Novel Energy Materials and Advanced Characterisation

Abstract:

The notion of periodicity in crystals is examined and how this can be varied in practice. In particular, the article discusses first of all the concept of superstructures, in which some sort of alternating motif occurs thus changing the repeat distance in a lattice. Crystals of this type are often incorrectly called in the literature superlattices: first of all they cannot be called lattices at all as they consist of atoms (a lattice must only consist of points). In any case such a superstructure is formed from a sublattice rather than a superlattice. In addition, some crystals do not have normal periodicity within a three-dimensional space, and are known as aperiodic crystals. Despite being aperiodic, they are still ordered. In mathematical terms they can by described with respect to a higher-dimension space and then projected back onto three dimensions. This generalizes our notion of what is meant by a crystal.

Abstract:

Metal halide perovskite semiconductors have shown significant potential for use in photovoltaic (PV) devices. While fabrication of perovskite thin films can be achieved through a variety of techniques, thermal vapor deposition is particularly promising, allowing for high-throughput fabrication. However, the ability to control the nucleation and growth of these materials, particularly at the charge-transport layer/perovskite interface, is critical to unlocking the full potential of vapor-deposited perovskite PV. In this study, we explore the use of a templating layer to control the growth of coevaporated perovskite films and find that such templating leads to highly oriented films with identical morphology, crystal structure, and optoelectronic properties independent of the underlying layers. Solar cells incorporating templated FA0.9Cs0.1PbI3–xClx show marked improvements with steady-state power conversion efficiency over 19.8%. Our findings provide a straightforward and reproducible method of controlling the charge-transport layer/coevaporated perovskite interface, further clearing the path toward large-scale fabrication of efficient PV devices.