Perovskite

The application of luminescent down shifting (LDS) layers as alternative UV filters for CH 3 NH 3 PbI 3(1-x) Cl 3x perovskite solar cell (PSC) devices is reported. A combination of photo-absorption measurements and of device decay measurements during light soaking are used to verify the stability. The application of a UV filter or LDS layer was able to significantly retard photo-induced degradation with ~18% drop in device power conversion efficiency (PCE) observed over 30 h for non-encapsulated devices, which is compared to ~97% for an un-filtered device, also without encapsulation. Whilst the PCE of the PSC device decreases with the application of the LDS layer, the drop is not as significant as when a commercial UV filter is used. Considering that UV filters will be essential for the commercialization of PSCs, the work provides evidence that the LDS layer can act as an alternative UV filter in PSCs and can limit the drop in PCE that can be expected from the inclusion of a UV filter, thus providing an added benefit over commercial UV filters.

In the last few years, organic-inorganic halide perovskites (OIHP) have gained significant attention in the optoelectronics community and become one of the most popular research topics. Due to their fascinating properties, including wide-range tunable band gap, long charge carrier diffusion length, high absorption coefficient, and easy solution processability, they have become one of the most promising classes of low-cost and easily scalable semiconductor materials for application in various optoelectronic devices such as solar cells, photodetectors, and light-emitting diodes. To achieve the best performance and viable technologies for future energy harvesting, display and light sensing prototypes, in addition to the OHIP active layer, the use of interfacial charge transporting layers is crucial. These interfacial charge-transporting layers not only enhance the performance of optoelectronic devices but also effectively protect the active environmentally unstable OHIP layer. In this review, we summarize the development and utilization of organic interfacial materials and OIHP in solar cells, photodetectors and light-emitting diodes. In each section, the working principle and the development of a wide range of hole/electron transporting materials are discussed. Finally, an outlook and further research directions as well as useful rules for the design of novel hole/electron transporting materials are proposed. Broader context Organic-inorganic halide perovskite (OIHP)-based optoelectronic devices, which include solar cells, light-emitting diodes, and photodetectors are expected to play an extremely important role in future flexible and printed electronics and can create new applications in the near future. OIHP is one of the most promising classes of low-cost and easily scalable semiconducting active materials, which can be used in various electronic devices. OHIP exhibit outstanding properties including long charge carrier diffusion length, high absorption coefficient, wide-range tunable band gap, and easy solution processability. To harness the OHIP technology for use in devices, there is a great need for interfacial charge transporting layers since they not only boost the performance but also protect the unstable OIHP active layer from degrading in the working environment. In this review, we discuss the molecular and device engineering, optoelectronic properties, and recent research progress in the design of organic interfacial materials for use with OIHP materials in light harvesting, light detection, and display technology.

Nanocrystalline GdAlO 3 À δ powders were prepared by means of solid state-reaction process. The parent compound GdAlO 3 (δ ¼ 0.0) has a broad electronic band gap of 5.0 eV and do not present photolumines-cence (PL) emission. This work aims to study the effect of the introduction of oxygen deficiencies in the GdAlO 3 À δ compounds on the establishing of PL signal. XRD patterns revealed that all samples present an orthorhombic structure with the absence of structural transition when increasing δ. The optical study exposed a very intense green PL emission, observed at room temperature and centered at 530 nm using a 350 nm excitation line. The PL emission was related to the oxygen deficiencies doubly ionized vacancy V O , created in the orthorhombic structure of GdAlO 3 À δ compounds, which may be responsible for the formation of intermediary energy levels into the band gap.

Powders of BaY x Ce 1 − x O 3 − δ (x = 0, 0.1 and 0.15) with specific surface area of 6-8 m 2 g − 1 (BET equivalent particle size of 130-160 nm) were prepared by a modified solid-state route using nanocrystalline BaCO 3 and CeO 2 raw materials. These powders showed excellent densification at relatively low temperatures. Dense (96-97% relative density) ceramics with submicron grain size (0-4-0.6 µm) were obtained after sintering at 1250-1280°C. Ceramics sintered at 1450°C revealed only a moderate grain growth (grain size ≤2 µm), uniform microstructure and very high density (≥98%). The total conductivity of the submicron ceramics at 600°C was comparable with the reference values reported in the literature, meaning that the high number of grain boundaries was not a limiting factor. On lowering temperature, the contribution of the blocking grain boundaries becomes progressively more important and the conductivity decreases in comparison to coarse-grained ceramics. Microscopic conductivities of grain interior and grain boundary are the same irrespective of grain size meaning that the different macroscopic behaviour is only determined by a geometric factor (a trivial size effect).