590
22 Light-to-Electricity Conversion
Fig. 22.1 Principle of photocatalytic activity. Light absorption creates an electron-hole pair. The electron and hole
diffuse and can recombine in the bulk or at the surface. Free carriers can react at the surface with species from the
surrounding solution, reducing an electron acceptor or oxidizing a donor species. Adapted from [1816]
Fig. 22.2 SEM images of MOCVD-grown a ZnO thin film and b ZnO nanoneedle layer. c Comparison of the photocatalytic activity (decoloration of the dye Orange II in aqueous solution) of the ZnO thin film (irradiation with a Hg
lamp for 5 h and 15 h) and the ZnO nanoneedles (irradiation 5 h). The sample labeled ‘control’ (scaled to 100%) is the
start situation (absorption of the dye Orange II) without photocatalytic process. Adapted from [1819], reprinted with
permission
In sun-protection cream only the UV absorption is wanted in UVA (330–420 nm) and UVB (260–
330 nm) ranges. Subsequent photocatalysis on the skin and the presence of radicals are unwanted.
Thus the semiconductor particles (∼10–200 nm diameter) are encapsulated in microbeads (∼1–10 µm
diameter) of silica, PMMA or urethane, also improving ease of dispersion, aggregation, stability and
skin feel.
22 Light-to-Electricity Conversion
Fig. 22.1 Principle of photocatalytic activity. Light absorption creates an electron-hole pair. The electron and hole
diffuse and can recombine in the bulk or at the surface. Free carriers can react at the surface with species from the
surrounding solution, reducing an electron acceptor or oxidizing a donor species. Adapted from [1816]
Fig. 22.2 SEM images of MOCVD-grown a ZnO thin film and b ZnO nanoneedle layer. c Comparison of the photocatalytic activity (decoloration of the dye Orange II in aqueous solution) of the ZnO thin film (irradiation with a Hg
lamp for 5 h and 15 h) and the ZnO nanoneedles (irradiation 5 h). The sample labeled ‘control’ (scaled to 100%) is the
start situation (absorption of the dye Orange II) without photocatalytic process. Adapted from [1819], reprinted with
permission
In sun-protection cream only the UV absorption is wanted in UVA (330–420 nm) and UVB (260–
330 nm) ranges. Subsequent photocatalysis on the skin and the presence of radicals are unwanted.
Thus the semiconductor particles (∼10–200 nm diameter) are encapsulated in microbeads (∼1–10 µm
diameter) of silica, PMMA or urethane, also improving ease of dispersion, aggregation, stability and
skin feel.