Elucidating the improved properties of defect engineered lanthanum-doped nickel oxide as hole-transport layer in triple-cation perovskite solar cells

Charge recombination at the interface between the hole transport layer (HTL) and perovskite (PVK) has been a performance bottleneck for perovskite solar cells (PSCs). We present a detailed examination for the solar cell efficiency of the device using lanthanum (La)-doped nickel oxide (NiOx) as an HTL. The NiOx and La-doped NiOx films were prepared using the spray pyrolysis process. We employed low-temperature photoluminescence (LT-PL) to estimate the defect activation energy and utilized SCAPS 1D software to simulate the interface defect density. According to the data obtained, the interface between La:NiOx and PVK shows a lower activation energy for defects, indicating that it is more advantageous for charge transfer compared to the interface between NiOx and PVK. Utilizing SCAPS simulations the experimental JV curves closely match the simulated JV curves obtained from SCAPS simulations. These simulations were performed using optimal parameters, obtained by increasing the R-sh values and reducing the interface density in La:NiOx based PSCs. The interface defect densities are estimated to be La:NiOx/PVK and NiOx/PVK interfaces are 1 x 10(12) cm(-2) and 1.7 x 10(12) cm(-2), respectively. This indicates approximate to 70 % reduction in defect density at the La:NiOx/PVK interface compared to the NiOx/PVK interface. The conductivity values obtained from linear sweep voltammetry (LSV) are 1.01 x 10(-3) S cm(-1) for NiOx films and 1.21 x 10(-3) S cm(-1) for La:NiOx films. This indicates a significant enhancement of approximate to 20 % in the conductivity of La:NiOx films compared to undoped films. This leads to improvements in V-OC and ultimately enhances the PCE. The calculating defect density at the HTL/PVK interface can contribute to the fabrication of futuristic highly efficient PSCs.