Ink-jet printed perovskite solar panel reaches record efficiency

Technology News |
By Nick Flaherty

Panasonic has developed a large area inkjet printing process to achieve a record efficiency for a thin film perovskite solar panel at 16.09 percent. Other perovskite cells have hit 21 per cent efficiency.

The panel, developed with Japan’s New Energy and Industrial Technology Development Organization (NEDO). has an aperture area 802 cm2: 30 cm long x 30 cm wide x 2 mm thick and uses a glass substrate with a large-area coating method based on inkjet printing, making it more lightweight than other mono- and polycrystalline panels based on silicon.

The inkjet-based coating method that can cover a large area reduces manufacturing costs of modules. In addition, this large-area, lightweight, and high-conversion efficiency module allows for generating solar power highly efficiently at locations where conventional solar panels were difficult to install, such as façades.Solar cells built with perokvskite materials have a structural advantage as their thickness including a power generation layer is only one-hundredth of that of crystalline silicon solar cells, so that perovskite modules can be lighter in weight than crystalline silicon modules. The lightweight property enables various placing styles such as installing on façades and windows by using transparent conductive electrode, which can lead to the wide-spread adoption of Net Zero Energy Buildings (ZEB). As each layer can be coated onto the substrates directly, they can be produced cheaper, compared to the conventional process technology. 

However efficiency in large panels has been a challenge. By focusing on the inkjet coating method that enables the raw material to be coated precisely and uniformly, Panasonic applied that technology to each layer of the solar cell including perovskite layer on glass substrate and realized high power conversion efficiency for a large-area module. Methylamine has thermal stability issue during the heating process during perovskie module production as it is removed from the perovskite crystal by heat and parts of the crystal are destroyed as a result. By using formamidinium, cesium and rubidium alongside, the methylamine is stabilised, contributing to the high power conversion efficiency.

The thin film inkjet coating method also used different dot patterns on each layer, tuning the concentration of perovskite ink to certain content and by precisely controlling coating amount and speed during the printing process. By optimizing these technologies through coating process in each layer formation, Panasonic succeeded in enhancing crystal growth and improving the uniformity for thickness and crystal layer.

Going forward, NEDO and Panasonic continue to improve perovskite layer materials, aiming to achieve high efficiency comparable to that of crystalline silicon solar cells and establish technologies for practical application in new markets as the cost is predicted to fall to 15 yen/W (14c/W).

These results have been published at IPEROP20 (Asia-Pacific International Conference on Perovskite, Organic Photovoltaics and Optoelectronics).

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