Ion Enrichment-Mediated Charge Transfer in CNTs-Based Films for Infrared Electrochromism

In response to a rapidly changing background environment, carbon nanotubes (CNTs)-based infrared electrochromic materials have emerged as a research focus due to their fast response kinetics and high flexibility. Nevertheless, the microscopic mechanism governing the relationship between infrared emissivity and applied bias voltage remains vague. In this work, a defect-engineering strategy is employed to fabricate sulfur/nitrogen co-doped CNTs (SNCNT) films as a model system for mechanism investigation. It is revealed that the core process lies in ion enrichment-mediated charge transfer, regulating macroscopic conductivity. Specifically, accumulated ions can dynamically reconstruct the film architecture, facilitating ion-electron interactions within an electrical double-layer capacitive framework. This process presents an asymmetric operation mechanism that anions induce hole doping, while cations promote electron doping. First-principles calculations further correlate ion-specific modulation with orbital energy depth and π-conjugation degree. By integrating these insights, a multi-dimension qualitative model is proposed to correlate infrared emissivity with interfacial contact resistance, charge-transfer dynamics, and atomic-scale structure. The optimized SNCNT film system demonstrates an infrared modulation width of Δε = 0.601, accompanied by notable bia-removal memory behavior (Δε/Δt = -0.0018 s^-1), underscoring its potential in infrared camouflage, information encryption, and electromagnetic shielding.