Purcell effect and luminescent downshifting in silicon nanocrystals coated back-contact solar cells

Abstract

Silicon nanocrystals show a significant shift between the strong absorption in the blue–ultraviolet region and their characteristic red–near-infrared emission as well as space separated-quantum cutting when short wavelength photons are absorbed. These two effects can be used to increase the efficiency of crystalline silicon solar cells. We fabricated high quality interdigitated back-contact crystalline silicon solar cells in an industrial pilot line and coated them with optimized silicon nanocrystals layers in a cost effective way. Here we demonstrate an increase of 0.8% of the power conversion efficiency of the interdigitated back-contact cell by the silicon nanocrystals layer. In addition, we prove that this increase is due to a combination of a better surface passivation, a better optical coating, and of the luminescent downshifting effect. Moreover we demonstrated that the engineering of the local density of photon states, thanks to the Purcell effect, is instrumental in order to exploit this effect.