Abstract This review highlights the development of energy saving transparent heat regulating (THR) materials and coating for energy saving window applications. Current state-of-the-art technologies including transparent heat reflecting mirror (THM), thermo-chromic (TC), transparent solar cells (TSC), and luminescent based materials have been discussed. The coating performance primarily depends on the selection of materials, surface and structural morphology, dielectric passivation growth process and architecture of the multi-layered structure. The micro-structural properties of thin metal/metal oxide layer, and its impact on the heat reflecting coating have been studied extensively. Growth of high quality continuous thin film with fewer defects is an essential part of the infrared reflecting and/or heat regulating coatings. Henceforth, in this review, detailed analysis of growth of continuous and thin metal layer influence of the seed layer (germanium and nickel) and doping on the growth mechanism of thin metal have been discussed. Surface morphology and electronic properties of metal layer/multi-layered coatings have been studied in detail for THR applications. A wide range of metal oxides and their physical properties have been considered for use as passivation layer in the THR coating structure. Among several THR structures, the architecture comprising of dielectric-metal-dielectric (DMD) stack is known to exhibit the best heat reflecting performances. While the metal component typically comprises of silver (Ag), copper (Cu), and nitride based materials, dielectrics are made from metal oxides such as BaSnO3, TiO2, SnO2, ZnO, HfO2, Cu2O, and ZrO2. Selection of passivation layer and tuning of micro-structural properties are very crucial to enhance the visible transmittance without sacrificing infrared reflectance. Optical properties of the dielectric layer can be controlled with growth mechanism and varying content of impurity dopant. Metal doped dielectrics play a key role to enhance the visible light transmission while maintaining infra-red reflection. Through in-situ materials engineering, crystal quality of the dielectric improves which has significant role on the THR performance. Furthermore, impact of rapid thermal annealing (RTA) technique to improve crystal quality of metal oxides without oxidizing the thin metal layer is also emphasized. In the subsequent sections, synthesis of thin films by using sputtering methods, thermal evaporation and e-beam evaporation methods using inexpensive materials for large scale deployment of coating have been discussed. Neutral colored Cu-based THR smart windows is developed through tuning the structural property of TiO2. The simulated Cu-based THR window shows ≥10 °C temperature reduction when compared to conventional glass based windows. Thermal stability of copper and silver based multilayer enhanced through ultra-thin metal and dielectric interface engineering. Transparent conducting oxides (TCOs) are also an essential candidate for the wide band gap semiconductor based THR application. Recent progress in TCOs material has been briefly discussed in one of the section of the review. Hetero-epitaxy of metal oxides (ITO/ZnO) shows promising characteristics as heat insulating materials. Impact of growth process and surface morphology of the TCO have been studied to evaluate the performance of the TCO as heat insulating materials. In addition, advanced hybrid composite based heat reflector coatings for energy efficient building applications is also highlighted in the later section of the review. The industrial utilization and efficacy of heat reflector metal oxides, when incorporated into polymeric/pigments/fibers and heat reflecting durable paints as advanced hybrid composites coatings has been discussed. The progression of solution based metal nanowire (MNW) and optical properties for the heat regulating applications have been included. Dielectric/metal-NW/dielectric multilayer can be a potential candidate for the development of low cost THR film. The solution based THR methods has potential to be mass customized in economic ways and can be viable at industrial scale. Thermo-chromic materials are also considered as prospective candidate for the transparent coating applications. Recent development of VO2 bilayer, trilayer, micro-pattern and nano-plate films have been discusses to enhance the luminous transmittance and solar modulation ability. Transparent solar cells, based on the infra-red absorption through up-conversion nanoparticles are viable candidates for the development of environmental friendly heat regulating systems. Recent advancement of inorganic, polymer, perovskite, and luminescent based transparent solar cell (TSCs) with heat reflecting mirror have been evaluated for smart windows applications. For the deployment of large scale THR film, low cost materials, roll-to-roll (R2R) sputter and atmospheric pressure chemical vapour deposition (APCVD) have been assessed for the industrial applicability. The progression of THR materials with thermo-chromics, self-cleaning and TSCs materials can enhance the overall performance of the smart/transparent coatings for thermal management and heat regulating functionalities.

