  Halide perovskites are promising semiconductors for inexpensive,
high-performance optoelectronics. Despite a remarkable defect tolerance
compared to conventional semiconductors, perovskite thin films still show
substantial microscale heterogeneity in key properties such as luminescence
efficiency and device performance. This behavior has been attributed to spatial
fluctuations in the population of sub-bandgap electronic states that act as
trap-mediated non-radiative recombination sites. However, the origin of the
variations, trap states and extent of the defect tolerance remains a topic of
debate, and a precise understanding is critical to the rational design of
defect management strategies. By combining scanning X-ray diffraction beamlines
at two different synchrotrons with high-resolution transmission electron
microscopy, we reveal levels of heterogeneity on the ten-micrometer scale
(super-grains) and even ten-nanometer scale (sub-grain domains). We find that
local strain is associated with enhanced defect concentrations, and
correlations between the local structure and time-resolved photoluminescence
reveal that these strain-related defects are the cause of non-radiative
recombination. We reveal a direct connection between defect concentrations and
non-radiative losses, as well as complex heterogeneity across multiple length
scales, shedding new light on the presence and influence of structural defects
in halide perovskites.
