Raman-based strategies for improved solar cell optics

Strongly Raman shifting silicon and diamond particles were investigated. Diffuse reflecting films were prepared with each particle system. The diffuse reflecting films provided the necessary long light path lengths for the observation of Raman scattering by photovoltaic cell. Germanium photovoltaic cells were used with silicon particles and diamond particles were used silicon solar cells to better observe Raman scattering in spectral regions where the particle systems do not absorb light. Particle systems provide greater anti-Stokes to Stokes ratio as compared to bulk crystal. The anti-Stokes to Stokes ratio increases with decreasing particles size and/or with increasing probe beam intensity. This result is not due to particle heating since it can be observed in spectral regions where the Raman probe beam is not absorbed. Diamond particles produce the most pronounced spectral shift perhaps due its larger Raman shift relative to silicon.