Efficiency - Page 42

The EPFL launched a new project, supported by the Valais State Government with 5 million Swiss Francs, to realize a "demonstrator project" at EPFL-Sion Campus Energypolis.

Sized at the canton or district level, these installations will enable the testing of technologies developed in the laboratories of EPFL Valais-Wallis in real conditions, with the collaboration of local partners and the HES-SO Valais-Wallis.

A Florida State University research team has addressed perovskite solar cells' stability issue by mixing the old with the new. Professor of Chemistry Biwu Ma and his team published a new study that shows if you add a layer of ancient organic pigment to a perovskite solar cell, it increases the stability and efficiency of the cell.

'Pigments are abundant, low cost and robust,' Ma said. 'When we combine them with perovskites, we can generate new high-performance hybrid systems. It's using the old with the new, and together they produce something really exciting.'

Researchers at POSTECH recently developed an organic spacer molecular additive that can improve both the photoelectric efficiency and stability of perovskites.

The POSTECH team, led by Professor Kilwon Cho and Ph.D. candidate Sungwon Song of the Department of Chemical Engineering, succeeded in fabricating perovskite solar cells that are highly efficient and stable by drastically reducing the concentration of internal defects in the crystals as well as increasing the moisture resistance of perovskite by introducing a new organic spacer molecule additive in the perovskite crystal.

A research team at Stanford University has designed a new perovskite manufacturing process. In their work, the team demonstrated an ultrafast way to produce stable perovskite cells and assemble them into solar modules that could power devices, buildings and even the electricity grid.

'This work provides a new milestone for perovskite manufacturing,' said study senior author Reinhold Dauskardt, the Ruth G. and William K. Bowes Professor in the Stanford School of Engineering. 'It resolves some of the most formidable barriers to module-scale manufacturing that the community has been dealing with for years.'

Organic-inorganic hybrid perovskites (OIHPs) have great potential for various applications like solar cells, lighting-emitting diodes (LEDs), field effect transistors (FETs) and photodetectors. Among their most important parameters influencing the power conversion efficiency (PCE) of devices based on perovskite materials is their carrier mobility. However, despite massive progress made by introducing new components into the structure to control the mobility of the carriers, the understanding on the atom level of how the components affect the performance is still lacking.

To address this problem, a research team led by Prof. Luo Yi and Prof. Ye Shuji from the University of Science and Technology of China (USTC) of the Chinese Academy of Sciences (CAS) has synthesized a series of 2D OHIPs films with large organic spacer cations.

Researchers from South Korea's Ulsan National Institute of Science and Technology (UNIST) have reported a conversion efficiency of 25.17% in a perovskite solar cell, achieved by minimizing the deformation for the microstructure of photoactive layers in the device.

The inner structure of the newly-developed photoactive layer, as well as the working principle of the perovskite cell. Image: Unist

The team explained that the microstructure of these layers, which generate an electric charge and send it to electrodes, can be deformed - which affects the efficiency of the charge transfer itself. 'This is because the extracted electric charges disappear when defects are formed,' they explained.

KAUST researchers have developed a perovskite ink tailor-made for a mass manufacturing process called slot-die coating, producing PSCs that captured solar energy with high efficiency. The ink could also be coated onto silicon to create perovskite/silicon tandem solar cells.

The planar p-i-n device architecture of the perovskite solar cell employed in the study. Image credit: KAUST

PSCs made in research labs are typically made by spin-coating, which is unsuited to mass manufacture. Slot-die coating, in contrast, is a manufacturing technique used industrially for many years. 'The process involves continuously and precisely forcing an ink through a narrow slit that is moved across the substrate to form a continuous film,' Anand Subbiah, a postdoc in Stefaan De Wolf's lab, said. 'This high-throughput technique would allow for roll-to-roll fabrication, similar to printing newspapers.'

KAUST researchers have conducted outdoor tests, that have shown that an increase in temperature affects the performance of a tandem perovskite/silicon solar cell due to voltage losses aw well as current mismatch between the two sub-cells.

The energy yield of two-terminal tandem cells is maximized when the two sub-cells produce the same current at the maximum power point. However, when one of the two devices generates less current than the other, and current mismatch between the sub-cells occurs, the overall device's current is affected.

Researchers from Singapore's Nanyang Technological University have developed a mini solar module based on thermally evaporated perovskites with an efficiency of 18.4% and a geometric fill factor (GFF) of around 91%. The team believes that the panel could be a real step forward in the industrialization of perovskite mini-modules.

The panel has an active area of 6.4 cm² and is based on co-evaporated methylammonium lead iodide (MAPbI₃). The thickness of the MAPbI₃ films was 750 nm, and the films were used to create solar cells with an 'n-i-p' layout on fluorine-doped tin oxide (FTO) glass substrates.

Researchers led by Eindhoven University of Technology in the Netherlands have developed a process that allowed them to fabricate three perovskite layers, and combined these layers into a device that reached 16.8% conversion efficiency.

While tandem cells are the focus of intensive research, combining several active layers into one cell is less explored. Efficiencies close to the 40% mark have been achieved with III-V materials, but for all perovskite devices, the efficiency record previously stood at 6.7%.