Efficiency - Page 63

Scientists at the U.S. Department of Energy's (DOE) National Renewable Energy Laboratory (NREL), in collaboration with researchers at Shanghai Jiao Tong University (SJTU), have reportedly devised a method to improve perovskite-based solar cells, making them more efficient and reliable with higher reproducibility.

The research was funded by the DOE's SunShot Initiative. It involved hybrid halide perovskite solar cells and revealed treating them with a specific solution of methyl ammonium bromide (MABr) would repair defects, improving efficiency. The scientists converted a low-quality perovskite film with pinholes and small grains into a high-quality film without pinholes and with large grains. This apparently boosted the efficiency of the perovskite film in converting sunlight to 19%, according to NREL.

A research group at the Japan-based National Institute for Materials Science (NIMS) reported the achievement of energy conversion efficiency exceeding 18% using standard size (1 cm2) perovskite solar cells. This measurement was made by the Calibration, Standards and Measurement Team at the Research Center for Photovoltaics, National Institute of Advanced Industrial Science and Technology (AIST)'an internationally recognized independent organization for solar cell evaluation.

The research group developed high-quality crystal particles that constitute a perovskite layer by adjusting the ratio of different cations in the layer and by substituting some of the iodine with bromine. Consequently, they were able to efficiently extract electrons and holes formed by exposure to light, and succeeded in increasing the short-circuit current density to more than 21 mA/cm2. Furthermore, they accurately controlled the thickness of layers in solar cells such as perovskite and electron transport layers and thereby reduced electrical resistance within the solar cells. As a result, they were able to reach this increased conversion efficiency of 18.2%.

Researchers from Los Alamos National Laboratory, Rice University and Northwestern University have been working on modifying perovskites' manufacturing technique and producing a new variety of 2D layered perovskite with exceptional strength and increased power transformation capability.

Three types of large-area solar cells made out of two-dimensional perovskites. At left, a room-temperature cast film; upper middle is a sample with the problematic band gap, and at right is the hot-cast sample with the best energy performance.

Using a spin-casting technique, the team managed to create layered crystals whose electrons flow vertically down the material without being blocked, midlayer, by organic cations. The researchers stated that 'the new 2D perovskite is both more efficient and more stable, both under constant lighting and in exposure to the air, than the existing 3D organic-inorganic crystals'.

Researchers at the U.S. Department of Energy's Lawrence Berkeley National Laboratory have found that it may be possible to boost energy conversion rates perovskite-based solar modules by as much as 40%.

Using an atomic microscope, the researchers observed multifaceted surfaces in perovskite solar cells. Some of the grains, which were about 200 microns in width, had sharply formed multi-angled facets, while others were poorly formed. The poorly formed facets had energy conversion efficiencies approaching 31%, which beats today's most optimistic photovoltaic efficiency rates of around 22%.

Researchers at the University of Washington, the Massachusetts Institute of Technology and the University of Oxford have been trying to find ways to repair inherent perovskite defects in order to improve the efficiency of solar cells. They showed that the photons they shined on the perovskite cells had a therapeutic effect, and exposure to intense visible light increased the energy conversion efficiency of the perovskite crystals.

Using perovskite crystals synthesized at Oxford University, the scientists showed that intense light exposure helped crystals repair themselves by physically transporting iodine during illumination. They used two powerful imaging techniques to show that iodine ions within perovskite crystals moved away from intense light.

Nanoelectronics research center imec has presented what is thought to be the first-ever semi-transparent perovskite PV-module, achieving power conversion efficiencies up to 12%. This technology may enable semi-transparent PV-windows and other such advanced applications. Moreover, combining these semitransparent perovskite modules with Si solar cells, an unprecedented 20.2% in power conversion efficiency for a perovskite/Si stacked solar module was achieved.

The semi-transparent perovskite modules of imec realized by scalable coating techniques showed efficiencies of 12% on sizes as large as 4 cm2 and 10 % on sizes as large as 16cm2, a world-best achievement in this domain.

A team of scientists from Israel, Singapore, and Switzerland has reported a major advance in the physics of perovskite solar cells ' by producing high-performance cells whose efficiency surprisingly improved as the cells heated up, in contrary to the usual drop in efficiency that occurs upon heating of a solar cell.

The researchers used experiments that varied the intensity of light and cell temperature, helping to better understand the molecular mechanisms that allow these solar cells to discharge high voltage while maintaining high current density and low internal resistance, which are essential for their superior performance. The study suggests deploying perovskite solar cells under concentrated sunlight in order to realize even higher efficiency'one of the next tasks in their planned experimental studies.

Solliance announced a 10% aperture area power conversion efficiency for its up-scaled thin-film perovskite photovoltaic modules. The efficiency was measured on an aperture area of 168 cm². Twenty-five cells were serial connected through an optimized P1, P2, P3 interconnection technology. The PV module was realized on a 6x6 inch glass substrate using industrial scale-able slot die coating in combination with laser patterning.

Based on previous optimization on 16 cm² modules, the Solliance team was able to transfer this to a 6x6 inch sized glass substrate using the developed blade coating process and the optimized mechanical patterning technology. These results demonstrate the up-scalability of this new thin film PV technology. Apart from the electrodes currently used, all layers can be processed in ambient environment and at temperatures below 120⁰C. Furthermore, the deposition and interconnection technologies used for obtaining these results are industrially available for Sheet-to-Sheet as well as for Roll-to-Roll manufacturing. The latter allows for creating high volume production in the future.

Researchers at the Department of Energy's Oak Ridge National Laboratory (ORNL) have found a potential way to further improve solar cell efficiency by understanding the competition among halogen atoms during the synthesis of sunlight-absorbing crystals.

Using high-powered imaging techniques, the team tracked kinetic activity in organometallic halide perovskites. Halogen ions, competing for a position in the growing structure, affect the movement of charges through the crystals and subsequently impact the efficiency of sunlight's conversion to electricity.

A recent market report by Lux Research stated that perovskites offer several new opportunities for partnerships with universities ahead of a likely commercial deployment between 2019 and 2021. While efficiency of perovskite-based solar cells is constantly improving, the main remaining issues are stability, cost, and the feasibility of real-world efficiencies that must be addressed before commercialization can occur.

Lux Research analysts evaluated the existing state of perovskite solar cells and identified opportunities for companies to partner with academia. Among their findings are the following: partnerships are continuously emerging from labs, and opportunities are still available. Many leading researchers have clear partnerships, but opportunities are still present with various institutions and universities. Also, China is the leading publisher on perovskite solar cells, accounting for a quarter of all academic publications, but more impactful research is coming out of Israel, Switzerland, Singapore, and the UK. China is followed by the USA and South Korea. However, European countries ' the UK, Italy, Switzerland, Germany, Spain, Sweden, France, Greece and Belgium - together account for 24% (almost equivalent to China).