中文翻译：

---

用于节能窗应用的透明热调节 (THR) 材料和涂层：材料设计、微结构和界面质量对 THR 性能的影响

摘要 本综述重点介绍了用于节能窗应用的节能透明热调节（THR）材料和涂层的发展。已经讨论了当前最先进的技术，包括透明热反射镜 (THM)、热致变色 (TC)、透明太阳能电池 (TSC) 和基于发光的材料。涂层性能主要取决于材料的选择、表面和结构形态、介电钝化生长过程和多层结构的结构。金属/金属氧化物薄层的微观结构特性及其对热反射涂层的影响已得到广泛研究。具有较少缺陷的高质量连续薄膜的生长是红外反射和/或热调节涂层的重要组成部分。今后，在这篇综述中，详细分析了连续薄金属层生长对种子层（锗和镍）的影响以及掺杂对薄金属生长机制的影响。已经详细研究了用于 THR 应用的金属层/多层涂层的表面形态和电子特性。已经考虑将多种金属氧化物及其物理特性用作 THR 涂层结构中的钝化层。在几种 THR 结构中，已知由电介质-金属-电介质 (DMD) 堆叠组成的架构具有最佳的热反射性能。虽然金属成分通常包括银 (Ag)、铜 (Cu) 和氮化物基材料，但电介质由金属氧化物制成，例如 BaSnO3、TiO2、SnO2、ZnO、HfO2、Cu2O 和 ZrO2。钝化层的选择和微结构特性的调整对于在不牺牲红外反射率的情况下提高可见光透射率至关重要。介电层的光学特性可以通过生长机制和不同的杂质掺杂物含量来控制。金属掺杂的电介质在增强可见光透射率同时保持红外反射方面起着关键作用。通过原位材料工程，电介质的晶体质量得到改善，这对 THR 性能具有重要作用。此外，还强调了快速热退火 (RTA) 技术在不氧化薄金属层的情况下提高金属氧化物晶体质量的影响。在随后的部分中，使用溅射方法合成薄膜，已经讨论了使用廉价材料大规模部署涂层的热蒸发和电子束蒸发方法。中性色铜基 THR 智能窗是通过调整 TiO2 的结构特性开发的。与传统的玻璃基窗相比，模拟的铜基 THR 窗显示出≥10°C 的温度降低。通过超薄金属和介电界面工程增强铜和银基多层膜的热稳定性。透明导电氧化物 (TCO) 也是基于宽带隙半导体的 THR 应用的重要候选材料。TCO 材料的最新进展已在审查的其中一节中进行了简要讨论。金属氧化物的异质外延 (ITO/ZnO) 显示出作为绝热材料的良好特性。已经研究了 TCO 的生长过程和表面形态的影响，以评估 TCO 作为隔热材料的性能。此外，本综述的后面部分还重点介绍了用于节能建筑应用的先进混合复合材料热反射涂层。已经讨论了热反射金属氧化物在作为高级混合复合材料涂层并入聚合物/颜料/纤维和热反射耐用涂料中时的工业用途和功效。包括基于溶液的金属纳米线 (MNW) 和用于热调节应用的光学特性的进展。电介质/金属纳米线/电介质多层膜可以成为开发低成本 THR 薄膜的潜在候选者。基于解决方案的 THR 方法具有以经济方式大规模定制的潜力，并且可以在工业规模上可行。热致变色材料也被认为是透明涂层应用的潜在候选者。已经讨论了 VO2 双层、三层、微图案和纳米板薄膜的最新发展，以提高透光率和太阳能调制能力。基于通过上转换纳米粒子吸收红外线的透明太阳能电池是开发环境友好型热调节系统的可行候选者。具有热反射镜的无机、聚合物、钙钛矿和基于发光的透明太阳能电池 (TSC) 的最新进展已被评估用于智能窗户应用。用于大规模 THR 薄膜、低成本材料的部署，卷对卷 (R2R) 溅射和大气压化学气相沉积 (APCVD) 已被评估为工业适用性。THR 材料与热致变色、自清洁和 TSCs 材料的发展可以提高智能/透明涂层的整体性能，用于热管理和热调节功能。