Lead-free

Researchers from Southeast University in Bangaladesh and U.S-based Rochester Institute of Technology have examined the performance of a lead-free Cs₂TiX₆-based n–i–p type heterostructure perovskite solar cell design, performed using a one-dimensional device simulator, also known as the SCAPS-1D. 

The design makes use of Cs₂TiCl₆ as an n-type front absorber, Cs₂TiI₆ as an I (intrinsic)-layer absorber and Cs₂TiBr₆ as a p-type absorber. NiO (p) and ZnO (n) are utilized as the hole transport material and electron transport material. The fluorine-doped tin oxide (FTO) acts as a front contact, conductive oxide, while Pt (platinum) is used as the back contact. 

Researchers from Zhengzhou University and the Chinese Academy of Sciences (CAS) have devised a novel lead capturing technique for perovskite solar cells: they implanted a multifunctional mesoporous amino-grafted-carbon net into the perovskite solar cells, creating biomimetic cage traps that could effectively mitigate Pb leakage and shield from external invasion under extreme weather conditions. 

The team then explored the synergistic Pb capturing mechanism in terms of chemical chelation and physical adsorption. Additionally, the Pb contamination assessment of end-of-life perovskite solar cells in the real-world ecosystem, including Yellow River water and soil, was proposed by the scientists. 

Researchers from China's Zhejiang University and South China University of Technology have developed transparent glassy composites based on lead-free anti-perovskites in a novel approach that could revolutionize X-ray imaging.

There is a high demand for high-resolution and ultrastable X-ray imaging methods in various fields, like material inspection, medical diagnostics, astronomical discovery, and scientific research. This demand has ignited a vigorous pursuit of innovative X-ray-responsive materials that must possess exceptional qualities such as high X-ray attenuation, efficient scintillation, rapid light decay, and robust durability. Among them, lead-halide-based perovskites have emerged as a compelling contender due to their remarkable luminescence efficiency, superior X-ray attenuation capabilities, and short fluorescence lifetimes. However, their application in the scintillation field is hindered by the toxicity of heavy metal lead (Pb), low photon yield caused by self-absorption effects, and poor X-ray irradiation stability.

Project SUNREY (”Boosting SUstaiNability, Reliability and EfficiencY of perovskite PV through novel materials and process engineering”) is a three-year project which started on November 1, 2022. It is coordinated by the Fraunhofer Institute for Applied Polymer Research IAP in Potsdam, Germany. The project aims to further the development of highly-efficient solar cells based on non-critical raw materials (with a focus on making perovskite solar cells more sustainable, efficient and durable) and to strengthen the innovation potential of the European industry. 

SUNREY is funded by the European Union’s research and innovation program Horizon Europe within the framework of the Green Deal Initiative with 4.25 Million Euro. 

Researchers from Nanyang Technological University, Singapore (NTU Singapore) and the Institute of Materials Research and Engineering (IMRE) at the Agency for Science, Technology and Research (A*STAR) in Singapore have developed a method for capping materials based on non-toxic metals being used in the manufacture of perovskite solar cells.

(Left) A diagram showing the different layers of the perovskite solar cell capped with the zinc-based capping material fabricated by the researchers. (Right) The dotted green rectangle indicates the active region of the perovskite solar cell that captures sunlight and converts it to electricity. Image: NTU Singapore / Nature Energy

Perovskite solar cells are made of several layers of materials, including a perovskite layer that harvests light and a capping layer. The capping layer is coated onto the perovskite layer to protect the solar cell from environmental stresses such as heat and moisture and to boost the performance of the cell. To ensure that the capping layer is compatible with the underlying perovskite layer, researchers typically use an approach called the half precursor (HP) method to fabricate the capping layer. One of the precursor chemicals is first deposited on top of the perovskite layer which provides the other precursor. Through a process known as cation exchange reaction, the deposited precursor then reacts with lead ions present in the perovskite layer beneath to form a lead-based chemical compound that makes up the capping layer. As a result of the HP method, lead is also present in the protective capping layer. A method that enables non-toxic metals to be used in the capping layer could be a game-changer for perovskite solar cells.

A research team from City University of Hong Kong (CityU), Curtin University, National Taiwan University, Huazhong University of Science and Technology, Nankai University and Polish Academy of Sciences recently developed a lead-free perovskite photocatalyst that delivers highly efficient solar energy-to-hydrogen conversion.

The team unveiled the interfacial dynamics of solid-solid (between halide perovskite molecules) and solid-liquid (between a halide perovskite and an electrolyte) interfaces during photoelectrochemical hydrogen production. The latest findings open up an avenue to develop a more efficient solar-driven method for producing hydrogen fuel in the future.

Researchers at the Research Institute of Sweden (RISE) and KTH Royal Institute of Technology have presented the ionic liquid (IL) synthesis of two novel pseudo-2D perovskite-type gold(III)polyiodide compounds and their use as active layers in monolithic solar cells.

The team stated that its recent work represents the first demonstration of film deposition of gold iodide/polyiodide compounds onto porous monolithic substrates with subsequent solar cell characterization. The devices reportedly showed promising photovoltaic performance and could unlock new materials design possibilities, ultimately moving away from lead-based photovoltaic materials. These findings further highlight the use of simple polyiodide entities to increase the structural and electronic dimensionality of gold perovskite-type anions.

Scientists at the University of California at Berkeley and the US Department of Energy's Lawrence Berkeley National Laboratory have developed a perovskite-structured ferroelectric compound that might be suitable for the production of lead-free perovskite solar cells.

“The new ferroelectric material – which is grown in the lab from cesium germanium tribromide (CsGeBr₃ or CGB) – opens the door to an easier approach to making solar cell devices,” the team said. “Unlike conventional solar materials, CGB crystals are inherently polarized, where one side of the crystal builds up positive charges and the other side builds up negative charges, no doping required.”

Scientists at the University of California San Diego, Lawrence Berkeley National Laboratory, Stanford University, Los Alamos National Laboratory, Korea's Yonsei University and Daegu Gyeongbuk Institute of Science and Technology have developed a novel perovskite solar cell, made of a lead-free low-dimensional perovskite material with a superlattice crystal structure. The material exhibits efficient carrier dynamics in three dimensions, and its device orientation can be perpendicular to the electrodes. Materials in this particular class of perovskites have so far only exhibited such dynamics in two dimensions—a perpendicularly orientated solar cell has never been reported.

The team reported that thanks to its specific structure, this new type of superlattice solar cell reaches an efficiency of 12.36%, which is the highest reported for lead-free low-dimensional perovskite solar cells (the previous record holder’s efficiency is 8.82%). The new solar cell also has an unusual open-circuit voltage of 0.967 V, which is higher than the theoretical limit of 0.802 V. Both results have been independently certified.

Scientists at Nanyang Technological University in Singapore (NTU) and Tsinghua University have developed a stretchable and waterproof ‘fabric’ that turns energy generated from body movements into electrical energy. The fabric contains a polymer that, when pressed or squeezed, converts mechanical stress into electrical energy. It is also made with stretchable spandex as a base layer and integrated with a rubber-like material to keep it strong, flexible, and waterproof.

The team showed that tapping on a 3cm by 4cm piece of the new fabric generated enough electrical energy to light up 100 LEDs. The fabric can withstand washing, folding and crumpling without performance degradation, and it could maintain stable electrical output for up to five months, demonstrating its potential for use as a smart textile and wearable power source.