硅酸盐学报2026，Vol.54Issue(2)：457-467,11.DOI:10.14062/j.issn.0454-5648.20250253
无机非金属类红外透明导电薄膜的研究进展
Development on Inorganic Non-Metallic Infrared Transparent Conductive Films
摘要
Abstract
Transparent conducting films(TCFs)as materials that uniquely combine high optical transmittance and high electrical conductivity within a target electromagnetic spectrum become indispensable components in a myriad of modern optoelectronic devices.The development of TCFs operating in the visible light spectrum is a mature field,both in fundamental understanding and in widespread commercial application.These materials being ubiquitous in flat-panel displays,touch screens,and photovoltaics are predominantly based on wide-bandgap oxide semiconductors.A degenerate semiconductor state is achieved via introducing a high concentration of dopants(heavy doping)into a host matrix such as tin-doped indium oxide(i.e.,ITO,In2O3:Sn),aluminum-doped zinc oxide(i.e.,AZO,ZnO:Al),or fluorine-doped tin oxide(i.e.,FTO,SnO2:F),providing a substantial free-carrier conductivity,while maintaining the wide bandgap transparency to visible photons.Despite this success,the frontier of TCFs for the infrared(IR)spectrum remains in a nascent,exploratory stage.This stands in a stark contrast to the significant and urgent demand for such materials in critical military and civilian sectors.In military applications,the strategic advantage is twofold,i.e.,the forward-looking radomes of airborne IR search-and-track(IRST)systems and the windows of missile-borne IR precision guidance systems require a coating that is simultaneously transparent to incident IR radiation(for target acquisition)and electrically conductive.This conductivity provides an effective mechanism for radar cross-section reduction,conferring radar stealth capabilities.In the civilian domain,IR TCFs characterized by a challenging combination of low carrier concentrations and exceptionally high carrier mobility are a key enabling material for the next generation of high-efficiency optical modulators.Such components are essential for expanding the operational bandwidth of optical communications further into the mid-and far-infrared wavelengths.The primary obstacle hindering progress is the perceived incompatibility of infrared transparency and high electrical conductivity.These two properties are governed due to the free-carrier behavior,often leading to a detrimental trade-off:the very carriers required for conductivity tend to reflect IR photons via the free-carrier.Consequently,a comprehensive synergistic mechanism to co-optimize these properties is still unclear,and the fabrication of an IR TCF with ideal,well-rounded performance remains an elusive goal.In the aforementioned application demands,it is imperative to develop a deeper theoretical framework for the synergistic mechanisms governing IR transparency and conductivity,which can,in turn,guide the design and fabrication of superior IR TCFs. This review firstly elucidates the fundamental solid-state physics governing infrared transparency and electrical conductivity in semiconductor materials.A detailed analysis of the Drude model reveals that the key material parameters affecting the performance are the plasma frequency(ωp).A high conductivity(σ=ne2τ/m∗)demands a high carrier concentration(n)and a low effective mass(m*).Conversely,IR transparency requires the plasma frequency(ωp2=ne2/ε0m∗)to be lower than the frequency of the incident IR light,which necessitates a low n and a high m*.This review concludes that resolving this trade-off hinges on the effective modulation of three key variables,i.e.,carrier concentration(n),carrier m∗,and carrier scattering frequency(γ).Subsequently,the review systematically introduces the established and emerging methods for manipulating these physical parameters. To address the inherent conflict between IR transparency and conductivity,this review analyzes two prevailing design strategies currently being pursued in the field.The first strategy retains the use of oxide semiconductors as a host material platform but introduces sophisticated modification methods designed to achieve exceptionally high carrier mobility,while maintaining a carefully optimized,moderate carrier concentration.This approach seeks to maximize conductivity via the mobility term rather than the concentration term,thereby mitigating free-carrier reflection.For N-type semiconductors,a research focus has pivoted from conventional p-block dopants(like Al,Sn,F)to d-block transition metal elements(i.e.,Mo,W)and interstitial hydrogen(H).These dopants show a promising potential in minimizing ionized impurity scattering and other defects,thus significantly enhancing carrier mobility.For P-type semiconductors that are notoriously difficult to realize as TCFs due to localized states and large hole effective masses,researchers leverage a valence band modification theory.The hybridization of orbitals at the valence band maximum(VBM)is altered via doping with elements in the same group as the material's anion.This modification aims to increase the VBM's dispersion(i.e.,reduce its curvature),which directly translates to a smaller hole effective mass(mh∗)and a substantial increase in hole mobility. The second strategy represents a paradigm shift away from conventional oxides.It employs a design principle centered on achieving synergy between far-infrared(FIR)transparency and conductivity via increasing the material's high-frequency(optical)dielectric constant(ε∞).A high ε∞ effectively screens the free carriers,suppressing the plasma frequency and shifting the plasma edge to longer wavelengths,even at high carrier concentrations.This approach has identified a class of materials with an outstanding potential for IR TCF applications(i.e.,heavy metal chalcogenides and their solid solutions,particularly those exhibiting octahedral coordination(i.e.,Bi2Se3,Bi2Te3)via establishing a clear relationship between chemical bonding,crystal structure,and ε∞.These materials possess highly polarizable bonds that yield the requisite high ε∞,opening a promising avenue for circumventing the limitations of conventional oxides. Summary and Prospects While visible-spectrum TCFs are mature,IR TCFs still face some challenges in reconciling transparency and conductivity.This review outlines two primary synergistic mechanisms that provide foundational design principles for a family of IR TCFs.However,this field remains nascent.Future development will likely be driven by two key thrusts,i.e.,1)The acceleration of material discovery via high-throughput computational screening,which demands the identification of accurate descriptors,and 2)The development of novel low-loss IR TCFs,characterized by low carrier concentrations and high mobility,which requires a deeper mastery of carrier transport mechanisms.These advancements are critical for enabling next-generation IR modulators,optical communications,and sensing technologies.关键词
红外/透明导电/电磁屏蔽Key words
infrared/transparent and conducting/electromagnetic shielding分类
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吴彬,段超,黄易,高岗,朱嘉琦..无机非金属类红外透明导电薄膜的研究进展[J].硅酸盐学报,2026,54(2):457-467,11.基金项目
国家自然科学基金项目(5203000545). （5203000545）
