New method for making perovskite solar cells at scale

Australian researchers have discovered that a key component of next-generation solar panels can be created without expensive, high-temperature fabrication methods, demonstrating a pathway to large-scale, low-cost manufacturing for commercial applications.

Nickel oxide (NiO) is used as an inexpensive hole-transport layer in perovskite solar cells because of its favourable optical properties and long-term stability. Making high-quality NiO films for solar cells usually requires an energy-intensive and high-temperature treatment process called thermal annealing, which is not only costly but is also incompatible with plastic substrates. This precluded the use of NiO in the proposed manufacture of printed photovoltaics at commercial scale.

Now researchers at the ARC Centre of Excellence in Exciton Science, based at Monash University, have identified a way to create NiO films of sufficient quality in solution and at relatively low temperatures of less than 150°C. Their method has been published in the journal Solar RRL.

The researchers, in collaboration with their colleagues at CSIRO, used 4-hydroxybenzoic acid (HBA) or trimethyloxonium tetrafluoroborate (Me₃OBF₄) ligand-modified NiO nanoparticles and a microfluidic mixer, which promotes high-pressure mixing of low volume liquids, to distribute the nanoparticles evenly prior to depositing them on the substrate. The chemical process, developed in collaboration with the Australian National Fabrication Facility, could contribute to the scalable fabrication of inorganic and inexpensive, high-performance films able to be used in the commercial production of flexible solar panels.

The researchers have recorded power-conversion efficiencies of 17.9% and 17.5% respectively in prototype devices, compared to 16% for a previous comparable approach, which lacked the advantages of the ligand exchange and also required a post-processing oxygen-plasma treatment step. Significantly, the new devices exhibited just a 0.2% reduction in efficiency over an intensive 300-hour testing period, providing a strong indication of their potential suitability for commercial applications.

“Our work showcases that high-temperature processing of functional materials for solar cells can be omitted using facile processing ways,” said Monash’s Monika Michalska, joint lead author of the study. “It is a crucial step for commercialisation of perovskite technology.”

Image credit: ©stock.adobe.com/au/mvtstockshot

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