Optimized design of silicon thin film solar cells with silicon nanogratings

To increase the performances of thin film solar cells, we show how nanophotonics concepts can be used to silicon nanogratings into effective photon management layers for solar cells. This is accomplished by patterning the silicon nanogratings present on thin film solar cell that support optical resonances. These resonances can be exploited to concentrate randomly polarized sunlight or to effectively couple it to guided and diffracted modes. Our optimization reveals that light absorption of thin film solar cell with silicon nanogratings is enhanced in randomly polarized sunlight. The simulated short-circuit current density (Jsc) over the solar spectrum shows an up to 127% enhancement when comparing with bare thin film cell. The average Jsc enhancement under an unpolarized illumination is almost immune to the incident angle ranging from −40° to 40°. It is interesting that Jsc enhancement of normal incident is not the maximum. The advantages of film solar cell with silicon nanogratings over plasmonic solar cell will be discussed.