In the light absorption spectra (shown in Figure 4a), it could be found that it is these nanoparticles that resulted in the enhancement of the light absorption of the devices. Figure 3 Surface SEM image, EDS spectrum, and XRD pattern of a CIGS layer. The CIGS layer was deposited at a substrate temperature Vorinostat chemical structure of 400°C for 3 min. (a) The surface SEM images of the CIGS layer, (b) the analysis results of the EDS spectrum of the

CIGS nanoparticle at the position marked by a white cross in (a), and (c) the XRD pattern of the CIGS layer shown in (a). Figure 4 Schematic of LSPR light trapping, UV-vis absorption spectra, and PL spectra. (a) Schematic of LSPR light trapping for a hybrid system of ITO/CIGS/P3HT:PCBM in which the CIGS nanoparticles are embedded between the ITO substrate and P3HT:PCBM photoactive layer. (b) The UV-vis absorption spectra of ITO/CIGS, ITO/P3HT:PCBM, and ITO/CIGS/P3HT:PCBM. (c) The PL spectra of ITO/P3HT:PCBM and ITO/CIGS/P3HT:PCBM. To investigate the effects

of the CIGS nanoparticles on the light absorption and charge separation efficiency of the conjugated polymer active layers, we measured the UV-visible-infrared absorption and PL spectra of the P3HT:PCBM layers with and without the CIGS interlayers (prepared on ITO-glass substrates). Figure 4b AP26113 purchase displays the absorption spectra of CIGS/ITO, P3HT:PCBM/ITO, sum of CIGS and P3HT:PCBM, and P3HT:PCBM/CIGS/ITO. Obviously, the CIGS interlayer enhances the light absorption of the P3HT:PCBM active layer in the spectral range of 300 to 650 nm.

More importantly, the absorption intensity of P3HT:PCBM/CIGS/ITO is much larger than that of the sum of CIGS/ITO and P3HT:PCBM/ITO. It should be noted that the thickness of the P3HT:PCBM monolayer is approximately equal to that of the CIGS/P3HT:PCBM bilayer (about 100 nm) according to the cross-sectional SEM image (see Figure 2c), i.e., the enhancement of light absorption is not due to the thickness change of the P3HT:PCBM layer. Moreover, the CIGS interlayer absorbs only very little incident light. Therefore, most of the increased Gefitinib supplier absorption should come from the P3HT:PCBM close to the interfaces between the P3HT:PCBM and CIGS nanoparticles. The mechanism may be C646 in vitro similar to the localized surface plasmon resonant (LSPR) effect [16–20]. It has been known that the excitation of the LSPR through the resonant interaction between the electromagnetic field of incident light and the surface charge of metallic nanostructures causes an electric field enhancement (that can be coupled to the photoactive absorption region) and increases the absorption of photoactive conjugate polymer or organic semiconductor [21–23]. The above results demonstrate that the semiconductor CIGS nanoparticles may also exhibit LSPR effect just as metallic nanostructures do.