L R AS Published on Monday 11 May 2020 - n° 321 - Categories:cells

Creating new test procedures for perovskite cells and tandems

The advent of perovskite and tandem cells is forcing laboratories and test machine manufacturers to change the procedures currently used in silicon cell production cycles. In the laboratory, there is time to measure

performance over a period of several minutes to be sure of its characteristics. The closer the technology gets to mass production, the more you need to know the characteristics of the production in a few moments. This forces suppliers of flash test equipment to develop new processes. New technologies will be required for the measurements and the new standards on which these measurements will be based.

A new approach to online testing will be required, as there are fundamental differences in the characteristics of perovskite material, including how it reacts to testing and how it will meet certain certifications.

For example, perovskite cells have a maximum power point. It takes some time for it to stabilize, and wait before taking action. In addition, the efficiency will be slightly different when scanning from low to high voltage or vice versa. Perovskite cells and tandems should be measured with different scanning speeds and scanning directions over a period of several minutes.

The light spectrum is another key consideration. In tandem cells, the current flowing through both cells must be identical. If there is not a perfect spectral match between two tandem cells, one cell may limit the other. It is also useful to adjust the spectrum to see which cell actually limits the other. This is done by adding more blue or more red to see whether it is the upper or lower cell that is limiting the efficiency. These notes will also be useful during production.

Mass production does not leave much time for measurements. However, the nominal power is fundamental for the developer who calculates the cost price of the electricity. He needs the lowest possible uncertainty. This refers to perovskite cells, whose performance must be measured precisely in high-speed production in order to be competitive. Manufacturers hope to be able to flash their cells every second. For the time being, equipment suppliers have not yet found definitive solutions. Before taking measurements, the cell must already be accustomed to light and a temperature of 25°. The constraints are high.

The production will have to be at a high rate and homogeneous. The production batches should be similar, which should make it possible to compare the flash measurement with that of the stabilised measurement. The production will be adapted according to the comparison according to the flash, time, intensity.

The equipment manufacturers are beginning to seriously study the question. The solution has not yet been found. Will it be found before the start of mass production? Oxford PV claims to have a solution planned for in-line testing of its tandem cells. The company claims to know some equipment suppliers. This solution would consist of flashing the silicon cells at the end of their production, and then the complete cell when the perovskite cell is assembled. The aim is to ensure that the product actually meets the requirements.

PV Magazine of 2 May

Subscribe to the newsletter "Le Fil de l'Actu"...

Most read articles in the last 10 days