  Extensive efforts have been undertaken on the photoelectric physics of hybrid
organolead halide perovskites to unveil the reason for the attractive
photovoltaic performance. Yet, the resulting evidences are far from being fully
conclusive. Herein, we provide another direct support for this issue. In
addition to the observation on the conventional band edge at 1.58 eV that
presents a blueshift toward temperature increase, interestingly, we also
observe an unusual optical band edge at 1.48 eV in CH3NH3PbI3 perovskite single
crystals. Contrary to the conventional band edge, this one shows an obvious
redshift toward the enhancement in temperature, in agreement with the Varshni
relation. More interestingly, the unusual band edge exhibits a series of
obvious absorption and photocurrent signals, but the according
photoluminescence signals are not observable. This indicates that this band
edge is particularly beneficial for the photovoltaic effect due to the
inhibited radiative recombination. The kinetics on photo-involved charge
transition and transfer are investigated using the pump-probe photoconductivity
technique, and a changeable band structure model was proposed.
