Abstract
Hybrid organic-inorganic lead halide perovskites have attracted broad interest because of their unique optical and electronic properties, as well as good processability. Thermal properties of these materials, often overlooked, can provide additional critical information for developing new methods of thin film preparation using, for example, melt processing-i.e., making films of hybrid perovskites by solidification of a thin layer of the melt liquid. We demonstrate that it is possible to tune the melting temperature of layered hybrid lead iodide perovskites over the range of more than 100 degrees by modifying the structures of alkylammonium-derived organic cations. Through the introduction of alkyl chain branching and extending the length of the base alkylammonium cation, melting temperatures of as low as 172 °C can be achieved and high quality thin films of layered hybrid lead iodide perovskites can be made using a solvent-free melt process with no additives and in ambient air. Additionally, we show that a similar concept can be translated to the corresponding layered bromides, with slightly higher observed melting temperatures. The design rules established here can guide the discovery of new melt-processable perovskite materials for low-cost high performance devices.
Highlights
Over the past few years, increasing interest and research efforts have been directed towards hybrid organic–inorganic perovskite (HOIP) materials, lead-halide-based systems, because of their novel electronic and optical properties.[1]
To further investigate the applicability of the proposed design rules over a wider range of hybrid structures and to create material candidates that melt at much lower temperature, we extended our effort into the alkylammonium-based layered lead halide perovskites
Six alkylammonium cations (n-butylammonium (n-ba), secbutylammonium (1-Me-pa), 1-methyl-butylammonium (1-Meba), n-hexylammonium (n-ha), 1-methyl-hexylammonium (1Me-ha), 2-ethyl-hexylammonium (2-Et-ha)) with different chain length and structural motif were chosen and the corresponding layered lead iodide perovskite compounds were synthesized via slow cooling from concentrated hydriodic acid solutions
Summary
Over the past few years, increasing interest and research efforts have been directed towards hybrid organic–inorganic perovskite (HOIP) materials, lead-halide-based systems, because of their novel electronic and optical properties.[1]. We demonstrate that it is possible to tune the melting temperature of layered hybrid lead iodide perovskites over the range of more than 100 degrees by modifying the structures of alkylammonium-derived organic cations.
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