Italian Scientists Build Large-Surface, 12.6% Efficiency Nickel-Oxide-Based Perovskite Solar Modules – pv magazine International

September 24, 2024 Emiliano Bellini

Scientists from the University of Rome Tor Vergata in Italy have developed 15 cm x 15 cm inverted perovskite solar modules based on a hole-transport layer (HTL) made of inorganic nickel oxide (NiOx).

“Our research stands out for optimizing the deposition of nickel oxide over a large area using a blade coater, a scalable technique that is essential to reduce the technology gap between basic research and commercialization,” said lead author Luigi Angelo Castriotta pv magazine“The technique is optimized to perform under standard ambient conditions with an average humidity of 25%, eliminating the need for controlled environments such as nitrogen that are often used in traditional manufacturing methods.”

In inverted perovskite cells and modules, the perovskite cell material is deposited on the HTL and then coated with an electron transport layer (ETL) – the opposite of the conventional device architecture. Inverted perovskite devices typically exhibit high stability but lag behind conventional devices in terms of conversion efficiency and cell performance.

The researchers explained that inverted perovskite cells commonly use poly(triarylamine) (PTAA)-based HTLs, which they said are known for their high efficiency in printed devices. Their choice of NiOx was due to the improved long-term stability that this material offers, in addition to similar levels of efficiency compared to PTAA. “Unlike PTAA, NiO_X “It is potentially inexpensive due to its inorganic nature, is highly photostable, chemically stable, has excellent optical transmission, and is hydrophilic in nature,” they explained.

However, they warned that the integration of NiO_X HTL under ambient conditions using printable methods results in lower efficiency compared to PTAA-based devices. To solve this problem, they decided to print NiO_X above the cell, without the need to use the spin coating process, using the so-called squeegee, a method commonly used to form films of a precisely defined thickness.

“We performed squeegee grinding of nickel(II) chloride (NiCl₂6 hours₂O) solution on indium tin oxide (ITO) substrates under ambient conditions,” the group explained. “Then, the films were annealed at 300 C to accelerate decomposition and oxidation, using atmospheric oxygen to form NiO_X movie.”

The solar panel was constructed from an ITO, NiO substrate_X HTL, self-assembled monolayer (SAM) made of (2-(3,6-dimethoxy-9H-carbazol-9-yl)ethyl)phosphonic acid (MeO-2PACz), a perovskite absorber, ETL based on buckminsterfullerene (C60), AND bathocuproine (BCP) buffer layer and copper metal (Cu) contact.

The first four layers were applied by squeegee spraying under room conditions, while the remaining layers were bonded by thermal evaporation.

“We found that introducing a SAM layer between the nickel oxide and the perovskite significantly improves the morphology and uniformity of the perovskite film, reducing defects such as pinholes and increasing the stability of the device over time,” Castriotta explained.

Tested under standard lighting conditions, the 110 cm² perovskite panel achieved a power conversion efficiency of 12.6%, a short circuit current density of 19.67 mA/cm2 and a fill factor of 63.49%. The device was able to retain 84% of its initial efficiency after 1,000 hours of thermal stress testing at 85°C in air.

“These results underscore the potential of NiO_X in PSCs and open new possibilities for mass, cost-effective production of perovskite solar modules,” the researchers said. “Future research should focus on further optimizing the fabrication process and investigating the commercial feasibility of these technologies.”

The new approach was presented in the study “Stable and Sustainable Perovskite Solar Modules by Optimizing Nickel Oxide Deposition from a Blade Coating in a 15 cm × 15 cm Area,” published in communication materials.

“Our research not only addresses one of the major hurdles to commercializing perovskite solar cells, namely the scalability of the manufacturing process, but does so in a sustainable manner that eliminates the use of toxic solvents and complex manufacturing environments,” Castriotta said. “The result is a promising technology that could accelerate the industrial-scale implementation of perovskite cells while maintaining high efficiency and long-term stability.”