  Measurements of charge-carrier lifetime in many early-stage thin-film
photovoltaic materials can be arduous due to the prevalence of defects and
limited information about material properties. In this perspective, we give a
brief overview of typical techniques for measuring lifetimes and discuss the
intuition involved in estimating lifetimes from such techniques, focusing on
time-resolved photoluminescence as an example. We then delve into the
underlying assumptions and uncertainties involved in analyzing lifetime
measurements. Finally, we outline opportunities for improving accuracy of
lifetime measurements by utilizing two emerging techniques to decouple
different recombination mechanisms: two-photon spectroscopy, which we
demonstrate on BiI3 thin films, and temperature- and injection-dependent
current-voltage measurements.
