Flexible array of high performance and stable formamidinium-based low-n 2D halide perovskite photodetectors for optical imaging

Metal halide perovskites are attracting increasing attention as photodetectors (PDs) materials due to their excellent photoelectric properties. However, integrating perovskite to realize high-resolution perovskite pixel arrays remains critical to enable practical devices. Herein, we demonstrate a high-responsivity and stable 10 x 10 flexible PDs array based on formamidinium-based quasi-2D Ruddlesden-Popper (BA)2FAPb2I7 (n = 2) (BA= butylammonium, C4H9NH3+) perovskite elements for image sensing. The high-performance (BA)2FAPb2I7 arrays are synthesized on a polyethylene terephthalate (PET) flexible substrate, on a large scale, high quality, and controllable manner by introducing Au nanoparticles to enhance film quality upon the annealing process and recrystallization by applying formamidinium chloride (FACl) post-treatment to reduce perovskite film defects, combined with an innovative SiO2-assisted hydrophilic and hydrophobic surface treatment strategy. The prepared flexible PDs arrays show excellent optoelectronic properties with high responsivity (5.9 A W-1), a detectivity of 8.2 x 1012 Jones, large on/off current ratio (up to 3 x 104), ultimate response speed (12.8 mu s/10.1 mu s), and wide spectral response range. In addition, the device shows outstanding mechanical stability under severe bending (theta = 120 degrees) and excellent folding durability after thousands of bending cycles. It also exhibits excellent environmental stability with only a slight degradation of photoresponse after 100 days of storage under the ambient environment. Finally, the integrated flexible PDs arrays can be used as an effective visible light image sensor with good spatial resolution, paving a multifunctional and competitive way for future wearable sensors and artificial vision systems.One-sentence summary: Low-dimensional halide perovskite layers pixelized on a polyethylene terephthalate (PET) flexible substrate provide high performance photodetectors.