Perovskite solar cells: Thermal stresses are key to long-term stability

Perovskite solar cells are extremely environment friendly and low price in manufacturing. Nevertheless, they nonetheless lack stability over the many years underneath actual climate situations. A global analysis collaboration led by Prof. Antonio Abate has now revealed a perspective on this subject within the journal Nature Opinions Supplies.

The researchers explored the results of a number of thermal cycles on microstructures and interactions between totally different layers of perovskite solar cells. They conclude that thermal stress is the decisive issue within the degradation of metal-halide perovskites. Based mostly on this, they derive probably the most promising methods to enhance the long-term stability of perovskite solar cells.

Perovskites are a large class of supplies with semiconducting properties appropriate for vitality conversion in a solar cell: the perfect of them, the metal-halide perovskites, already ship efficiencies of up to 27%. The manufacturing of such thin-film solar cells requires notably little materials and vitality, so solar vitality might turn out to be significantly cheaper. Nevertheless, when used outdoor, solar modules ought to present an almost secure yield for at the very least 20 to 30 years. And right here, there’s nonetheless a whole lot of room for enchancment in perovskite supplies.

Along with a staff led by Prof. Meng Li, Henan College, China, and different companions in Italy, Spain, UK, Switzerland and Germany, the researchers present that thermal stress is the decisive issue within the degradation of metal-halide perovskites.

Harsh situations in ‘actual life’

“When used outdoor, solar modules are uncovered to the climate and the seasons,” says Abate. Whereas encapsulation can successfully shield the cells from moisture and atmospheric oxygen, they are nonetheless uncovered to fairly massive temperature variations day and night time and all year long. Relying on the geographical situations, temperatures contained in the solar cells can vary from minus 40 levels Celsius to plus 100 levels Celsius (within the desert, for instance).

To simulate this, the perovskite solar cells within the examine had been uncovered to rather more excessive temperature variations in a number of cycles: From minus 150 levels Celsius to plus 150 levels Celsius, and many times. Dr. Guixiang Li (then a postdoc at HZB, now a professor at Southeast College, China) investigated how the microstructure throughout the perovskite layer modified through the cycles and to what extent the interactions with the neighboring layers had been additionally affected by the temperature cycles.

Thermal stress contained in the perovskite movie and in between layers

Collectively, these elements have an effect on the efficiency of the cell. Particularly, the temperature cycles prompted thermal stress, i.e. stress each throughout the perovskite skinny movie and between the totally different adjoining layers: “In a perovskite solar cell, layers of very totally different supplies want to be in good contact; sadly, these supplies usually have fairly totally different thermal behaviors,” explains Abate.

For instance, plastics have a tendency to shrink when heated, whereas inorganic supplies have a tendency to develop. Which means that in every cycle the contact between the layers turns into worse. What’s extra, native section transitions and diffusion of components into adjoining layers have additionally been noticed.

Most promising technique

From this, the analysis groups have derived a method to enhance the long-term stability of perovskite solar cells. “Thermal stress is the key,” says Abate. The principle factor, due to this fact, is to make the perovskite buildings and the adjoining layers extra secure in opposition to thermal stress, for instance by growing the crystalline high quality, but in addition by utilizing appropriate buffer layers.

The scientists spotlight the significance of uniform take a look at protocols for evaluating stability underneath temperature biking and suggest an method to facilitate comparability between totally different research.