Halide perovskites have undergone remarkable developments as highly efficient optoelectronic materials for a variety of applications. Several studies indicated the critical role of defects on the performance of perovskite devices. However, the parameters of defects and their interplay with free charge carriers remain unclear. In this study, we explored the dynamics of free holes in methylammonium lead tribromide (MAPbBr3) single crystals using the time-of-flight (ToF) current spectroscopy. By combining ToF spectroscopy and Monte Carlo simulation, three energy states were detected in the bandgap of MAPbBr3. In addition, we found the trapping and detrapping rates of free holes ranging from a few microseconds to hundreds of microseconds. Contrary to previous studies, we revealed a strong detrapping activity of traps. We showed that these traps substantially affect the transport properties of MAPbBr3, including mobility and mobility-lifetime product. Our results provide an insight on charge transport properties of perovskite semiconductors.

The interaction of free carriers with defects and some critical defect properties are still unclear in methylammonium lead halide perovskites (MHPs). Here, a multi-method approach is used to quantify and characterize defects in single crystal MAPbI 3 , giving a cross-checked overview of their properties. Time of flight current waveform spectroscopy reveals the interaction of carriers with five shallow and deep defects. Photo-Hall and thermoelectric effect spectroscopy assess the defect density, cross-section, and relative (to the valence band) energy. The detailed reconstruction of free carrier relaxation through Monte Carlo simulation allows for quantifying the lifetime, mobility, and diffusion length of holes and electrons separately. Here, it is demonstrated that the dominant part of defects releases free carriers after trapping; this happens without non-radiative recombination with consequent positive effects on the photoconversion and charge transport properties. On the other hand, shallow traps decrease drift mobility sensibly. The results are the key for the optimization of the charge transport properties and defects in MHP and contribute to the research aiming to improve perovskite stability. This study paves the way for doping and defect control, enhancing the scalability of perovskite devices with large diffusion lengths and lifetimes.

Emerging metal-halide perovskites (MHPs) have shown advanced charge transport properties suitable for application in solar cells, photodetectors, and many more. While the past decade witnessed tremendous progress in MHPs, very little is known about the origin of defects and their effect on carrier lifetime. In this study, we compare hybrid and all-inorganic MHPs prepared by inverse temperature solution and high-temperature melt growth to explore the influence of material preparation on the formation of defects. The presence of a low concentration of vacancies was shown in all MHPs regardless of their synthesis method demonstrated by the interaction of positron particles with vacancies and lattices of MHPs and explained by ab initio simulation of positron annihilation. We combined the Raman, Fourier transform infrared (FTIR), and positron annihilation spectroscopy methods to establish the nature of imperfections in MHPs grown using different methods. Our Raman and FTIR results reveal that only the solution-grown crystals are prone to the incorporation of a solvent in bulk during synthesis. In vast majority of studies, the charge carrier lifetime is explored using photoluminescence (PL) spectroscopy as it is a readily available method. However, PL is very sensitive to both bulk and surface recombination phenomena. Combining current waveform time-of-flight and time-resolved photoluminescence spectroscopy methods, the bulk recombination differs by a factor of 2 from crystals grown by solution versus high-temperature melt. The results propose that solvent trapping matters, not intrinsic defects. The study also suggests potential pathways for further improvement of hybrid and all-inorganic MHPs.