| Work Detail |
German researchers claim to have reduced ribbing effects when using slotted die coating for the production of perovskite solar cells. The results are reportedly the most efficient solar cell built using this technique to date.
Scientists at the Helmholtz-Zentrum Berlin für Materialien und Energie GmbH in Germany have developed a new precursor ink technique to improve film quality in perovskite halide solar cells. In the study “ Ink Design Enabling Slot-Die Coated Perovskite Solar Cells with >22% Power Conversion Efficiency, Micro-Modules, and 1 Year of Outdoor Performance Evaluation” (Ink design enabling slot-coated perovskite solar cells with greater than 22% power conversion efficiency, micromodules, and one year of outdoor performance evaluation), recently published in Advanced Energy Materials, the researchers explain that they used a formamidinium lead triiodide (FAPbI3) precursor ink based on 2-methoxyethanol in the slot-die coating process.
Slot-die is a coating process used to deposit thin, uniform films with limited material waste and low operating costs.
“Slot die coating is one of the most promising processes enabling sheet-to-sheet coating, continuous roll-to-roll coating, and solution processable optoelectronic device technology such as organic electronic devices and polymer solar cells. the team stated, noting that spin coating is routinely used by industry for perovskite cell production.
The researchers noted that the new precursor-ink method is intended to avoid so-called ribbing effects that often occur in slot-die perovskite solar devices and cause irregular shapes in deposited wet perovskite films.
Ribbing is a common effect seen in the downstream meniscus when the viscous and capillary forces between the ink, the slot-die, and the substrate are unbalanced."
They adjusted the viscosity of the ink using acetonitrile (ACN) with a concentration of 46%. The compound acted as a cosolvent for the FAPbI3 thin film and improved its quality and the homogeneity of the layer.
The German group used this technique on a small-area solar cell, which achieved a power conversion efficiency of 22.54%, the highest certified value to date for a slot die-coated perovskite solar cell. The device also achieved an open circuit voltage of 1.088 V, a short circuit current of 24.9 mA cm2, and a fill factor of 83.1%. The German Fraunhofer ISE CalLab laboratory confirmed this result.
The team also built mini-modules with active areas of 12.7 cm2 and an efficiency of 17.1%.
“A full year of outdoor stability testing with continuous monitoring of the maximum power point is performed on encapsulated devices and shows that these devices maintain close to 100% of their initial performance through the winter and spring, followed by a significant decline performance during the hottest summer months,” the researchers say.
Looking ahead, the researchers plan to extend the technology to devices with larger surface areas and evaluate their performance under various long-term exposure conditions. |
