Absorption and scattering effects by silver nanoparticles near the interface of organic/inorganic semiconductor tandem films
- 773 Downloads
We experimentally and theoretically characterize back-scattering and extinction of Ag nanoparticle (AgNP) arrays on both Si wafer substrates and optically-thick Ag substrates with and without organic poly(3-hexylthiophene):[6,6]-phenyl C61-butyric acid methyl ester (P3HT:PCBM) bulk-heterojunction thin film coatings. A strong red-shift in back-scattered light wavelength occurs from AgNP arrays on Si as a function of increasing mean nanoparticle diameter (ranging from 30 to 90 nm). Back-scattering from the AgNP array is notably quenched in the wavelength range of strong P3HT absorption when the organic layer is applied. However, back-scattering is enhanced to a degree relative to the uncoated AgNP array on Si at wavelengths greater than the absorption band edge of P3HT. For comparison, the optical properties of AgNPs on an optically-thick Ag substrate are reported with and without P3HT:PCBM thin film coatings. On the reflective Ag substrates, a significant enhancement (by a factor of 7.5) and red-shift of back-scattered light occurred upon coating of the AgNPs with the P3HT:PCBM layer. Additionally, red-edge extinction was enhanced in the P3HT:PCBM layer with the presence of the AgNPs compared to the planar case. Theoretical electromagnetic simulations were carried out to help validate and explain the scattering and extinction changes observed in experiment. Both increasing nanoparticle size and an increasing degree of contact with the Si substrate (i.e., effective index of the nanoparticle environment) are shown to play a role in increasing back- and forward-scattering intensity and wavelength, and in increasing absorption enhancements in both the organic and Si layers. AgNPs placed at the P3HT:PCBM/Si interface give rise to absorption increases in P3HT of up to 18 %, and only enhance Si absorption at wavelengths longer than the absorption band edge of P3HT (by almost 90 % in the 660–1,200 nm wavelength range). These results provide insight into how metal nanoparticles placed near an organic/inorganic interface can be employed for light management in tandem or hybrid organic/inorganic thin-film semiconductor configurations for solar energy harvesting applications or light detection applications.
KeywordsSilver nanoparticles Conjugated polymer Silicon Light scattering Absorption Surface plasmons Organic
The authors gratefully acknowledge support from National Science Foundation Grant No. 0903661 “Nanotechnology for Clean Energy IGERT,” a Corning Inc. graduate fellowship, Rutgers’ Institute for Advanced Materials Devices and Nanotechnology, Rutgers’ Aresty Undergraduate Research Fellowship Program, Rutgers’ Research in Science and Engineering (RiSE) Scholarship Program and a Rutgers' Research Council Grant. The authors thank Binxing Yu, Jesse Kohl, Sarah Goodman, and Manika Jain for useful discussions.
- Bohren CF, Huffman DR (2004) Absorption and scattering of light by small particles. Wiley, WeinheimGoogle Scholar
- Gan G, Bartoli FJ, Kafafi ZH (2013) Plasmonic-enhanced organic photovoltaics: breaking the 10% efficiency barrier. Adv Mater. doi: 10.1002/adma.201203323
- O’Carroll DM, Collopy AX, Ferry VE, Atwater HA (2010) Surface plasmon assisted absorption in conjugated polymer thin films and devices. In: 25th European Photovoltaic Solar Energy Conference and Exhibition, Valencia, pp 834–837Google Scholar
- Palik ED (1985) Handbook of optical constants of solids. Academic Press, BostonGoogle Scholar