Confining Metal-Halide Perovskites in Nanoporous Thin Films

Controlling size and shape of semiconducting nanocrystals advances nanoelectronics and photonics. Quantum confined, inexpensive, solution derived metal halide perovskites offer narrow band, color-pure emitters as integral parts of next-generation displays and optoelectronic devices. We use nanoporous silicon and alumina thin films as templates for the growth of perovskite nanocrystallites directly within device-relevant architectures without the use of colloidal stabilization. We find significantly blue shifted photoluminescence emission by reducing the pore size; normally infrared-emitting materials become visibly red, green-emitting materials cyan and blue. Confining perovskite nanocrystals within porous oxide thin films drastically increases photoluminescence stability as the templates auspiciously serve as encapsulation. We quantify the template-induced size of the perovskite crystals in nanoporous silicon with microfocus high-energy X-ray depth profiling in transmission geometry, verifying the growth of perovskite nanocrystals throughout the entire thickness of the nanoporous films. Low-voltage electroluminescent diodes with narrow, blue-shifted emission fabricated from nanocrystalline perovskites grown in embedded nanoporous alumina thin films substantiate our general concept for next generation photonic devices.