Inorganic Ruddlesden-Popper Faults in Cesium Lead Bromide Perovskite Nanocrystals for Enhanced Optoelectronic Performance

Structure and Charge Carrier Separation Promotion Effects of Antiphase Boundaries in Cesium Lead Bromide

Defects in lead halide perovskites (LHPs) may have a significant impact on charge carrier separation, but the roles of the defects are not fully understood. Here, using aberration-corrected scanning transmission electron microscopy (STEM), different types of antiphase boundaries (APBs) are discovered in CsPbBr3 platelets. APBs with a displacement vector of 1/4[111] are characterized by double layers of CsBr layers at the (110) or (001) planes, while APBs at the (112) planes are formed through edge sharing of PbBr6 ̵octahedra. Significant lattice distortions are determined at (001) and (110) APBs on the basis of quantitative analyses of STEM images. Density functional theory calculations demonstrate that all three types of APBs can induce band offsets at their valence bands and conduction bands. The APBs are intended to promote the separation of photogenerated charge carriers in LHPs. These findings provide a crystal engineering technique for enhancing the optoelectronic properties of LHPs by controlling defects.

First-principles predictions of enhanced thermoelectric properties for Cs2SnI2Cl2and Cs2PbI2Cl2monolayers with spin-orbit coupling

Inspired by the exceptional charge transport properties and ultra-low thermal conductivity of halide perovskite, we investigate the electronic nature, thermal transport, and thermoelectric properties for Ruddlesden-Popper all-inorganic perovskite, Cs2SnI2Cl2and Cs2PbI2Cl2monolayers, using first-principles calculations. During the calculations, spin-orbit coupling has been considered for electronic transport as well as thermoelectric properties. The results show that the Cs2SnI2Cl2and Cs2PbI2Cl2monolayers exhibit high carrier mobility and low thermal conductivity. Stronger phonon-phonon interaction is responsible for the fact that thermal conductivity of Cs2SnI2Cl2monolayer is much lower than that of Cs2PbI2Cl2monolayer. At 700 K, the values of the figure of merit (ZT) for the n-type doped Cs2SnI2Cl2and Cs2PbI2Cl2monolayers are about 1.05 and 0.32 at the optimized carrier concentrations 5.42 × 1012cm-2and 9.84 × 1012cm-2. Moreover, when spin-orbit coupling is considered, the correspondingZTvalues are enhanced to 2.73 and 1.98 at 5.27 × 1011cm-2and 6.16 × 1011cm-2. These results signify that Cs2SnI2Cl2and Cs2PbI2Cl2monolayers are promising thermoelectric candidates.