Abstract
The manufacturing of devices from methylammonium-based perovskites asks for reliable and scalable processing. As solvent engineering is not the option of choice to obtain homogeneous layers on large areas, our idea is to ‘upgrade’ a non-perfect pristine layer by recrystallization in a thermal imprint step (called ‘planar hot pressing’) and thus to reduce the demands on the layer formation itself. Recently, imprint has proven both its capability to improve the crystal size of perovskite layers and its usability for large area manufacturing. We start with methylammonium lead bromide layers obtained from a conventional solution-based process. Acetate is used as a competitive lead source; even under perfect conditions the resulting perovskite layer then will contain side-products due to layer formation besides the desired perovskite. Based on the physical properties of the materials involved we discuss the impact of the temperature on the status of the layer both during soft-bake and during thermal imprint. By using a special imprint technique called ‘hot loading’ we are able to visualize the upgrade of the layer with time, namely a growth of the grains and an accumulation of the side-products at the grain boundaries. By means of a subsequent vacuum exposition we reveal the presence of non-perovskite components with a simple inspection of the morphology of the layer; all experiments are supported by X-ray and electron diffraction measurements. Besides degradation, we discuss recrystallization and propose post-crystallization to explain the experimental results. This physical approach towards perovskite layers with large grains by post-processing is a key step towards large-area preparation of high-quality layers for device manufacturing.
Highlights
The properties of semiconducting organic–inorganic perovskites are remarkable
Our focus is an upgrade of the perovskite layer by thermal imprinting, and one issue in this context is the impact of the preparation conditions of the starting layer on upgrading
The overall length of the grain-boundaries decreases; this is in accord with holes of growing size but decreasing density, as documented by the overall area occupied by holes which remains largely constant during recrystallization (Table 2); the excess material contained in the layers is mainly rearranged between the growing crystalline regions
Summary
The properties of semiconducting organic–inorganic perovskites are remarkable. Some representatives of this class combine two key qualifications, referring to the processing capabilities on the one hand and the physical properties on the other hand. Important thermodynamic data (melting point, boiling point and vapour pressure) of all components of interest are summarized in Table 1 indicating, in addition, the physical phase at the temperatures and pressures characteristic of our investigation, at the soft-bake temperatures TSB (referring to preparation of the pristine layers) and the imprint temperature Ti (referring to the upgrade), as well as under exposition to vacuum (VAC, referring to the status/consistence testing). In contrast to the multitude of chemical strategies reported in literature the actual investigation represents a physical approach towards high-quality perovskite layers that is up-scalable, namely upgrading by thermal imprint. This engineering approach may contribute to pave the way for the reproducible manufacturing of devices based on perovskite thin films in the future
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
