Stable Efficient Methylammonium Lead Iodide Thin Film Photodetectors with Highly Oriented Millimeter-Sized Crystal Grains

Abstract

The size of crystal grains in lead halide perovskite thin films remains a vital design feature for durable optoelectronic devices. With larger crystals and reduced grain boundaries per surface area, the stability of the structures improves as degradation, caused by moisture and oxygen percolating into the grain boundaries, is minimized. Thus far, large scale continuous lateral films of methylammonium lead iodide (MAPbI3) with macroscale crystal grains compatible with thin film (<1 μm thick) solar cells and photodetectors have not been reported. Herein, we employ meniscus-guided blade coating technique to grow thin films of highly oriented millimeter-size MAPbI3 crystals, resulting in over an order of magnitude responsivity enhancement over spin-coated films in lateral photoconductors with channel lengths over 100 μm. Furthermore, the blade-coated MAPbI3 thin films exhibit anisotropic higher conductivity along crystal grains over a millimeter range. With crystals orders of magnitude larger in size, and with no additive treatment or additional layers, blade-coated devices manifest improved stability and retain over 80% of their performance tested in ambient air for over 300 h in comparison to spin-coated devices that reach less than 50% of their original peformance within the first 36 h.