Velocity and size measurement of droplets from an ultrasonic spray coater using Photon Correlation Spectroscopy and Turbidimetry

We have developed a combination of light scattering techniques to study and characterize droplets of a ultrasonic spray printer or coater in flight. For this economically relevant printer there is so far no reliable technique to systematically adjust the experimental parameters. We have combined photon correlation spectroscopy and turbidimetry to determine size and speed of the droplets depending on parameters of the printing process as viscosity, concentration and speed of the driving shroud gas. Our method allows to predetermine these parameters to control the properties of the printed films as e.g. thickness from tens of nanometers to micrometers

A study of quenching approaches to optimize ultrasonic spray coated perovskite layers scalable for PV

Perovskite materials have gathered increased interest over the last decade. Their rapidly rising efficiency, coupled with the compatibility with solution processing and thin film technology has put perovskite solar cells (PSC) on the spotlight of photovoltaic research. On top of that, band gap tunability via composition changes makes them a perfect candidate for tandem applications, allowing for further harvest of the solar irradiation spectrum and improved power conversion efficiency (PCE). In order to convert all these advantages into large scale production and have increased dissemination in the energy generation market, perovskite fabrication must be adapted and optimized with the use of high throughput, continuous processes, such as ultrasonic spray coating (USSC). In this paper we investigate the ultrasonically spray coated perovskite layers for photovoltaic applications, with particular focus on the quenching-assisted crystallization step. Different quenching techniques are introduced to the process and compared in terms of final layer morphology and cell performance. Finally, gas quenching is used with the large-scale-compatible deposition and allows the production of perovskite solar cells with PCE >15%