput, results in solar panels produced at one fifth of the cost of the current market leader and less than one tenth of the equivalent lightweight flexible solar panels using standard technology. This means the cost of electricity produced is significantly cheaper than hydrocarbons and eliminates the need for subsidies.

A Power Roll solar module will weigh only four percent of a conventional solar module of the same power weighing less than 0.5 kg per square meter compared to 12 kg per square meter for existing silicon PV panels. This has hugely exciting implications for less developed and off grid areas of the world where it is simply not viable to transport heavy solar panels.

Other benefits of Power Roll’s solar module design include reduced power losses due to shading or defects; removal of expensive transparent conductive oxides; simple and low-cost electrical interconnections; lower carbon footprint and the ability to tune electrical output to match user requirements.

Scaling up to commercialisation

Professor Lidzey, added:

“The devices we have demonstrated have a promising efficiency, whereby seven percent of sunlight power falling onto a single photovoltaic micro-groove device is directly converted to electrical power, this is already around a third of what the best performing but expensive solar cells produce today, and I expect further rapid improvement.”

Building on the work published in this paper, Power Roll and Sheffield have recently successfully produced working mini-module demonstrators comprising 3,400 grooves arranged in 190 individual solar modules within the space of three square centimetres. Power Roll is now focusing on scaling up the technology ready for commercialisation.

Source: Press Release by  Sheffield University and Power Roll. Photo Credit: © Sheffield University. Flexible back contact perovskite micro-module.