Fayad Remi, Halaoui Lara
Department of Chemistry, American University of Beirut, Beirut, 110236, Lebanon.
Chemphyschem. 2016 Jan 18;17(2):260-9. doi: 10.1002/cphc.201500942. Epub 2015 Dec 8.
We investigate the cause of amplification of light-energy conversion when coupling a nc-TiO2 film to a TiO2 inverse opal by comparing it to an inverse TiO2 glass (i-TiO2 -g) fabricated with the exact monodisperse air-hole size as an inverse opal with a stop band at 600 nm (600-i-TiO2 -o). A significant twofold average gain in the photon-to-current conversion efficiency is measured to the red of the stop band at the 600-i-TiO2 -o/nc-TiO2 bilayer under front-wall and back-wall illumination, greater than the gain within the stop band. A smaller amplification is measured under front-wall illumination-and no gain is measured under back-wall illumination-for i-TiO2 -g/nc-TiO2 at these energies. The photonic crystal therefore causes trapping of light through the bilayer, not only within the gap but also to the red, at frequencies within its dielectric band. This light-trapping effect is found to be dependent on structural order, as a highly disordered inverse glass film with the same air-hole size and thickness does not yield the same gain. A drop in the transmission of light is measured within the same frequencies to the red of the stop band upon adding nc-TiO2 to 600-i-TiO2 -o, consistent with light trapping in the bilayer.
通过将纳米晶二氧化钛（nc-TiO2）薄膜与二氧化钛反蛋白石耦合，与具有精确单分散气孔尺寸的反蛋白石结构的二氧化钛玻璃（i-TiO2 -g）进行比较，我们研究了光能转换放大的原因，该反蛋白石结构的二氧化钛玻璃在600 nm处有一个禁带（600-i-TiO2 -o）。在600-i-TiO2 -o/nc-TiO2双层结构的前壁和后壁照明下，在禁带红色区域测得光子到电流转换效率有显著的两倍平均增益，大于禁带内的增益。在这些能量下，对于i-TiO2 -g/nc-TiO2，在前壁照明下测得的放大倍数较小，而在后壁照明下未测得增益。因此，光子晶体不仅在禁带内，而且在其介电带内的频率下，通过双层结构导致光的捕获，不仅在禁带内，而且在红色区域。发现这种光捕获效应取决于结构有序性，因为具有相同气孔尺寸和厚度的高度无序的反玻璃薄膜不会产生相同的增益。在将nc-TiO2添加到600-i-TiO2 -o中后，在禁带红色区域的相同频率内测得光传输下降，这与双层结构中的光捕获一致。
