Perovskite solar cells have shown their potential for multijunction applications due to their tunable bandgap. This research focuses on triple cation (3C) wide bandgap perovskites ranging from 1.6 to 1.76 eV, an ideal bandgap choice for 2-terminal tandems. The bandgap is changed via the X-site substitution of iodine (I) with bromine (Br) and via cation substitution, with various concentrations of cesium (Cs), methylammonium (MA), and formamidinium (FA). As a result, it is seen that cation engineering is a viable solution to fine-tune the bandgap and prevent a photoinduced segregation. Moreover, a champion efficiency of 18.3% is reported with a 1.67 eV bandgap.

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%.

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