posted on 2020-08-13, 19:07authored byXingtian Yin, Yuxiao Guo, Jie Liu, Wenxiu Que, Fei Ma, Kewei Xu
The
photoinduced phase segregation (PIPS) of mixed-halide perovskites
(MHPs), due to halogen migration, has reaped considerable attention
for its retroaction on film photostability and photovoltaic output.
Nevertheless, the original mechanism is still unclear. Herein, taking
the representative CsPbIBr2 material as an example, a confocal
laser scanning microscope (CLSM) technique was adopted to track the
PIPS and dark recovery procedures. Besides the aggregation of iodide-rich
(I-rich) domains at grain boundaries (GBs), some sporadic iodide “islands”
with a swifter light response also appear throughout the polycrystalline
films. It illustrates again that GBs are not essential for iodide
aggregation. Furthermore, the iodide “islands” have
substantial influence on a device’s open-circuit voltage (Voc), resulting in an obvious plunge in the first
tens of seconds. Results reveal the internal reason for the failure
to reach the larger Voc outputs expected
from wide-bandgap perovskites. Importantly, this finding can help
promote the exploration of an efficient means to stabilize MHPs.