A new method for creating thinner and cheaper solar cells

Researchers at the ARC Centre of Excellence in Exciton Science have discovered a new way to fabricate thinner, cheaper, and more efficient solar cells.

The technique is a low-cost, scalable fabrication method called microsphere lithography, developed in collaboration with colleagues at Australia’s National Research Agency CSIRO and the Melbourne Centre for Nanofabrication.

Perovskites are a rapidly emerging class of materials that are revolutionising the world of solar cells. They contain cheap and abundant materials, and can be made through fast and low-cost printing methods. However, most perovskite solar cells to date have used a “sandwich” structure, where the photoabsorber is placed between other active layers. While this has delivered good performance to date, such an approach limits the full potential of these solar cells, as the top layer will reflect or absorb some incoming light.

To overcome this, researchers at the Centre, working with colleagues at CSIRO, pioneered the development of an alternative perovskite solar cell architecture where both charge extracting electrodes are placed under the perovskite, allowing incident light to directly illuminate the photoabsorber surface. Until recently, the team and many researchers around the world have produced the electrode arrays using photolithography, a technique commonly used in the microprocessor industry. Unfortunately, this process requires clean room facilities, making it expensive and slow, and is not viewed as a suitable method for commercial production.

A new article now available in Nano Energy describes a novel method of fabricating perovskite solar cells with a unique back-contact electrode. Here, tiny polystyrene beads are added to a container filled with water. The beads naturally assemble on top of the water’s surface and form a floating compact layer with the thickness of one single bead. This layer can then be transferred onto the solar cell substrate and then subsequently used as an inexpensive mask to produce the required electrode arrays needed to conduct electricity.

The Centre’s researchers have shown that by using their new method, they can not only double the power conversion efficiency of back-contact perovskite solar cells from 4.4% to 8.6%, but also significantly reduce the costs of creating these cells.

PhD Candidate and lead author Siqi Deng from the Centre’s Monash University node said: "This work marks a milestone in progress towards high-efficiency back-contact perovskite solar cells by demonstrating that these devices can be fabricated using photolithography-free techniques at low-cost and high scalability,"

"In contrast with photolithography, microsphere lithography not only delivers improved device performance, but it also significantly lowers the hurdles for fabricating and researching back-contact perovskite solar cells," he said.

It is hoped that more research attention will now be drawn to back-contact perovskite PV devices, and this fabrication technique will accelerate research progress towards higher device efficiency, larger device areas and better device longevity for perovskite solar cells.

“Eventually, when the technology is mature enough, it could go onto people's rooftops,” Siqi said.