Lead-free

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.

A research team, led by Professor Iván Mora Seró from the Institute of Advanced Materials (INAM) of the Universitat Jaume I of Castelló, has improved the efficiency and durability of tin perovskite solar cells. The cells presented in the recent study exceeded 1,300 hours of operational stability, thanks to the incorporation of additives in the preparation of the devices.

Tin-based halide perovskites are being studied as potential candidates for lead-free perovskite solar cells. In the case of tin, an efficiency of more than 14% has been achieved so far, but it has major stability problems. This new work has introduced a combination of dipropylammonium iodide and sodium borohydride, two additives that have made it possible to prepare devices with PCEs of more than 10%, which boast greater stability and have maintained 96% of the initial PCE after 1,300 hours under solar illumination in a nitrogen atmosphere.

A team from Israel's Technion Institute of Technology has announced the development of self-healing perovskite nanocrystals.

Having to frequently replace electronics due to malfunctioning of materials is unavoidable today, since every device suffers from degradation as a result of defects that accumulate during use over time. This generates, in addition to customer frustration and costs, a heavy environmental footprint.

An international research team from TU Dortmund University, the Russian Academy of Sciences and ETH Zurich has discovered that the electron dynamics in perovskite crystals are largely determined by lead. This discovery suggests that replacing this element could enable better control of the crystals' material properties.

TU Dortmund University Professor Dmitri Yakovlev's group investigated ultrafast interaction processes between optically excited charge carriers and their surroundings in perovskite crystals. The team was able to show that the magnetic properties can be regulated on an ultrafast time scale through the use of optical pulses with a duration of trillionths of a second. This proof that they can be controlled is of particular interest for possible new applications.