Flash Infrared Annealing for Perovskite Solar Cell Processing

This protocol is key for using the FIRA method for processing of thin-film perovskite solar cells. The main advantage of this protocol are the quick annealing time, eco-friendliness, and the reproducibility of the thin-film processing. This method has been developed for thin-film perovskite solar cell.

However, it can be expanded for thin-film coating soft and hard materials. To program the annealing cycle, first connect the FIRA oven to a computer and select PID mode. Confirm that table is selected with a time base that is longer than the total duration of the annealing and cooling processes.

After setting the times at which the lamps should be on and off, click START table to run the cycle. To prepare a mesoporous titanium dioxide layer spin-coat 50 microliters of a mesoporous titanium dioxide solution at 4, 000 revolutions per minute for 10 seconds with an acceleration speed of 1200 revolutions per minute then open the gas inlet air valve. Program an annealing cycle of 1200 seconds at 550 degrees Celsius and place the substrates in the FIRA oven.

Start the annealing process under PID mode to yield a 150 to 200 nanometer layer. At the appropriate time point, click STOP table to stop the annealing, then remove the samples when the oven temperature reaches 25 degrees Celsius. To prepare a perovskite layer, first program an annealing step of 1.6 seconds on full power mode, spin-coat 40 microliters of perovskite solution on the substrate at 4, 000 revolutions per minute for 10 seconds and transfer the substrate to the oven.

Then start the annealing process. At the end of the cycle, the substrate surface should turn from yellow to black. Leave the samples in the oven for an additional five seconds for cooling before removal.

Then right-click on the temperature profile to download it as a txt or xlsx file. To evaluate the thin-film, image the substrate on an optical microscope equipped with a xenon light source and infinitely corrected 10X and 50X objectives and simultaneously record the absorbent spectra with an optical fiber integrated into the microscope set up and connected to a spectrometer. Eliminating the antisolvent and reducing the annealing times significantly lowers the energetic and financial costs.

Lifecycle assessment of the perovskite synthesis process shows that FIRA presents only 8%of the environmental impact and 2%of the fabrication cost of the antisolvent method. Additionally, FIRA is compatible with flexible and large area substrates. X-ray diffraction analysis revealed the boundaries of the four distinct perovskite phases observed based on various experimental characterizations.

Another advantage is the data collection and material screening. For example, the temperature profile and x-ray diffraction pattern for a mesoscopic titanium dioxide layer annealed with a FIRA cycle of 10, 15 seconds on, 45 seconds off pulses can be observed. The FIRA oven can reach approximately 500 degrees Celsius allowing the titanium dioxide layer to be centered in just 10 minutes, much shorter than with conventional methods.

Scanning electron microscope imaging of the resulting film shows that the fabricated devices are similar to those made via traditional methods with layers of similar thickness and morphology. FIRA process devices demonstrate an excellent performance, with the champion device showing power conversion efficiencies, fill factors, open circuit voltages, and short circuit photo currents similar to devices fabricated with the antisolvent method, demonstrating that FIRA is a promising alternative processing method for perovskite solar cells. The FIRA method is a powerful technique for perovskite solar cell processing and offer us an unique opportunity for data collection and material screening.