Dictating Organolead Perovskite Nanostructure Size Using Silicon Nanotube Templates

Abstract

A class of alkyl ammonium lead halide structures that readily crystallize as perovskite phases of the generic formula CH3NH3PbX3 have been discovered, and their relative ease of crystallization and formation into robust films have led to the development of an exciting new class of photovoltaic and lasing platforms. To our knowledge, however, synthetic methods that permit an evaluation of the fundamental size dependent properties with the requisite level of control of any of these perovskite structures have not yet been achieved. The key element to achieving feature size control in the synthesis of these perovskite phases is the use of hollow semiconducting silicon nanotubes as templates for perovskite growth; i.e. viewing the nanotube interior as a nanoscale reaction vessel. We have recently reported a facile strategy for the formation of SiNTs of a broadly tunable inner diameter, as well as Si wall thickness. These nanotubes are currently under evaluation for a diverse range of additional uses, such as loading with magnetic nanostructures, drug loading and subsequent delivery, Li storage and discharge phenomena associated with battery technology, etc. In principle, these nanotubes permit structural control of perovskite width through nanotube inner diameter. In this work, we describe the formation of methylammonium lead iodide nanostructures inside porous silicon nanotubes with a wall thickness of 10 nm and possessing inner diameters of either 70 nm or 200 nm. After structural characterization, the photophysical properties of these perovskite nanostructures, in terms of optical absorption and photoluminescence as a function of temperature, are evaluated. Spectroscopic comparisons with relatively larger one-dimensional microwires of the same composition are also carried out. We seek to interrogate not only the presence of size dependent shifts in absorption/emission features associated with a given perovskite structure, but also the effects of physical confinement on possible size-dependent phase behavior of these one dimensional semiconductors.