Deciphering the effect of traps on electronic charge transport properties of methylammonium lead tribromide perovskite

Abstract

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.

Response to Comment on “Eppur si Muove: Proton Diffusion in Halide Perovskite Single Crystals”: Measure What is Measurable, and Make Measurable What is Not So: Discrepancies between Proton Diffusion in Halide Perovskite Single Crystals and Thin Films

“…Quantitative experimental data are available only for electrically active defects, [ 17 ] the density of which in bulk HaP single crystals is estimated to be in the range of or below 10 9 to 10 11 cm −3 from space‐charge‐limited current, [ 18,19 ] complementary Hall effect, [ 20,21 ] deep level transient spectroscopy, [ 22 ] and temperature‐modulated space‐charge‐limited‐current spectroscopy measurements. [ 23–25 ] An outlier based on the last gives a very high defect density of 2 × 10 12 cm −3 , [ 26 ] still 1.5 orders of magnitude too low, while the consensus values from multiple methods are 3–5 orders of magnitude lower than 10 14 cm −3 .…”

Are solution processed CsPbI3 perovskite nanocrystalline films similar to traditional crystalline semiconductors?

“…The electrical field in operando devices exerts a force or 'push' the carriers, enabling an understanding of carrier drift dynamics, in particular, in a long-range transport. For example, in a photoconductive device, the time-resolved photoconductivity techniques such as the time-of-flight photocurrent (17) and photo-CELIV (charge extraction by linearly increasing voltage) characterize the carrier drift properties including carrier mobility, lifetime, and drift length(18) (Fig. 1b).…”

Defect tolerant device geometries for lead-halide perovskites

“…A review of well-studied materials 23 like Si [38][39][40][41] , GaAs [42][43][44] , CdTe 45,46 indicates that asymmetric capture coefficients are common and that its impact on recombination rates in combination with electron and hole concentration have been discussed in widely-used textbooks on the topic of recombination in semiconductors 47 . However, in the field of perovskite photovoltaics measuring capture coefficients [48][49][50] and defect densities [48][49][50] is highly challenging due to the variety of different relevant perovskite materials, the low defect densities, the lack of actual doping and the presence of mobile ions 51,52 . Hence, for lack of better information, a near universal assumption of symmetric capture coefficients is made in studies on perovskite device simulation 53,54 .…”