September 2019

MIT researchers have designed perovskite photovoltaic-powered sensors that could potentially transmit data for years before they need to be replaced. To this end, the team mounted thin-film perovskite cells as energy-harvesters on inexpensive radio-frequency identification (RFID) tags.

The cells could power the sensors in both bright sunlight and dimmer indoor conditions. Moreover, the team found the solar power actually gives the sensors a major power boost that enables greater data-transmission distances and the ability to integrate multiple sensors onto a single RFID tag.

Researchers at the University of Rome Tor Vergata in Italy and Russia's NUST MISIS institute have investigated how cells containing two-dimensional titanium-carbide MXene support layers could improve perovskite solar cell performance.

To obtain good power conversion within a perovskite solar cell, all layers and layer interfaces within the cell must have good compatibility. Typical cells contain the active perovskite material sandwiched between two charge transport layers, which are then adjacent to their corresponding electrodes. Support layers may also be added. Charge mobility, energy barriers, interface energy alignment, and interfacial vacancies all impact compatibility and subsequent cell performance and stability. Thus, engineering well-suited interfaces with the cell is paramount to cell success and long-term stability, an important criterion for potential commercialization.

Researchers at UC Merced, Professors Sayantani Ghosh and David Strubbe and their students in the Department of Physics, have been working on a NASA initiative to fabricate solar cells in space and turn sunlight into electricity. 'One of the big challenges with solar cells is that they are heavy, and NASA has been building them on Earth and then taking them into space,' Ghosh said.

Ghosh and her lab work with perovskites - they developed a simple, efficient process for creating perovskite solar films called 'electrospraying.' The method does not require gravity because it creates its own electric field and creates extremely smooth solar-energy-absorbing films. Now the researchers want to see if NASA can put it to use.

Researchers at the Weizmann Institute of Science have found that in halide perovskites, creating defects takes more effort than restoring order. This finding may explain the remarkable properties of halide perovskites and help develop a new approach to controlling the properties of these and other materials.

Much about Halide perovskites still puzzles researchers; in particular, it has been unclear why they can contain relatively few defects, on the order of 1010 per cubic centimeter (that is, one defect for every trillion atoms, instead of the one to a hundred for every million, as in regular semiconductors). This concentration of defects rivals that of germanium crystals, among the cleanest solid-state man-made materials. Getting close to such a low defect concentration in the semiconductors used in today's electronic devices requires enormous effort and ingenuity. In contrast, halide perovskites can be produced within a fraction of a second by mixing simple chemical salt solutions at near room temperature.

Researchers from the Ulsan Institute of Science and Technology (UNIST) have demonstrated a new method of fabricating perovskite-on-silicon tandem devices, using a transparent conductive adhesive (TCA) to combine the two cells. The scientists have developed devices with demonstrated efficiencies of 19.4%, and propose methods to bring that up to over 24% using existing technology.

While the efficiency is still well below the 28% record for a perovskite/silicon tandem cell set by Oxford PV, the UNIST group says its method is far simpler to manufacture than previous concepts. 'It is meaningful to develop an attached tandem solar cell unlike the conventional tandem solar cell with stacked structure,' said UNIST's In Young Choi, lead author of the study. 'We have observed that the TCA effectively connects the different light-absorbing layers.'

A team led by Prof. Steve Albrecht from the HZB has announced a new world-record: a tandem solar cell with certified efficiency of 23.26% that combines the semiconducting materials perovskite and CIGS. One reason for this success lies in the cell's intermediate layer of organic molecules: they self-organize to cover even rough semiconductor surfaces. Two patents have been filed for these layers.

Perovskite-based solar cells have experienced an incredibly rapid increase in efficiency over the last ten years. The combination of perovskites with classical semiconductor materials such as silicon and copper-indium-gallium-selenide (CIGS) compounds in tandem solar cells promises low-cost, high-performance solar modules for the future. However, losses at the electrodes between the two semiconductors considerably reduce the efficiency.

Solliance and U.S-based MiaSolé announced a new record - power conversion efficiency of 23% on a flexible tandem solar cell: a top flexible semi-transparent perovskite solar cell with a bottom flexible copper indium gallium selenide (CIGS) cell.

This achievement comes only 9 months after the January 2019 announcement by Solliance and MiaSolé regarding a flexible solar cell with an impressive power conversion efficiency of 21.5%. The solar cell, similarly to this newly announced one, combined two thin-film solar cell technologies into a 4 terminal tandem solar cell stack: a top flexible semi-transparent perovskite solar cell with a bottom flexible copper indium gallium selenide (CIGS) cell.

Researchers from the University of Tennessee and Oak Ridge National Laboratory have found that the environment is a non-trivial component in the operation of organometal halide perovskite (OMHP) devices, playing an important role in the charge transport behavior at the electrode/crystal interface of OMHPs due to coupling between surface mediated redox processes and bulk ionic species.

The team explored environmental and interface effects, namely transport behavior and origins of the gas sensitivity, in MAPbBr₃ single crystal (SC) devices using impedance spectroscopy and G-Mode Kelvin Probe Force Microscopy (G-KPFM). Strong resistive response was found to occur when the crystals were exposed to different environments. It was shown, among other things, that SC response to the environment is extremely different at the surface as compared to the bulk due to the disorder surface chemistry.

Several research institutions in South Korea are actively conducting research and development on next-generation solar cells, heightening expectations for commercialization. The research team led by Prof. Yoon Soon-gil of Chungnam National University has developed a new graphene electrode to produce perovskite solar cells at a low temperature. In addition, the team led by Prof. Choi Kyoung-jin of the School of Materials Science and Engineering at UNIST has developed a new concept tandem solar cell using transparent conductive adhesives (TCA).

The graphene electrode developed by Professor Yoon's team can help create a perovskite solar cell at a low temperature and can raise both safety and economic efficiency.

Perovskites have shown potential for use as high performance photodetectors, where the responsivity and detectivity of the perovskite photodetector (PePDs) can be improved by engineering its interfacial properties. Researchers from the University of Electronic Science and Technology of China (UESTC) and City University of Hong Kong have reported the applications of bio-inspired materials, deoxyribonucleic acid (DNA) and guanine, as functional interfacial layers for high performance PePDs.

The best bio-material modified PePDs exhibit a ∼2× enhancement of the photo-current than that of the reference PePDs with no modifications. Further optimization of the thickness for the bio-materials based functional layers enables the PePD to achieve a remarkable responsivity of 0.37 A W'1 and detectivity of 1.85'×'1012 Jones at the wavelength of 745 nm.