University of Toronto researchers create a more stable electron selective layer for PSCs and tandem solar cells

Researchers at the University of Toronto have designed a method of growing a more stable electron selective layer for perovskite solar cells and tandem solar cells combining crystalline silicon with perovskite.

University of Toronto researchers make Quantum Dots and Perovskite Solar Cells at 150°C image

Perovskite raw materials can be mixed into a liquid in a kind of ‘solar ink.’ This solar ink could be printed onto glass, plastic or other materials with a relatively simple inkjet printing process. However, in order to generate electricity, electrons excited by solar energy from perovskite cells must be extracted from a layer of quantum dots that is held together by a passivation layer. Some types of quantum dots are known to change their 3D structure even at room temperature, making them transparent and ineffective. This passivation layer is also known to break down at temperatures above 100°C. The team’s breakthrough made both quantum dots and perovskites more stable when combined than they are separated and the solar cell combining of Perovskite material and quantum dots achieved 20.1% efficiency.

NREL team boost PSC efficiency using a new chemical formula

Researchers at the National Renewable Energy Laboratory (NREL) report the creation of an efficient tandem perovskite solar cell, using a new chemical formula which also improved the structural and optoelectronic properties of the solar cell.

Most of the research efforts in the field of PSCs have focused on lead-based perovskites, which have a wide bandgap. High efficiency, low bandgap perovskites would enable the fabrication of very high efficiency all-perovskite tandem solar cells where each layer absorbs only a part of the solar spectrum and is optimally configured to convert this light into electrical energy. However, low bandgap perovskites have long suffered from large energy losses and instability limiting their use in tandems.

Netherlands’ ECN reaches 30.2% efficiency for bifacial tandem cell based on perovskite

Researchers at the Energy Research Center of the Netherlands (ECN) have developed a bifacial tandem solar cell with a conversion efficiency of 30.2%. The new cell device – created with Dutch consortium Solliance – was made by applying a newly developed perovskite cell on top of an industrial bifacial crystalline silicon version.

Netherlands’ ECN reaches 30.2% efficiency for bifacial tandem cell based on perovskite

This approach, according to the scientists, enables a significantly higher power conversion efficiency as one cell is optimized for high energy photons, and the other low energy particles. “The tandem device proposed here uses a four-terminal configuration, thus having separate circuits for the top and bottom cells that allow for dynamic fine tuning and optimization of the energy yield,” the creators of the cell wrote. The cell is also said to be better able to capture light on its front and rear sides by responding to the variability of incident light through its electronic design.

Researchers reduce reflection losses and reach 25.2% conversion efficiency in perovskite/silicon tandem solar cells

Researchers from HZB, Oxford University, Technical University Berlin and Oxford PV have shown that the infrared reflection losses in tandem cells processed on a flat silicon substrate (such as perovskite/silicon tandem cells) can be significantly reduced by using an optical interlayer, consisting of nanocrystalline silicon oxide. Based on this, the team managed to achieve impressive efficiency and reported that the best tandem device in this work reached a certified conversion efficiency of 25.2%.

Researchers at HZB and Oxford reduce reflection losses and reach 25.2% conversion efficiency in perovskte/silicon tandem solar cells imagea) Cross-section of the simulated monolithic perovskite/SHJ tandem cell (layer thicknesses and morphological features not to scale). b) Cross-sectional SEM image of the top region of the tandem device.

Perovskite/silicon tandem solar cells are attractive for their potential for boosting cell efficiency beyond the crystalline silicon (Si) single-junction limit. However, the relatively large optical refractive index of Si, in comparison to that of transparent conducting oxides and perovskite absorber layers, often results in significant reflection losses at the internal junction between the cells in monolithic (two-terminal) devices. Therefore, light management is crucial for improving photocurrent absorption in the Si bottom cell.

HZB team achieves 21.6% efficiency for perovskite CIGS tandem solar cell

Researchers at the Germany-based Helmholtz Center Berlin (HZB) have announced a thin-film solar cell made of perovskite and copper-indium-gallium-selenide (CIGS) with an efficiency of 21.6%.

The HZB researchers said they used a simple, robust production process suitable for scaling up. Rutger Schlatmann, director of the HZB’s Institute PVcomB, spoke of an “enormous step in the direction of commercial production”. The HZB team’s tandem cell could theoretically reach an efficiency of more than 30%, according to the researchers.