4.3. Analysis
A field emission scanning electron microscope (FE-SEM, SU-70, Hitachi)
was used to examine the morphology and thickness of the device
configurations while an X-ray diffractometer (Rigaku Corp., D/max-2500,
Tokyo, Japan) was used to confirm the crystallinity of
TiO2 and perovskite layers. To measure the
transmittance, a UV-Vis spectrophotometer (Jasco International Co.,
Ltd., V-730, Tokyo, Japan) was used and the infrared spectra were
recorded on the Fourier-transform infrared (FTIR) spectrometer (Nicolet
6700, Thermo Scientific) in the range of 600 – 4000
cm-1. Then, a solar simulator (Newport Corp., Model
94022A, Irvine CA, USA) with a source meter (Keithley Instruments Inc.,
Keithley 2400, Cleveland, OH, USA) under AM 1.5 illumination (100
mW/cm2) was used to characterize the photovoltaic
properties of PSCs. The characterization was carried out at the Future
Energy Convergence Core Center (FECC). All devices were measured by
masking 0.1256 cm2 of the active area with a mask
under argon condition. The solar cell quantum efficiency measurement
system (PV Measurements Inc., QEX7, Point Roberts, WA, USA) was also
used to measure the incident photon to electron conversion efficiencies.
Electrochemical impedance spectroscopy was performed using a
potentiostat (Solartron 1287) and frequency response analyzer (Solartron
1260) in the range of 10-2 and 106Hz. The measurements were analyzed using the ZView software (Solartron
Analytical) with the aid of appropriate equivalent circuit, where the
applied bias voltage and the amplitude of alternating current was set at
the open circuit voltage (Voc ). The impedance
measurements were carried out at open-circuit potential under AM 1.5
illumination.