Fig. 1. Processing scheme for perovskite thin-film using hot-casting methods and observations
for large-area millimeter-scale crystal grain formation for a perovskite (PbCH3NH3I3–xClx)–
based thin film. (A) Hot-casting scheme for
large-area crystal growth [ITO, indium tin oxide;
FTO, fluorine-doped tin oxide; PEDOT, poly(3,4-
ethylenedioxythiophene) polystyrene sulfonate].
(B) Optical micrographs illustrating grain formation as a function of substrate temperature with
the casting solution maintained at 70°C. (C) Large-area grain formation using casting solvents with
high boiling points. (D) Comparison of grain size
as a function of processing temperature obtained
for the hot-casting and conventional post-annealing
Fig. 2. Solar cell device architecture and performance. (A) Planar device configuration used for this study. (B) J-V curves obtained under AM 1.5 illumination.
(C) Average overall PCE (left) and JSC (right) as a function of crystalline grain
size. The average values were obtained by averaging the PCE and JSC for 25
devices; error bars were calculated by subtracting the average value from max
or min values. Gray box represents the range of PCE values obtained using the
conventional post-annealing process. (D) Average J-V characteristics resulted by
sweeping the voltage from forward to reverse and from reverse to forward bias
demonstrates the absence of hysteresis. These curves were obtained by
averaging 15 sweeps in each direction. (E) J-V curves at different voltage
scan rates in voltage delay time (ms) or V/s again demonstrate negligible
hysteresis. (F) Variation in PCE for 50 measured devices.