Ultrathin TiN Epitaxial Films as Transparent Conductive Electrodes.

Titanium nitride (TiN), a transition-metal compound with tight covalent Ti-N bonding, has a high melting temperature and superior mechanical and chemical stabilities compared to noble metals. With a reduction in thickness, the optical transmittance of TiN films can be drastically increased, and in combination with its excellent electrical conductivity, the ultrathin and continuous TiN film can be considered as an ideal alternative of the metal oxide electrodes. However, the deposition of ultrathin and continuous metallic layer with a smooth surface morphology is a major challenge for typical deposition methods such as thermal evaporation or reactive sputtering.

Terahertz Analysis of CHNHPbI Perovskites Associated with Graphene and Silver Nanowire Electrodes.

In order to investigate the thermal and chemical (in)stabilities of MAPbI incorporated with graphene and silver nanowire (AgNW) electrodes, we employed the terahertz (THz) time-domain spectroscopy, which has a unique ability to deliver the information of electrical properties and the intermolecular bonding and crystalline nature of materials. In in situ THz spectroscopy of MAPbI, we observed a slight blue-shift in frequency of the 2 THz phonon mode as temperatures increase across the tetragonal-cubic structural phase transition. For MAPbI with the graphene top electrode, no noticeable frequency shift is observed until the temperature reaches the maximum operating temperature of solar cells (85 °C).