Researchers at the Adolphe Merkle Institute in Fribourg and the Ecole Polytechnique Fédérale de Lausanne have developed a new technique to replace one of the least stable components in perovskite solar cells, which could be a major step towards commercialization.

Perovskites are seen as promising thin-film solar-cell materials because they can absorb light over a broad range of solar spectrum wavelengths thanks to their tuneable bandgaps. Charge carriers (electrons and holes) can also diffuse through them quickly and over long lengths. The most efficient perovskite solar cells usually contain bromide and MA, which is thermally unstable. To overcome this problem, researchers tried replace MA with FA since it is not only more thermally stable but also has an optimal redshifted bandgap. Unfortunately, because of its large size, FA does distort the perovskite lattice and tends to produce a photoinactive 'yellow' phase at room temperature. The other photoactive 'black phase' can only be seen at high temperatures. However, the researchers in this new work have now found a way to stabilize the black phase of FA at room temperature.

Researchers at UvA-IoP have shown that certain perovskites possess the desirable property of carrier multiplication ' an effect that makes materials more efficient in converting light into electricity.

Research leaders Dr. Chris de Weerd and Dr. Leyre Gomez explain this property, which had so far not been shown to exist in perovskites. When semiconductors ' in solar cells, for example ' convert the energy of light into electricity, this is usually done one particle at a time: a single infalling photon results in a single excited electron (and the corresponding 'hole' where the electron used to be) that can carry an electrical current. However, in certain materials, if the infalling light is energetic enough, further electron-hole pairs can be excited as a result; it is this process that is known as carrier multiplication.

Researchers at Duke University computationally predicted the electrical and optical properties of layered hybrid organic-inorganic perovskites (or HOIPs) - popular materials for light-based devices such as solar cells and light-emitting diodes (LEDs). The ability to build accurate models of these materials atom-by-atom will allow researchers to explore new material designs for next-generation devices.

'Ideally we would like to be able to manipulate the organic and inorganic components of these types of materials independently and create semiconductors with new, predictable properties,' said David Mitzi, Professor of Mechanical Engineering and Materials Science at Duke. 'This study shows that we are able to match and explain the experimental properties of these materials through complex supercomputer simulations, which is quite exciting.'

Researchers from Nazarbayev University in Kazakhstan and Hong Kong Polytechnic University have demonstrated a new 4-step process including (i) spin-coating of the precursors; (ii) cryogenic treatment; (iii) blow-dry process for the removal of the solvent; and (iv) thermal annealing. This process is a straightforward and effective technique which can yield homogenous perovskite films without the use of anti-solvents and regardless of the complexity of the precursor compositions.

When mixed perovskite precursor solutions are evaporated, usually non-uniform films with poor morphology are obtained due to coalescence of perovskite crystallites during rapid solvent removal. Therefore, anti-solvents are usually used to preapare mixed perovskite thin films. However, this technique is not convenient for large-scale manufacturing in industry since the final perovskite film quality critically depends on multiple parameters while adding the anti-solvent. Inaccurate control of the mixing process will cause gradients in over-saturation of the precursor solution, leading to spatially inhomogeneous nucleation of the perovskite and deterioration of the resultant film quality. Furthermore, commonly used anti-solvents such as chlorobenzene or toluene are environmentally harmful and highly toxic. The team's new method circumvents these issues and offers an improved alternative that enhances the control over the perovskite growth process, decoupling the nucleation and crystallization phases.

Swansea University researchers have declared a perovskite solar module the size of an A4 sheet of paper, (nearly six times bigger than 10x10 cm² modules of that type reported before), developed by using simple and low-cost printing techniques. The accomplishment shows that the technology works at a larger scale, not just in the lab, which is crucial for commercial use.

The team works for the SPECIFIC Innovation and Knowledge Center led by Swansea University. The researchers used an existing type of cell, a Carbon Perovskite Solar Cell (C-PSC), made of different layers - titania, zirconia and carbon on top - which are all printable. Though their efficiency is lower than other perovskite cell types, C-PSCs do not degrade as quickly, which has been established through 1 year of stable operation under illumination.

Researchers at Penn State have gained new insight into how halide perovskite materials enable the efficient conversion of sunlight into electricity.

Scientists state that halide perovskites tend to have a unique tolerance for imperfections in their structures, which allows them to efficiently convert sunlight into electricity when other materials with similar imperfections do not. What makes these materials so tolerant of imperfections, however, was unknown prior to this study. The researchers used ultrafast infrared imaging technology to investigate how the structure and composition of these materials influence their ability to convert sunlight into electricity.

Researchers at the Energy Materials and Surface Sciences Unit at the Okinawa Institute of Science and Technology Graduate University (OIST) have designed a new method to fabricate low-cost high-efficiency solar cells. Prof. Yabing Qi and his team from OIST, in collaboration with Prof. Shengzhong Liu from Shaanxi Normal University, China, developed the cells using perovskite materials.

In what Prof. Qi defines as "the golden triangle," solar cell technologies need to fulfill three conditions to be worth commercializing: their conversion rate of sunlight into electricity must be high, they must be inexpensive to produce, and they must have a long lifespan. Today, most commercial solar cells are made from crystalline silicon, which has a relatively high efficiency of around 22%. Though silicon, the raw material for these solar cells, is abundant, processing it tends to be complex and shoots up the manufacturing costs, making the finished product expensive.

Researchers from the Chinese Academy of Sciences have designed perovskite solar cells with power conversion efficiency of 18.1% by adding Titanium (Ti) cathode layer.

Two different device configurations including n-i-p and p-i-n have been adopted for fabricating the PSCs. As organic electron transport layers (ETLs), fullerene and its derivatives (C60 and PCBM) play an important role in efficient PSCs with p-i-n structure (ITO/Hole transport layers/perovskite/ETLs/Cathode). However, the cathode metal atoms diffuse through the organic ETLs to the perovskite layer, causing degradation of PSCs. Also, the instability and high-cost of organic ETLs were limiting factors for the commercialization of PSCs. Considering these problems, the research team led by Dr. LI Xinhua, developed the ultra-thin Ti cathode interlayer to replace organic ETLs for fabricating efficient and low-cost PSCs.