Highly Photoluminescent and Environmentally Stable Perovskite Nanocrystals Templated in Thin Self‐Assembled Block Copolymer Films

Abstract

Ordered nanostructured crystals of thin organic-inorganic metal halide perovskites (OIHPs) are of great interest to researchers because of the dimensional-dependence of their photoelectronic properties for developing OIHPs with novel properties. Top-down routes such as nanoimprinting and electron beam lithography are extensively used for nanopatterning OIHPs, while bottom-up approaches are seldom used. Herein, developed is a simple and robust route, involving the controlled crystallization of the OIHPs templated with a self-assembled block copolymer (BCP), for fabricating nanopatterned OIHP films with various shapes and nanodomain sizes. When the precursor solution consisting of methylammonium lead halide (MAPbX 3 , X = Br − , I − ) perovskite and poly(styrene)-block-poly(2-vinylpyridine) (PS-b-P2VP) is spin-coated on the substrate, a nanostructured BCP is developed by microphase separation. Spontaneous crystallization of the precursor ions preferentially coordinated with the P2VP domains yields ordered nanocrystals with various nanostructures (cylinders, lamellae, and cylindrical mesh) with controlled domain size (≈40-72 nm). The nanopatterned OIHPs show significantly enhanced photoluminescence (PL) with high resistance to both humidity and heat due to geometrically confining OIHPs in and passivation with the P2VP chains. The self-assembled OIHP films with high PL performance provide a facile control of color coordinates by color conversion layers in blue-emitting devices for cool-white emission.

Improving Performance of Nonvolatile Perovskite‐Based Photomemory by Size Restrain of Perovskites Nanocrystals in the Hybrid Floating Gate

“…[45] The absence of the absorption peak from MAPbBr 3 NCs in the 1:2 and 2:1 of MAPbBr 3 /P2VP hybrid films suggests the incomplete crystallization of MAPbBr 3 and it is an important evidence of the strong interaction existing between P2VP and perovskite precursors. [40] As compared to the case of the PS-based films, we can conclude that such interaction originates from the N atom in P2VP since, which coordinates with Pb 2+ in PbBr 2 to retard the perovskite crystallization. [46] The interaction between P2VP and PbBr 2 can also be supported by the absorption peak at ≈320 nm, which is consistent with the absorption profile of P2VP-PbBr 2 film as shown in the insert in Figure 2b.…”

“…However, the P2VP possesses intense interaction with perovskite precursor through acid-base coordination, which would retard the crystallization process of perovskite crystals and suppress their growth. [40] In this regard, the size of perovskite NCs formed in the P2VP film become smaller and will be better embedded inside the polymer matrix. The smooth surface alongside with the embedment of small size perovskite NCs is beneficial to enhance the photo-memory behavior of the derived device as discussed earlier.…”

“…[39] Owing to the intense interaction with perovskite precursors, it further restrains the growth of perovskite NCs with a size below 10 nm and promotes the uniform distribution of discrete perovskite NCs. [40,41] Such conspicuous change is evident as compared to the case of using PS as the host matrix. [42] The P2VP/perovskite (P2VP/PVSk) derived photomemory possesses a much shorter responsive time (5 s light illumination) to write and store charge than that (60 s) of the PS/PVSK-based device; meanwhile, the P2VP/PVSK device only requires a very low voltage of −1 V to achieve same electrical performance as the PS/PVSK device do that requires −60 V. Besides, owing to the well embedment of perovskite NCs inside the P2VP matrix, this hybrid folating gate possesses high robustness against water and oxygen to result in good device's long-term stability over 6 months.…”

Multifunctional Structured Platforms: From Patterning of Polymer-Based Films to Their Subsequent Filling with Various Nanomaterials

“…Examples of etching procedures include UV ozone [ 243 ], oxygen [ 241 , 243 ], nitrogen [ 241 ], or other types [ 239 , 241 ] of plasma etching, CO 2 and Cl 2 /O 2 reactive ion etching [ 205 ], etching in alkaline solutions [ 204 ]), etc. As a result, BCP templates made from materials such as poly(cyclohexylethylene)- b -poly(lactide) [ 242 ], polystyrene- b -poly(2-vinyl pyridine) [ 233 , 245 ], polystyrene- b -polymethyl methacrylate [ 238 , 246 ], polystyrene- b -polydimethylsiloxane [ 239 , 247 , 248 ], or others [ 205 ] lead to the fabrication of a large variety of versatile surface relief patterns of different material nature. Examples include (metal) nanodots [ 240 , 249 , 250 ], bimetallic NP arrays [ 251 ], perovskite cylinders, lamellae or cylindrical mesh [ 245 ], 2D metal/silicon nanowires [ 206 , 249 ], metal oxide arrays [ 242 ] of nanorods [ 244 ] or nanorings [ 243 ], and more [ 205 , 252 ].…”

Orientation-Dependent Conversion of VLS-Grown Lead Iodide Nanowires into Organic-Inorganic Hybrid Perovskites

“…has been a focus of research interest, stemming from its superior physical properties such as high absorption coefficients and long carrier diffusion length [ 1 , 2 ]. The low cost of raw materials and the ease of preparation in which the crystallization is readily attainable in the solution phase at room temperature [ 3 , 4 , 5 ] have led the extensive studies regarding the OIHPs material to diverse applications including photonic [ 6 , 7 , 8 ], electronic [ 9 , 10 ], and optoelectronic [ 11 , 12 ] devices. Meanwhile, the efforts to fabricate OIHPs with various morphologies in low dimension forms also have been tried, especially in nanoparticles, thin films, and nanowires.…”