Metal halide perovskites for filterless photodetectors

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Photodetectors are a critical part of optical communication systems for highly efficient light-to-current conversion. Metal halide perovskite semiconductor materials are the perfect match for this technology owing to their broadly tunable compositions, compatibility with simple solution processing combined with their strong light absorption and high charge carrier mobilities. In this project perovskite photodetectors will be fabricated to achieve light detection from the ultra-violet (UV) to the near infra-red (NIR) regions of the electromagnetic spectrum. This will be achieved by bandgap engineering the perovskite through compositional variation and taking advantage of recent developments within our research lab to explore previously unachievable thick absorber layers.1,2 Combined with a suite of optoelectronic measurements the project will aim to deliver composition and thickness related figures of merit for dark current, responsivity and detectivity allowing a holistic overview of structure-processing-property relationships in these exciting materials.Metal halide perovskite semiconductors (PSCs) have seen rapid progress in their optoelectronic applications due to their broadly tunable compositions achieved using simple processing approaches, their strong light absorption and high charge carrier mobility. The current success of PSCs is mainly driven in photovoltaics (PVs), with power conversion efficiencies (PCEs) now in excess of 25%.3 Conversely, perovskite photodetectors (PPD), a technology based on photodiodes and thus closely related to PVs, have not experienced a similar trajectory of growth, mainly due to the lack of understanding of how to simultaneously control critical device parameters such as diode rectification, external quantum efficiency (EQE) and temporal responsivity.4 In this project, by tuning the composition of the perovskite active layer and its thickness, PPDs will be fabricated to achieve detection spanning from the UV to the NIR part of the electromagnetic spectrum. The photodiodes will be fabricated in cleanroom conditions using state-of-the-art deposition methods. The performances of PPDs will be evaluated via current-voltage measurements in the dark and under light illumination to evaluate the rectification of the diodes and their dark-current (Jd). Moreover, EQE and specific detectivity measurements will be carried out to evaluate the light-to-current conversion of the devices. The aim of this project is to correlate i) the composition variation of the perovskite active layer with the Jd of the devices and ii) the thickness variation with the Jd of the photodiodes. These aspects are of the utmost importance for real-world application, where low Jd is desired.1. Du, T. et al. Light-Intensity and Thickness Dependent Efficiency of Planar Perovskite Solar Cells: Charge Recombination versus Extraction. J. Mater. Chem. C 2020, 8, 12648.2. Du, T. et al Aerosol Assisted Solvent Treatment: A Universal Method for Performance and Stability Enhancements in Perovskite Solar Cells, Adv. Energy Mater. 2021, 2101420, 1.3. Zheng, X. et al. Managing grains and interfaces via ligand anchoring enables 22.3%-efficiency inverted perovskite solar cells. Nat. Energy 5, 131-140 (2020).4. Miao, J. & Zhang, F. Recent progress on highly sensitive perovskite photodetectors. J. Mater. Chem. C 7, 1741-1791 (2019).McMeekin, D. P. et al. A mixed-cation lead halide perovskite absorber for tandem solar cells. Science (80-. ). 351, 151-155 (2016).