Progress in hole-transporting materials for perovskite solar cells

In recent years the photovoltaic community has witnessed the unprecedented development of perovskite solar cells（PSCs） as they have taken the lead in emergent photovoltaic technologies. The power conversion efficiency of this new class of solar cells has been increased to a point where they are beginning to compete with more established technologies. Although PSCs have evolved a variety of structures, the use of hole-transporting materials（HTMs） remains indispensable. Here, an overview of the various types of available HTMs is presented. This includes organic and inorganic HTMs and is presented alongside recent progress in associated aspects of PSCs, including device architectures and fabrication techniques to produce high-quality perovskite films. The structure, electrochemistry, and physical properties of a variety of HTMs are discussed, highlighting considerations for those designing new HTMs. Finally, an outlook is presented to provide more concrete direction for the development and optimization of HTMs for highefficiency PSCs.

How to get high-efficiency lead chalcogenide quantum dot solar cells?

Lead chalcogenide colloidal quantum dots(CQDs)are regarded as attractive absorption materials for novel solar cells(SCs).The cost of lead chalcogenide CQD has been decreased to a commercialization target of$5/g due to the direct production of CQD inks.However,the photoelectric conversion efficiency(PCE)of lead chalcogenide CQDSCs is presently close to 14%,well below the commercialization target(20%),which is only 41%of the theoretical Shockley-Queisser limit efficiency.In this study,the different losses of open-circuit voltage(V_(oc)),fill factor(FF),and short circuit current density(J_(sc))for current CQDSCs are systematically discussed,as well as the percentage and likely causes of each loss.Then the primary reasons for the CQDSCs’performance constraints are highlighted.Following that,we focus on the CQDSCs interfaces(i.e.,CQD/CQD,CQD/HTL,and ETL/CQD)and explore viable ways to reduce device performance loss.Finally,based on the discussion above,we propose many enhancements to significantly solve numerous major obstacles impeding device performance to boost the PCE of CQDSCs for future commercialization significantly.

A simulation study of airborne wear particles from laboratory wheel-rail contacts

Laboratory measurements of airborne particles from sliding contacts are often performed using a tri- bometer located in a ventilation chamber. Although knowledge of particle transport behavior inside the chamber is required because it can influence the analysis of measurements, this knowledge is lacking. A numerical model was built based on the same geometry as a pin-on-disc measurement system to explain particle transport behavior inside the chamber and to determine the deviation between real amounts of generated and measured particles at the outlet. The effect of controlled flow conditions on the airflow pattern and particle transport inside the chamber was studied for different experimental conditions. Cal- culations show that a complex airflow pattern is formed by the spinning disc, and that it differs for each rotational speed. Simulation results reveal that particle transport in the chamber is governed mainly by the airflow pattern. The deposition velocity in the chamber was estimated and the possibility that part of the generated particles would remain in the chamber was studied. This led to an approximate estima- tion of particle loss rate. A comparison between experimental and simulated results with respect to the particle mass flow rate close to the outlet yields a reference factor of 0.7, which provides an indication of the difference between measured and real values.