Lead-free

Over the past five years, six Fraunhofer Institutes combined their expertise in the Fraunhofer lighthouse project "MaNiTU" to identify the most sustainable paths to market of perovskite-silicon tandem solar cells made of stable materials and manufactured using scalable production processes. They were able to show that high cell efficiencies can be achieved using industry-oriented processes, however, they found that such high efficiencies were only currently achievable with lead perovskite materials. Based on these findings, the researchers developed suitable recycling concepts to ensure sustainability.

In the "MaNiTU" project, the Fraunhofer researchers produced new materials with perovskite crystal structures and compared them with existing materials at the cell level. The comparisons showed that high efficiencies can only be achieved with lead perovskites. They then successfully fabricated highly efficient demonstrators, for example, a perovskite silicon tandem solar cell of more than 100 square centimeters with screen-printed metallization and produced mini modules for single and interconnected tandem solar cells. Subsequent life cycle analyses showed that by using suitable production and recycling processes and degradation rates comparable to today's silicon technology, it is feasible to make a sustainable product.

Researchers from India's Madan Mohan Malaviya University of Technology, University of Delhi, Manipal University and Sweden's IAAM have combined 2D and 3D perovskites to strengthen both reliability and efficiency of 3D perovskite solar cells (PSCs). 

The team explored the combined effect of Dion-Jacobson (DJ) 2D-3D halide-based perovskites layers on device performance. The DJ 2D material used was PeDAMA₄Pb₅I₁₆, while the 3D material is the lead-free, stable CsGeI_3-xBr_x (with x=1). The optimized solar cell structure developed in this work consisted of (Au/Cu₂O/PeDAMA₄Pb₅I₁₆/CsGeI_3-xBr_x/PCBM/FTO). 

Researchers from China's Jiangxi Normal University, Chinese Academy of Sciences (CAS) and City University of Hong Kong have developed a self-driven X-ray detection device using high resistivity zero-dimensional lead-free perovskite ferroelectric single-crystal (NMP)₃Sb₂Br₉. The device exhibits an excellent self-driven X-ray detection performance, with an ultra-low detection limit of 84.1 nGyair/s, approximately 60 times lower than that of commercial α-Se (5500 nGyair/s).

The self-driven detection mode without external bias has been proven to be an effective means of reducing the limit of detection (LoD) due to its low current noise characteristics. Additionally, the zero-dimensional distinctive isolated framework results in a high resistivity of 1.39 × 1011 W cm, which effectively reduces the current noise and suppresses ion migration. 

A Research Group led by Prof. Eva Unger at Helmholtz Zentrum Berlin (HZB), in collaboration with the Indian Institute of Technology Bombay and University of Jammu, has reported the use of inkjet printing to fabricate thin films of combinatorial mixed formamidinium tin-lead perovskites and evaluated their layer quality and device performance. The team focused on optimizing the inkjet-printing process to ensure precise film deposition and enhance device performance.

Image credit: ACS Applied Materials and Interfaces

The scientists deposited Sn/Pb intermixed FASn_1–xPb_xI₃ (x = 0.25, 0.5, and 0.75)-based perovskite thin films through inkjet printing. The study focused on finding the ideal composition ratio for a favorable photovoltaic performance. The deposited FASn_1–xPb_xI₃ thin films were subjected to various characterizations followed by their implementation in solar cells. 

Zinc-ion batteries (ZIBs) are emerging as a candidate for use as an efficient and sustainable energy storage solution, offering advantages in terms of cost-effectiveness, safety, and performance. The key to commercializing ZIBs lies in developing cathode materials that offer high specific capacity and prolonged cycle performance. 

In a recent study, researchers from the Indian Institute of Science and University of Melbourne have demonstrated the capability of environmentally friendly, lead-free inorganic perovskites for high-rate rechargeable aqueous zinc-ion batteries with enhanced stability and excellent rate performance.

Researchers from China's Shaanxi Normal University, Zhejiang Normal University, China Institute of Radiation Protection and Chinese Academy of Sciences have developed lead-free photoferroelectric hybrid metal halide perovskite flexible membranes for wearable detectors, that offer excellent X-ray response with high sensitivities, low detection limit and impressive imaging capabilities. 

Demonstration and application potential for lead-free photoferroelectric perovskite membrane (LFPPM). a) Optical images of the LFPPM. b) Schematic diagram of LFPPM wearable X-ray dosimeter. c) Schematic diagram of the working principle of wearable X-ray dosimeter. (Image credit: Nanowerk)

High-sensitivity wearable radiation detectors are important for personnel protection in radiation environments such as defense, nuclear facilities, and medical fields. Traditional detectors using bulk crystals tend to lack flexibility. Hybrid metal halide perovskites have shown promise for next-generation radiation detection as they can efficiently absorb high-energy radiation and convert it into electrical signals. However, there are concerns of lead toxicity. More recent efforts have explored lead-free alternatives, but these have generally suffered from poor charge transport properties, reducing their effectiveness as radiation detectors.

Researchers from India's Chiktara University have reported improved stability and performance of organic-inorganic perovskite solar cells by applying a strategy called bandgap grading.

The method is based on enabling the cell perovskite absorber to collect a wider range of light photons by modifying its thickness and characteristics. The team explains that its recent study demonstrates the effectiveness of both linear and parabolic bandgap grading strategies in optimizing light absorption and boosting performance, showing its potential. 

Lead-halide perovskites hold great promise as the next generation of PVs, but unstable lead exposure through gas, water, and soil accumulation could have detrimental consequences if not properly controlled and recycled as perovskite use expands globally. There are also stability issues limiting operational lifetime for lead-perovskite devices themselves. Researchers have attempted to replace lead with slightly less toxic tin, but thus far tin-based perovskites still suffer from air instability. Without breakthroughs in stability and environmental safety, scaling perovskite solar technology could flood our waste stream with hazardous materials. Now, researchers from CHOSE (Centre for Hybrid and Organic Solar Energy) at the University of Rome Tor Vergata have addressed the concerns regarding toxicity and recyclability associated with the lead contained in perovskite solar cells. 

Image credit: ACS Energy Letters 

The scientists may have found a solution in a new lead-free antimony-based perovskite solar cell design. Their recent research demonstrates a mixed-cation perovskite-inspired material (PIM) that boosted efficiency by 81% compared to conventional cesium-only antimony solar cells, while also exhibiting unmatched stability.

Researchers from Japan's University of Electro-Communication and CAR MATE MFG. CO. have developed a lead-free tin sulfide solar cell that is intended for applications in tandem perovskite-silicon PV devices. 

Using a new passivation technique based on the use of phenylsilane (PhSiH₃) as a reducing agent, the scientists were able to considerably increase the cell's efficiency compared to a reference device with no PhSiH₃ treatment.

Researchers from Southeast University and the University of Liberal Arts Bangladesh have designed and simulated an all-inorganic lead-free tandem photovoltaic cell based on copper, indium, gallium and selenium (CIGS) thin-film technology and perovskite.

The proposed top cell (a) and bottom cell (b), image from Heliyon

The novel device architecture is said to have the potential to reach a power conversion efficiency of 38.39%. “The main objective of this work is to find an efficient combination of non-toxic solar cells with high efficiency so that it saves time and effort before going for fabrication,” the scientists said in their work, noting that the perovskite and materials used for the cell are lead-free.