Singh Dipti Umed, Narayanan Remya
Deprtment of Physics and Centre for Energy Science, Indian Institute of Science Education and Research, Pune Maharashtra 411008, India.
Department of Environmental Science, Savitribai Phule Pune University, Pune 411007, Maharashtra, India.
Nanotechnology. 2021 Nov 18;33(6). doi: 10.1088/1361-6528/ac33d4.
Vanadium dioxide is a potential candidate for energy efficient smart windows and have crystalline phase transition temperature () at 68 °C. So far, literatures mainly emphasis on different synthetic strategies of tungsten doped VOwhich is a most effective dopant to reduceof VOto near room temperatures. Until now, there is no report shows the incorporation of flexible 1D photonic crystals as spectrally selective, temperature tunable device to control the changes in optical transmission modulations of W-VOnanostrtcures, especially in the near IR region for smart window application. W-doped VOwith various tungsten contents were synthesized with a facile hydrothermal route. We found that, with 1.1 at% of tungsten doping in intrinsic VO, the metal to insulator transition temperature is brought down to 37 °C from 68 °C. IR transmission of VOthin film can be reduced from 70% to 40% around room temperature, after doping. Significant absorption enhancement has been observed for both VOand W-doped VOfilms, deposited over tunable SiO/TaObased distributed Bragg reflector (DBR) fabricated over flexible PET (poly-ethylene terephthalate) substrates. On depositing VOover ∼70% reflecting DBR, optical transmission is reduced to ∼15% from 35% while the temperature varies to 380 K from 300 K in IR regime. Number of stacks plays a crucial role for effective IR extinctions. A high quality DBR is fabricated by increasing no. of stacks from 4 to 7, with optical transmission of DBR reduced to nearly 5% in stop band. However, with 1.1 at% of W-VOover such 95% reflecting flexible DBR, optical transmission vanishes nearly, around room temperature itself in the stop bands of that DBR, which clearly indicates the significant absorption enhancement. W-VO/DBR hybrid can substantially modulate the solar heat flux and also imbuing DBR over flexible PET substrates offers retrofitting of the existing windows for energy economy. Thus these structures have promising potential applications for optical devices and practical design for smart windows.
二氧化钒是节能智能窗的潜在候选材料，其晶相转变温度为68°C。到目前为止，文献主要关注钨掺杂VO₂的不同合成策略，钨是将VO₂的转变温度降低到接近室温的最有效掺杂剂。到目前为止，尚无报道表明将柔性一维光子晶体作为光谱选择性、温度可调器件用于控制W-VO₂纳米结构的光传输调制变化，特别是在用于智能窗应用的近红外区域。采用简便的水热法合成了具有不同钨含量的W掺杂VO₂。我们发现，在本征VO₂中掺杂1.1 at%的钨后，金属-绝缘体转变温度从68°C降至37°C。掺杂后，VO₂薄膜在室温附近的红外透过率可从70%降低到40%。在柔性聚对苯二甲酸乙二酯（PET）衬底上制备的可调谐SiO₂/Ta₂O₅基分布式布拉格反射器（DBR）上沉积的VO₂和W掺杂VO₂薄膜，均观察到显著的吸收增强。在约70%反射率的DBR上沉积VO₂时，在红外波段，当温度从300 K变化到380 K时，光传输从35%降低到约15%。堆叠层数对有效的红外消光起着关键作用。通过将堆叠层数从4增加到7，制备了高质量的DBR，其在阻带中的光传输降低到近5%。然而，在这种95%反射率的柔性DBR上沉积1.1 at%的W-VO₂时，在该DBR的阻带中，室温附近光传输几乎消失，这清楚地表明吸收显著增强。W-VO₂/DBR混合结构可以大幅调制太阳热通量，并且在柔性PET衬底上赋予DBR可对现有窗户进行节能改造。因此，这些结构在光学器件方面具有广阔的潜在应用前景，并且是智能窗实际设计的理想选择。
