  The reversible phase transition between orthorhombic and cubic phases is
demonstrated in all-inorganic perovskite CsPbIBr2 grown by a dual-source
vapor-deposition method. The phase transition is actuated via heating and
moisture exposure. The different crystal structures of two phases result in
distinct optoelectronic properties including optical absorption, refractive
index, and carrier transport. The perovskite photodetector array for the
non-volatile rewritable optical memory application is further investigated. A
near-infrared (NIR) laser ({\lambda} = 1064 nm) is used to selectively heat
photodetector pixels through the photothermal effect of the interfacial Ag
electrodes, resulting in an optically absorbing perovskite phase for the
photodetectors. The locations of specific laser-written pixels can be read out
by measuring their photocurrents, and the stored optical information can also
be erased by moisture exposure. Finally, a proof-of-concept optical imaging
application has been demonstrated using perovskite photodetector arrays
fabricated on flexible PET substrates. These results show promising
applications of vapor-deposited inorganic perovskite for optical memory and
image sensors, with unique potential for low-cost manufacturing of large-area
and/or flexible devices.
