The large spectral tuning range and strong oscillator strength of the coherent electron oscillations in localized surface plasmon resonance (LSPR) make it highly attractive for the enhancement of solar energy conversion efficiency. While the large scattering cross section of LSPR has been used successfully to increase light trapping at energies above the band edge, large enhancements in spectral conversion below the band edge have proven more difficult. If the plasmon does not scatter incident radiation, the absorbed energy can be transferred to the semiconductor by direct transfer of hot plasmonic electrons, or, as shown recently by our group, through the nonradiative plasmon induced resonant energy transfer (PIRET). Whereas hot electron transfer can occur after the plasmon has decayed, PIRET is mediated by the strong local electromagnetic field during the coherent oscillations of the plasmon. Both mechanisms allow an enhancement in photoconversion at energies below the band edge of the semiconductor.
In this presentation we systematically investigate the PIRET mechanism by combining transient absorption spectroscopy and action spectrum photocatalysis/IPCE measurements. A varying SiO barrier in Au@SiO@CuO core shell nanoparticles is used to determine the distance dependence of the plasmon-semiconductor coupling. Next the effect of spectral overlap in the semiconductor-LSPR coupling is investigated in a FeO/Au hole array composite. Additionally, the effect of the interface on the PIRET excited carriers is investigated in Au@CuO and Ag@CuO nanoparticles. The results are compared to theory in order to guide optimal design for enhancing below band edge solar energy conversion through LSPR and PIRET.