FIRA fabrication process.
FIRA fabrication process.

Solar cells based on the mineral perovskite have made major strides in recent years. Commercialization of this technology is a high priority but there are significant challenges in terms of cost and environmental impact. But scientists believe that a new rapid fabrication method, flash infrared annealing (FIRA) developed by Sandy Sánchez at the University of Fribourg, could hold the key to low-cost environmentally friendly perovskite solar cells.

Along with researchers from Adolphe Merkle Institut University of Fribourg, École Polytechnique Fédérale de Lausanne, Universitat Jaume I, and Technical University of Darmstadt, Sánchez and his colleagues have used FIRA to fabricate planar devices that are more suitable for commercialization and compared them with AS-prepared perovskite.

“Perovskite solar cells represent a new photovoltaic technology with low fabrication cost and high performance,” explains researcher Pablo P. Boix of Universitat de València. “Compared to photovoltaic technologies with similar performance, perovskites offer more versatile systems, such as light weight, semitransparent or flexible applications, and a wide range of fabrication methodologies.”

In the lab, perovskite solar cells are typically fabricated using the so-called antisolvent (AS) method. The process relies on an antisolvent such as chlorobenzene, which is added to a perovskite precursor dissolved in DMF or DMSO. The sudden addition of the antisolvent triggers nucleation of the perovskite, but a long annealing step is required to complete the crystallization. By contrast, FIRA only requires a short IR flash of a few seconds to initiate nucleation and drive crystallization.

“The main drive of our work was assessing the sustainability of the two processing techniques and developing the planar perovskite solar cell devices by FIRA,” explains Boix.

Compared with AS-produced material, FIRA perovskite layers on FTO/TiO2 have much larger crystal domains (40 microns versus 200 nm) but otherwise show similar structural and optical characteristics, with solar cell devices performing with comparable efficiency. Life cycle analysis from “cradle to gate” for the two processes, however, reveals marked differences.

“FIRA is an antisolvent-free process, which results in a more reproducible fabrication method with better up-scaling potential and reduces the amount of toxic solvent required,” points out Boix.

Fabricating planar devices with FIRA cuts the perovskite synthesis time to just 1.2 seconds – significantly faster than AS annealing times of up to an hour. By the team’s calculations, FIRA-produced perovskite solar cells have only 8% of the environmental impact of AS-produced cells and require just 2% of the fabrication costs. FIRA is also compatible with large area deposition techniques such as roll-to-roll processing.

The analysis shows conclusively for the first time, say the researchers, that FIRA can be used to produce planar perovskite solar cells with similar efficiencies to devices produced by conventional methods at a fraction of the cost and environmental impact.

Sánchez et al., Materials Today (2019),