Fully printable perovskite devices

Abstract

Halide perovskites are an emerging class of semiconductors materials. They possess excellent optoelectronic properties, have high defect tolerance, long carrier diffusion lengths and large absorption coefficients. Halide perovskites also support a wide range of switching physics, which makes them suitable for application in neuromorphic systems, in particular memristors. Additive Manufacturing (AM) is being researched as an improvement over conventional manufacturing in ways such as increased customisability, little to no post-processing and reduction of material waste. Printed electronics is a product market that benefits from AM and has been forecasted to continue growing over the next decade. Of the current AM technologies being used in the field of printable electronics, Direct Ink Writing (DIW) has not been actively explored, and even less so for halide perovskite electronics. In this project, we aim to leverage the extrusion technique of DIW and its ability to work with a wide range of ink viscosities to pattern halide perovskite memristors. We will approach this project with solvent engineering and printing parameter optimisation to print the perovskite memristors, characterise the morphology of the prints and memristive behaviour of the prints via electrical measurements. Preliminary experiments yielded prints with discrete perovskite islands and, in general, a very sparse microstructure. An additional approach of substrate engineering was required, to be used in conjunction with solvent engineering and print parameter optimisation to improve the compactness of the perovskite prints. Substrate engineering involved the use of a mesoporous Titanium Dioxide (mTiO2) template. After characterising the microstructure of the perovskite prints on the mTiO2, the compactness of the perovskite grains were observed to have improved. Electrical analysis was then conducted on the perovskite devices. Memristive behaviour was indicated via the hysteresis loops measured. This indicated the effectiveness of substrate engineering. The morphology of the fully printed devices was characterised and observed to be similar to those of the devices that included the spin-coating step for the mTiO2. Electrical analysis on the fully printed devices also indicated memristive behaviour, proving the functionality of fully printed perovskite devices.Bachelor's degre