The intrinsic low sensitivity of nuclear magnetic resonance
(NMR)
experiments limits their utility for structure determination of materials.
Dynamic nuclear polarization (DNP) under magic angle spinning (MAS)
has shown tremendous potential to overcome this key limitation, enabling
the acquisition of highly selective and sensitive NMR spectra. However,
so far, DNP methods have not been explored in the context of inorganic
lead halide perovskites, which are a leading class of semiconductor
materials for optoelectronic applications. In this work, we study
cesium lead chloride and quantitatively compare DNP methods based
on impregnation with a solution of organic biradicals with doping
of high-spin metal ions (Mn2+) into the perovskite structure.
We find that metal-ion DNP provides the highest bulk sensitivity in
this case, while highly surface-selective NMR spectra can be acquired
using impregnation DNP. The performance of both methods is explained
in terms of the relaxation times, particle size, dopant concentration,
and surface wettability. We envisage the future use of DNP NMR approaches
in establishing structure–activity relationships in inorganic
perovskites, especially for mass-limited samples such as thin films.