Lead-free

Researchers from Tokyo's Institute of Science and Idemitsu Kosan recently reported a single‑particle photophysics study of colloidal BaZrS₃ chalcogenide perovskite quantum dots (QDs), targeting them as a lead‑free, stable alternative to halide perovskites for light‑emitting applications. BaZrS₃ offers a direct, visible‑range bandgap and robust chemical stability, and the key question here was how quantum confinement and surface defects govern its emission at the single‑QD level.

Structural and optical characterization. (a) Photo of BaZrS₃ QD toluene suspension; (b) powder XRD data of BaZrS₃ QDs (red) and BaZrS₃ reference (blue); (c) TEM image of the synthesized BaZrS₃ QDs; (d) size dispersion analyzed from the TEM images for 109 QDs; (e) high-resolution TEM image of a single QD showing the lattice fringes and d -spacing; (f ) absorption (blue) and PL (orange) spectra (normalized) of the BaZrS₃ QD toluene suspension; (g – i) high-resolution XPS spectra for the Ba 3d (g), Zr 3d (h), and S 2p (i) core levels, fitted as described in the text. Image from: Nanoscale

The team synthesized colloidal BaZrS₃ QDs by a hot‑injection method and obtained particles in the BaZrS₃ crystal phase with a broad size distribution from 2 nm to 18 nm (average 7.6 nm). This broad size range spans strong to weak quantum‑confinement regimes and is reflected in ensemble optics: weak PL (solution PLQY ≈ 5%) with peaks at 491 nm and 504 nm plus a red shoulder, consistent with a mixture of sizes and local environments. Composition analysis showed nearly ideal Ba:Zr ≈ 1:1 but significant sulfur deficiency, pointing to abundant surface traps that can quench emission and currently limit device‑ready performance.

Henan University researchers have developed lanthanide-based, lead-free double perovskite nanocrystals that combine ultra‑narrow green emission with record‑high efficiency and excellent stability, targeting next‑generation high‑definition displays and scintillators. 

The key challenge they address is that while lead halide perovskite nanocrystals offer excellent PLQY and narrow emission, their toxicity and poor environmental stability are serious drawbacks, and most lead‑free double perovskites either have broad self‑trapped‑exciton emission with low PLQY or, in the lanthanide‑based case, very weak absorption which limits practical brightness.

Researchers from Fudan University, Donghua University, Tongji University, City University of Hong Kong, Suzhou Laboratory and Australia's Himalaya Energy have developed a new class of non-fullerene electron transport layers (ETLs) designed to boost the performance and stability of tin-based perovskite solar cells.

Fullerene-based ETLs are widely used in tin-based perovskite solar cells for their strong electron extraction capabilities, but they often face hurdles such as high cost, complex synthesis, low electron mobilities and limited interfacial compatibility. To overcome these challenges, the team introduced fluorinated triple-acceptor polymers (P1, P2, and P3) as a low-cost, high-mobility alternative. These polymers form continuous, conformal interfaces with tin perovskites, enabling stronger and more uniform interactions across large areas.

Researchers from the University of Potsdam, HZB, Humboldt University of Berlin and The Chinese University of Hong Kong recently took a step toward understanding and improving the stability of perovskite solar cells. Despite their impressive efficiencies, lead-based perovskite solar cells still struggle with long-term instability and the inherent toxicity of lead. These issues stem largely from mobile halide ions within the perovskite structure, which migrate under operational conditions, leading to device degradation.

To tackle this challenge, the team investigated ion migration in four representative perovskite compositions: pure lead-based, mixed lead–tin, and two tin-based perovskites synthesized using different solvents (DMSO and DMF–DMI). Their detailed quantitative measurements revealed striking differences in ion density and mobility across these materials. The lead-based perovskites exhibited the highest ion densities, while incorporation of tin reduced these values slightly. Tin-based perovskites processed with DMSO showed further improvement, but the real breakthrough came from those prepared using the DMF–DMI solvent, which displayed an ion density almost ten times lower than in the lead-based counterparts.

Researchers from Fudan University, Nanjing University of Science and Technology, Tongji University, Taiyuan University of Technology, Shanghai Nanoshine Technology, Donghua University and Shanghai University of Engineering Science have reported a milestone in the development of lead-free perovskite photovoltaics through the design of high-performance tin-based perovskite solar cells (TPSCs). Their work demonstrates a record certified power conversion efficiency (PCE) of 17.71% for inverted TPSCs.

