Scalable Processes to Manufacture Perovskite Solar Modules
Perovskite semiconductors combine excellent optoelectronic properties with the ease of solution-processing and co-evaporation as well as low-cost precursor materials. However, the large-scale deposition of pinhole-free and high-quality thin films introduces challenges. In order to advance the scale-up of perovskite solar modules, our team researches these technologies and processes:
Scalable fabrication of solution-processed perovskite thin films
For the solution-based deposition of large-area pinhole-free perovskite thin films, the precursor solutions are printed and must subsequently be dried and crystallized in a controlled way. Our team developed inkjet-printed, blade-coated, slot-die coated perovskite solar cells     . A highlight of our team is the demonstration of record power conversion efficiencies in inkjet-printed perovskite solar cells in 2019 . In this study, we developed inkjet-printed perovskite layers of exceptional thickness (> 1 µm) with large columnar crystal structure.
Figure 1: Schematic illustration of the inkjet printing process. Image of an inject-printed perovskite KIT logo on a PET substrate. Inkjet-printed luminescent down-shifting (LDS) layers on top of perovskite layers.
Process control and in situ characterization of solution-processed perovskite thin films
Controlling the nucleation and crystal growth of pinhole-free perovskite thin films over large areas is not only an engineering challenge, but requires understanding the drying dynamics and entangled processes during the formation of the multi-crystalline thin films . For this reason, we are particularly interested in applying in situ optical spectroscopy to analyse the drying, nucleation and crystallization processes. A highlight of our team in this field is our study on in situ characterization of the drying dynamics of blade coated perovskite solar cells . The study reports on a model for the drying dynamics, leading to improved solar cell performance. In order to expand these research activities, we have established a dedicated in situ characterization platform of solution-processed perovskite thin films. This unique platform combines interferometry, (transient) photoluminescence, white light interferometry, and Raman spectroscopy.
Figure 2: The individual steps of solution-based deposition of perovskite thin films. Optimizing the nucleation and crystallization is important for high-quality perovskite absorbers.
Evaporated perovskite thin-film photovoltaics
Vacuum-based deposition techniques are a common route for the fabrication of large-area thin-film photovoltaics, providing excellent homogeneity and high fabrication yield. In the field of perovskite photovoltaics, however, co-evaporated vacuum-based deposition of perovskite thin films is less researched and limited so far to a few material compositions. Consequently, the demonstrated power conversion efficiencies lag behind solution-processed devices. Our team develops all-evaporated perovskite photovoltaics as a promising approach toward industrial large-scale fabrication  . Our labs are equipped with dedicated evaporation systems that enable co-evaporation of complex compositions of perovskite semiconductors (e.g. multi-cation and wide-bandgap candidates) and deposition on areas up to 6 inches.
Figure 3: Gloveboxes of our upscaling laboratory and photograph of an evaporated perovskite thin-film.
Perovskite thin-film solar modules
We offer a baseline platform for processing solar modules on areas up to 20x20 cm². Highlights of this work are our all-evaporated perovskite solar module from 2021  and our work on perovskite/CIGS tandem solar modules .
Figure 4: Large-scale all-evaporated perovskite solar modules and photo of perovskite/CIGS tandem solar modules.