Researchers from Czech Republic's Charles University, University of Tennessee and Oak Ridge National Laboratory in the U.S have explored the dynamics of free holes in methylammonium lead tribromide (MAPbBr3) single crystals using time-of-flight (ToF) current spectroscopy. The team's results provide insights on the charge transport properties of perovskite semiconductors.
By combining ToF spectroscopy and Monte Carlo simulation, three energy states were detected in the bandgap of MAPbBr3. In addition, the team found the trapping and detrapping rates of free holes ranging from a few microseconds to hundreds of microseconds. It was revealed that a strong detrapping activity of traps exists.
The team's results showed that traps have a notable impact on the free carrier transport and the collection efficiency in MAPbBr3 perovskite devices.
The team proposed a new model for the effective mobility, to describe the delaying effect of traps on the charge transport properties of MAPbBr3 single crystals.
The results demonstrated that the role of traps should be carefully considered in the study of transport properties of OMHP devices, such as the assessment of drift mobility, lifetime, and mobility-lifetime product.