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Realizing the theoretical limiting power conversion efficiency (PCE) in perovskite solar cells requires a better understanding and control over the fundamental loss processes occurring in the bulk of the perovskite layer and at the internal semiconductor interfaces in devices. One of the main challenges is to eliminate the presence of charge recombination centres throughout the film which have been observed to be most densely located at regions near the grain boundaries. Here, we introduce aluminium acetylacetonate to the perovskite precursor solution, which improves the crystal quality by reducing the microstrain in the polycrystalline film. At the same time, we achieve a reduction in the non-radiative recombination rate, a remarkable improvement in the photoluminescence quantum efficiency (PLQE) and a reduction in the electronic disorder deduced from an Urbach energy of only 12.6 meV in complete devices. As a result, we demonstrate a PCE of 19.1% with negligible hysteresis in planar heterojunction solar cells comprising all organic p and n-type charge collection layers. Our work shows that an additional level of control of perovskite thin film quality is possible via impurity cation doping, and further demonstrates the continuing importance of improving the electronic quality of the perovskite absorber and the nature of the heterojunctions to further improve the solar cell performance.

Boron is used as a grain boundary strengthener in the nickel-based superalloys, but the reasons for its effect and the optimum quantities which need to be added are not well understood. Recently, some of the authors have developed a new corrosion-resistant single crystal superalloy for power generation applications which has a good balance of mechanical properties and resistance to environmental degradation. Here, this same alloy system is studied but in the polycrystalline state with additions of boron and carbon. The influence of boron on creep behaviour has been quantified and rationalised, with an emphasis on the grain boundary phase transformations which occur. NanoSIMS is utilised to investigate the segregation of boron at grain boundaries, with SEM used to characterise the effect of boron on the precipitation of Cr 23C6type carbides at grain boundaries. When the boron content increases, the agglomeration of M23C6carbides at grain boundaries is inhibited. Uniformly distributed discrete M 23C6carbides are observed at higher boron content, whereas a deleterious film of M23C6along the grain boundaries arises as the boron concentration is reduced. Boron promotes also the formation of γ′ layers at the grain boundaries. © 2014 Owned by the authors, published by EDP Sciences.

In this work, a further study on boronizing using compression method called superplastic boronizing (SPB) was conducted. This process was conducted on duplex stainless steel (DSS) that exhibited superplasticity. Efforts were being put in obtaining ultra hard surface through SPB by focusing on the boron powder particle size. The microstructure, hardness, and layer thickness of the boronized materials were investigated. Comparison using as-received DSS with coarse microstructure also was performed. The overall results from the study showed that the SPB process can produced a very hard surface of close to 4000 HV and significantly improved the surface properties of the DSS.