Nickel oxide (NiOx) is one of the most widely employed hole transport layers (HTLs) in inverted perovskite solar cells (PSCs) due to its low-temperature processability, compatibility with scalable fabrication, and favorable energy-level alignment. Since 2015, extensive efforts have been devoted to enhancing the optoelectronic properties of NiOx; however, most studies have predominantly focused on planar NiOx (pNiOx) films. In this study, we fabricate a mesoporous nickel oxide (mNiOx) HTL via high-temperature calcination, using nickel nitrate hexahydrate (Ni(NO3)2·6H2O) as the nickel precursor, Pluronic P123 and a small amount of polyvinylpyrrolidone (PVP) as structure-directing templates. The resulting mesoporous framework modulates the perovskite crystallization kinetics, enhances the buried interface, improves the crystallization quality, reduces the defect density, and shifts the interfacial stress state from tensile to compressive. Consequently, both the open-circuit voltage (VOC) and fill factor (FF) of the devices are significantly enhanced. The PSCs based on the mNiOx HTL achieve a power conversion efficiency (PCE) of 23.19%, along with markedly improved operation and storage stability.
In this work, we systematically investigate the lattice thermal conductivity (κL) of LaMoN3 in the C2/c and R3c phases using first-principles calculations combined with the Boltzmann transport equation. In the C2/c phase, κL exhibits strong anisotropy, with values of 0.75 W/mK, 1.89 W/mK, and 0.82 W/mK along the a, b, and c axes, respectively, at 300 K. In contrast, the R3c phase shows nearly isotropic thermal conductivity, with values of 6.28 W/mK, 7.05 W/mK, and 7.31 W/mK along the a, b, and c directions. In both phases, acoustic and low-frequency optical phonons dominate the thermal transport. However, the C2/c phase exhibits increased three-phonon scattering leading to smaller values of κL. Additionally, four-phonon scattering plays a dominant role in the C2/c phase, reducing κL by approximately 96%, whereas in the R3c phase, it leads to a smaller but still significant reduction of ∼50%. These results highlight the critical role of four-phonon interactions in determining the thermal transport properties of LaMoN3 and reveal the stark contrast in thermal conductivity between its two structural phases.

