Fabrication of Monolithic Perovskite-on-Chalcogenide Photovoltaic Tandem Devices by Ultrasonic Spray Coating

Abstract

The worldwide push towards sustainable energy sources, driven by concerns over climate change and economic stability, underscores the significance of solar power as a cornerstone of the global energy landscape. Photovoltaic generation stands out as a clean and abundant alternative to traditional fossil fuels, offering a pathway to generate electricity while mitigating the emission of greenhouse gases. To accelerate the energy transition and meet the escalating demands driven by the ongoing electrification trend, the capacity for photovoltaic energy generation must be increased substantially. Technological innovations aimed at developing more cost-effective PV technologies with enhanced conversion efficiencies are key drivers in this endeavor. Within the realm of solar energy research, perovskite solar cells have emerged as a promising technology due to their high efficiency, bandgap tunability, and simple fabrication. These characteristics position perovskite as an ideal candidate for multijunction applications, where the combination of multiple active layers extends the absorption of incident light to boost device performance. While many technologies are suitable for the combination with perovskites, CIGS cells have particular advantages. Both perovskite and CIGS solar cells are thin-film technologies, enabling lightweight and flexible applications. Moreover, CIGS technology boasts a long history of development and optimization spanning over four decades, rendering it a well-established player in the PV market. The ability to fine-tune the bandgaps of both materials facilitates precise adjustment of absorption ranges and current matching, essential for their integration into 2-terminal monolithic devices. The main challenge for the fabrication and commercialization of monolithic perovskite-on-CIGS devices lies in the deposition of the perovskite layer, especially due to the typically rough top surface of CIGS solar cells. Ultrasonic spray coating is a promising solution, offering a cost-effective, scalable, and high-throughput method for perovskite deposition. Additionally, the technique enables the coating of textured and rough surfaces, as well as 3D objects, further enhancing its applicability and versatility in PV fabrication processes. This doctoral research project delves into the deposition of perovskite layers by ultrasonic spray coating for the fabrication of monolithic perovskite/CIGS tandem cells. By leveraging the advantages of this technique and complementing it with gas quenching for film crystallization, the study achieves the production of high-quality perovskite layers. Furthermore, deposition process is employed in the fabrication of perovskite solar cells, both as standalone single junction devices and as the top cell component in monolithic multijunction configurations. Notably, in the latter scenario, the research showcases the potential of ultrasonic spray coating to deposit conformal perovskite layers even on rough substrates. The outcomes of this investigation offer invaluable insights into the scalable fabrication of perovskite films, thereby advancing the journey of perovskite solar cells one step closer towards commercialization.