SCIENCE CHINA Materials•2026•DOI: 10.1007/s40843-026-4381-5
Bismuth telluride (Bi2Te3)-based alloys remain the benchmark for low-temperature thermoelectric applications, yet their conversion efficiency is limited by the trade-off between electrical and thermal transport. This study introduces a pseudo grain boundary engineering strategy to simultaneously enhance the average figure of merit (ZT) in p-type (Bi,Sb)2Te3 (BST) materials. By incorporating Ag-based compounds, the carrier concentration is optimized via substitution of Ag+ ions, while the introduction of secondary phases at grain boundaries effectively suppresses lattice thermal conductivity. The approach yields a peak ZT of 1.35 at 393 K and an average ZT of 1.25 across 303–483 K, representing a significant improvement over pristine BST. Compared to prior reports, this work achieves superior average ZT while maintaining high electrical conductivity, addressing the longstanding bottleneck of thermal conductivity reduction without compromising carrier mobility. The findings underscore the efficacy of pseudo grain boundary engineering in advancing Bi2Te3-based thermoelectrics for solid-state cooling and power generation.
SCIENCE CHINA Materials•2025•DOI: 10.1007/s40843-025-3423-6
Copper sulfide (Cu2−xS) is a low-cost, eco-friendly thermoelectric material, but its performance is limited by the trade-off between electrical conductivity and thermal conductivity. This study introduces an intermediate doping strategy using copper alloys (bronze, cupronickel, brass) to partially replace the copper source in Cu1.8S, addressing excessive Cu vacancies. The approach enhances the solubility limits of Zn, Sn, Pb, and Ni, optimizing carrier concentration, and generates in situ nanoscale second phases that scatter phonons. The optimal composition, Cu1.8S + 5 wt.% bronze + 3 wt.% cupronickel + 2 wt.% brass, achieves a ZT of 1.7 at 673 K, a 247% improvement over pristine Cu1.8S and the highest reported for this system. This work establishes intermediate doping as a viable paradigm for optimizing thermoelectric properties in alloy-based systems.
SCIENCE CHINA Materials•2025•DOI: 10.1007/s40843-025-3410-9
Dion-Jacobson (DJ) phase two-dimensional (2D) perovskites offer superior stability and structural diversity but suffer from limited charge transport, impeding device performance. This study rationally designed and synthesized six diammonium spacer cations and their corresponding DJ-phase 2D perovskite single crystals to elucidate how spacer characteristics—heterocyclic type and amino substitution position—govern structure-property-stability relationships. Meta-substituted amino groups induce a tilted cation configuration that reduces interlayer spacing, weakens hydrogen bonding, and lowers lattice distortion, thereby enhancing carrier generation and transport. Thermal stability is dictated by both steric hindrance from branched side chains and the heterocycle nature: flexible aliphatic rings buffer thermal deformation, dissipate internal stress, and improve overall stability. Humidity stability tests (15–40% RH, 60 days) showed negligible degradation, with no PbI2 diffraction peaks. Photostability under 1 sun LED (50 h, 25–35% RH) revealed unchanged XRD patterns except for slight weakening in (4AMP)PbI4. Thermal stability under nitrogen (180°C, 30 min) confirmed that alicyclic cations, specifically (3AMP)PbI4 and (4AMP)PbI4, exhibited no detectable PbI2 peaks, whereas other films degraded. Damp heat testing (85°C, 85% RH, 40 h) further validated the superior stability of aliphatic diammonium-based perovskites. These findings establish clear design rules for spacer cations to overcome charge transport limitations while maintaining robust stability.