  Polarizers are ubiquitous components in optoelectronic devices of daily use
as displays, optical sensors or photographic cameras, among others. Yet the
control over light polarization is an unresolved challenge as the main drawback
of the current display technologies relays in significant optical losses. In
such a context, organometal halide perovskites can play a decisive role given
their flexible synthesis with under design optical properties . Therefore,
along with their outstanding electrical properties have elevated hybrid
perovskites as the material of choice in photovoltaics and optoelectronics.
Among the different organometal halide perovskite nanostructures, nanowires and
nanorods have lately arise as key players for the control of light polarization
for lighting or detector applications. Herein, we will present the
unprecedented fabrication of highly aligned and anisotropic methylammonium lead
iodide (MAPI) perovskite nanowalls by Glancing Angle Deposition of PbI2 under
high vacuum followed by CH3NH3I deposition at normal angle. Our approach offers
a direct route for the fabrication of perovskite nanostructures virtually on
any substrate, including on photovoltaic devices. The unparalleled alignment
degree of the perovskite nanowalls provides the samples with strong anisotropic
optical properties such as light absorption and photoluminescence, the latter
with a maximum polarization ratio of P=0.43. Furthermore, the implementation of
the MAPI nanowalls in photovoltaic devices provides them with a
polarization-sensitive response, with a maximum photocurrent difference of 2.1
% when illuminating with the near-infrared range of the solar spectrum (>700
nm). Our facile vacuum-based approach embodies a milestone in the development
of last generation polarization-sensitive perovskite-based optoelectronic
devices such as lighting appliances or self-powered photodetectors.
