Dependence of plasmonic enhance- ment of photocurrent in a-Si:H on the position and thickness of SiNx spacer layers

Plasmonic interfaces integrated to the front, back and both surfaces of photovoltaic thin films show different degrees of enhancement of light trapping. Enhancements in the spectral dependence of photocurrent normalized to the power of excitation light are used as an indicator of enhanced light trapping. In a previous study, we obtained enhancement in the spectral range of 600-700 nm by integrating 100-nm Ag nanoparticles to the back surface of a-Si:H with a critical dependence on the SiNx spacer layer thickness. In this study, we compare the enhancement in photocurrent due to plasmonic interfaces integrated to the front, back and both front and back surfaces of the a-Si:H absorber. Interfaces integrated to the back result in the largest enhancement in photocurrent while those integrated to the front give the lowest. The marginal enhancements due to two interfaces appear to be mainly due to the back interface. While plasmonics effects may not account for the total enhancement in photocurrent, it explains the relative enhancement in the spectral range of 550-700 rather well. For all configurations, the enhancement in the spectral dependence of photocurrent is accompanied by broadening into the red of the localized surface plasmon resonance (LSPR). (© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)