Tin-based perovskite absorbers are widely recognized as promising alternatives to their lead-based counterparts due to their lower toxicity, environmental friendliness, and high theoretical efficiency. However, progress in this domain has been hindered by poor interfacial contact, suboptimal hole extraction, and instability caused by facile oxidation of Sn²⁺. To address these challenges, the research team engineered a molecular interfacial modifier, (E)-(2-(4',5'-bis(4-(bis(4-methoxyphenyl)amino)phenyl)-[2,2'-bithiophen]-5-yl)-1-cyanovinyl)phosphonic acid, to improve both interfacial and film quality within inverted-architecture TPSCs.

Developing efficient and stable lead-free perovskite solar cells (PSCs) has become a research goal as environmental concerns arising from the toxicity of lead-based perovskite solar cells persist. However, lead-free alternatives tend to lag behind their lead-based counterparts in terms of performance. In addition, despite the perovskite grain shape and structure plays a significant role in photon absorption, little to no significant dedicated research has been conducted to explore shape-driven photovoltaic properties of PSCs. 

To address these issues, researchers from China's Wenzhou University have utilized COMSOL Multiphysics software to investigate the perovskite grain shape-modulated photovoltaic optimization aiming to systematically enhance the overall performance of lead-free all-perovskite tandem solar cells (APTSCs). 

Metal halide perovskites' narrow emission spectrum, strong light absorption, brightness, and facile tunability make them ideal candidates for color-conversion layers in displays. Unlike conventional quantum dots, perovskites can achieve high-purity color emission with significantly thinner layers, enabling efficient conversion of blue light into red and green without the need for external color filters. This reduces system complexity while increasing brightness and color accuracy.

Researchers from Sungkyunkwan University, Pohang University of Science and Technology (POSTECH), University of Cambridge and University of Oxford have shown that perovskite films can absorb over 99.9% of incident blue light while generating vivid, stable emission, all with lead content kept below the Restriction of Hazardous Substances (RoHS) threshold. The research demonstrates that a perovskite layer only one-fifth the thickness of conventional quantum-dot films provides effective color conversion, paving the way toward more compact and efficient devices. Moreover, the integration of optical strategies such as light scattering structures, photonic crystals, dimensional control, and photon recycling further enhances performance.

The development of luminescent solar concentrators (LSCs) has been hindered by the drawbacks of conventional fluorescent glasses that rely on embedded nanocrystals, including high production costs, solvent-intensive fabrication, and poor recyclability.  Researchers at Nankai University, Tianjin University and Shanghai Re-poly Environmental Protection Technology have now introduced a lead-free perovskite derivative, ETP₂SbCl₅, that addresses these challenges by combining efficiency, recyclability, and low-cost preparation.

ETP₂SbCl₅, a yellow-emissive perovskite derivative synthesized via a simple room-temperature solution process, can undergo thermal treatment to form fluorescent glasses. Ab initio molecular dynamics revealed structural distortions in the [SbCl₅] pyramids during phase transitions (α → β → glass), which directly influence luminescence by broadening and red-shifting the emission. This mechanism allows efficient absorption of ultraviolet light (<420 nm) and enables photoluminescence with a quantum yield of ~52.6%.

Researchers at Tampere University in Finland have launched a new project, NEBULAE, funded through the Horizon Europe Marie Skłodowska-Curie Actions Postdoctoral Fellowships programme. Led by Dr. Khaldoon Nasser, the project seeks to develop next-generation, eco-friendly materials that can boost the performance of solar cells while also opening opportunities in photonics.

At the heart of NEBULAE is an innovative use of lead-free perovskite nanocrystals. Traditional perovskite solar cells absorb mainly visible light, leaving the near-infrared portion of the solar spectrum largely untapped. NEBULAE aims to change this by embedding ytterbium-doped perovskite nanocrystals into glass materials.

Researchers from National Taiwan University, National Synchrotron Radiation Research Center and Academia Sinica have developed a strategy for enhancing the performance and stability of tin-based perovskite transistors by incorporating porphyrin-like additives. 

The research team focused on two additives: H₂Pc and SnPc, both of the phthalocyanine family and known for their strong chemical stability and ability to interact with metal ions. When added to perovskite precursor solution, they help suppress the oxidation of tin ions and improve overall film quality. As a result, the transistors exhibited significantly higher charge mobility (up to 4.40 cm² V⁻¹ s⁻¹) and improved resistance to environmental degradation. The additives also increased grain sizes and reduced defects, which are critical for efficient charge transport.