Theoretical enhancement of solar cell efficiency by the application of an organic 'down shifting' thin film

Abstract

Poor ultraviolet (UV) quantum conversion efficiency contributes to a reduction in the efficiency of silicon based photovolatic cells. In the UV, the main loss mechanism is through surface recombination of photo-generated carriers due to the shallow absorption depth of high energy photons. One method of utilising the UV region is by downshifting UV photons to lower energies where the quantum efficiency for silicon is higher. It is proposed that the organic pigment lumogen yellow S0790 (lumogen) can be used as a suitable down shifting optical thin film in conjunction with silicon based photovoltaic cells. A theoretical determination of the upper limiting efficiency enhancement which lumogen can provide single junction silicon based cells as been determined. The results show an absolute increase in efficiency of 4% over an adapted form of the Shockley Queisser detailed balance limit.