Harnessing Defect-Tolerance at the Nanoscale: Highly Luminescent Lead Halide Perovskite Nanocrystals in Mesoporous Silica Matrixes

Abstract

Colloidal lead halide perovskite nanocrystals (NCs) have recently emerged as a novel class of bright emitters with pure colors spanning the entire visible spectral range. Contrary to conventional quantum dots, such as CdSe and InP NCs, perovskite NCs feature unusual, defect-tolerant photophysics. Specifically, surface dangling bonds and intrinsic point defects such as vacancies do not form midgap states, known to trap carriers and thereby quench photoluminescence (PL). Accordingly, perovskite NCs need not be electronically surface-passivated (with, for instance, ligands and wider-gap materials) and do not noticeably suffer from photo-oxidation. Novel opportunities for their preparation therefore can be envisaged. Herein, we show that the infiltration of perovskite precursor solutions into the pores of mesoporous silica, followed by drying, leads to the template-assisted formation of perovskite NCs. The most striking outcome of this simple methodology is very bright PL with quantum efficiencies exceeding 50%. This facile strategy can be applied to a large variety of perovskite compounds, hybrid and fully inorganic, with the general formula APbX3, where A is cesium (Cs), methylammonium (MA), or formamidinium (FA), and X is Cl, Br, I or a mixture thereof. The luminescent properties of the resulting templated NCs can be tuned by both quantum size effects as well as composition. Also exhibiting intrinsic haze due to scattering within the composite, such materials may find applications as replacements for conventional phosphors in liquid-crystal television display technologies and in related luminescence down-conversion-based devices.

Strong Quantum Confinement and Fast Photoemission Activation in CH3NH3PbI3 Perovskite Nanocrystals Grown within Periodically Mesostructured Films

“…[4] More recently, powders of porous silica exhibiting a 2D hexagonal mesopore structure have been used as templates to synthesize MAPbI 3 nanocrystals. [14,15] This approach proved to be suitable to attain bright and stable emission whose spectrum could be controlled by the average pore size of the matrix. However, most applications foreseen for hybrid perovskites require the use of thin films of high optical quality, as well as versatility regarding the composition of the scaffold employed.…”

“…Measurements of the quantum yield (QY) return values of QY ≈ 1%, very similar to those previously reported for other confined MAPbI 3 nanocrystals. [14,15] …”

In Situ Fabricated Perovskite Nanocrystals: A Revolution in Optical Materials

“…[77,78] The fabrication process can be carried out by simply mixing the mesoporous silica and perovskite precursor solution under annealing. The resultant PNCs were well embedded into the pores of the mesoporous silica with their size matches perfectly with the pore size from 7.1 nm down to 3.3 nm.…”

“…[79,80] As a result, the solution-processed PNCs with silica template show impressively high quantum efficiency beyond 50%. [78] In another approach, Anaya et The developing roadmap of perovskite nanocrystals. Ex-situ and in-situ fabrication approaches are labeled with red and blue font color, respectively.…”

“…Reproduced with permission. [17,51,53,59,67,78,88] Copyright 2014-2017, American Chemical Society; [57] Copyright 2015, American Association for the Advancement of Science; [58] Copyright 2012, The Chemical Society of Japan; [63,65] Copyright 2016, Springer Nature; [62,[70][71][72]117,121] Copyright 2015-2018, Wiley-VCH. mesostructured films through sol-gel treatment of TiO 2 and SiO 2 precursors within organic templating agents.…”