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

Abstract

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%.

Investigating the Fabrication of Perovskite Solar Cells by Ultrasonic Spray Coating: A Design of Experiments Approach

“…For the OFAT study, a center point (CP) is selected based on a set of parameters, which previously resulted in high-quality perovskite films . Then, the spray-coating parameters are individually tested by using lower and higher values, while keeping all other parameters at the center point value.…”

“…For the OFAT study, a center point (CP) is selected based on a set of parameters, which previously resulted in high-quality perovskite films. 18 Then, the spray-coating parameters are individually tested by using lower and higher values, while keeping all other parameters at the center point value. The considered parameters are flow rate (FR), hot plate temperature (HPT), path speed (PS), nitrogen pressure for the carrier gas (N2P), number of passes (#Passes), and nozzle-to-sample distance (NTSD).…”

“…The desired perovskite composition is Cs 0.18 FA 0.82 Pb(I 0.94 Br 0.06 ) 3 . This is chosen due to its band gap of 1.6 eV, as demonstrated in a previous study, 18 which is ideal for monolithic tandem application with a CIS bottom cell (1.0 eV). 22 This composition is achieved by preparing precursor solutions with the powders mixed following stochiometric proportions.…”

“…These trends do not follow the observations reported previously in the literature, which revealed an increase in efficiency when perovskite thickness was brought closer to 600 nm by changing only the solution concentration. 18,23 Moreover, the datapoints that have efficiencies higher than 10% despite having thickness above 600 nm were produced with high N 2 pressure (such as datapoints 7.6/8/10 and 7.6/5/10). These findings suggest the presence of additional factors for determining the quality of the produced films.…”

“…Initially, the entire process is reviewed (Figure 1), from substrate cleaning and solution preparation to deposition and post treatment of the film, and process variables are defined. Based on this analysis and previous findings, 18 the variables are evaluated, and experiments are designed. The target of the experiments is to gain further insight on two key steps of the process: the deposition of a wet layer of precursor solution by ultrasonic spray coating, and the gas quenching of the solvent for perovskite crystallization.…”