posted on 2020-02-20, 16:34authored byJuvinch
R. Vicente, Jixin Chen
Mixed-halide lead
perovskites (MHPs) are promising materials for
photovoltaics and optoelectronics due to their highly tunable band
gaps. However, they phase segregate under continuous illumination
or an electric field, the mechanism of which is still under debate.
Herein we systematically measure the phase segregation behavior of
polymer-encapsulated CH3NH3Pb(BrxI1–x)3 MHPs as a function of excitation intensity and the nominal halide
ratio by in situ photoluminescence microspectroscopy and observe surprising
phase dynamics at the beginning of the illumination. The initial phase
segregation to I-rich and Br-rich phases is observed followed by the
formation of a new mixed-halide phase within several seconds that
has not been reported before. We propose that the photothermal effect
is amplified at the small-size I-rich domains, which significantly
changes the local phase segregation in the otherwise uniform film
within milliseconds after illumination.