  A novel triphenylamine-based hole transport material (HTM) with a carboxyl
anchoring group (TPATC) was developed for tuning the interface between
nanocrystalline NiO and double cation CsCH3(NH2)2PbI3-xClx absorber in p-i-n
device architectures. We present a unique comprehensive confinement study of
PSCs with TPATC as the self-assembled HTM, including analysis of numerical
defect parameters, phase composition evolution, and up-scaling capabilities.
Our investigation shows that the ultrathin TPATC interlayer effectively
passivates traps, increases work-function of HTL by about ~0.2 eV, and enhances
the charge carrier extraction efficiency. Advanced transient spectroscopy
measurements revealed that modification of the NiO surface with TPATC in
perovskite solar cells (PSCs) reduces the concentration of ionic defects by an
order of magnitude. Interface engineering with TPATC allowed to reach power
conversion efficiency of 20.58% for small area devices (0.15 cm2) under
standard AM 1.5 G conditions. Using TPATC interlayer also provided stabilized
performance of PSCs under operation conditions and improved sustainability of
the perovskite absorber to decomposition. After continuous light-soaking (1000
h, ISOS-L-2 protocol), NiO/TPATC devices showed a slight decrease of 2% in
maximum power. In contrast, NiO PSCs demonstrated decrease in power output
(>20%) after 400 h. We explored the potential of TPATC to modify interfaces in
large-area perovskite solar modules (PSM, active area-64.8 cm2, 12 sub-cells).
By applying slot-die-coated TPATC, the PCE at AM 1.5 G conditions increased
from 13.22% for NiO PSM to 15.64% for NiO/TPATC ones. This study provides new
insights into the interface engineering for p-i-n perovskite solar cells,
behavior of the ionic defects and their contribution to the long-term
stability.
