  Understanding the intrinsic charge transport in organolead halide perovskites
is essential for the development of high-efficiency photovoltaics and other
optoelectronic devices. Despite the rapid advancement of the organolead halide
perovskite in photovoltaic and optoelectronic applications, the intrinsic
charge carrier transport in these materials remains elusive partly due to the
difficulty of fabricating electrical devices and obtaining good electrical
contact. Here, we report the fabrication of organolead halide perovskite
microplates with monolayer graphene as low barrier electrical contact. A
systematic charge transport studies reveal an insulator to band-like transport
transition. Our studies indicate that the insulator to band-like transport
transition depends on the orthorhombic-to-tetragonal phase transition
temperature and defect densities of the organolead halide perovskite
microplates. Our findings are not only important for the fundamental
understanding of charge transport behavior but also offer valuable practical
implications for photovoltaics and optoelectronic applications based on the
organolead halide perovskite.
