Interfaces between Pb-Free Double Perovskite Cs 2 NaBiI 6 and MXenes Sc 2 CO 2 and Sc 2 C(OH) 2

First-principles calculations are used to explore the electronic properties of the interfaces between the Pb-free double perovskite Cs NaBiI and the MXenes Sc CO and Sc C(OH) . The effect of the termination group on the stability, ionization potential, electron affinity, and band alignment is investigated. We find a type II band alignment at the Cs NaBiI /Sc CO interface, which permits charge transfer, and a type III band alignment at the Cs NaBiI /Sc C(OH) interface, which results in electron-hole recombination. Sc CO turns out to be highly promising for solar cell applications due to an almost ideal ionization potential difference to Cs NaBiI .