Design on a Novel Titanium Dioxide Irregularly Distributed Bragg Reflector for Thin Film Silicon Solar Cells.

Titanium dioxide, which leads an excellent optical performance, is proposed to design irregularly distributed Bragg reflector (IDBR) through theoretical simulation as well as experimental verification. Firstly, a primary distributed Bragg reflector (DBR) model with the titanium dioxide serving as low reflection layer in, and amorphous silicon as high reflection layer is analyzed. The titanium dioxide DBR shows much enhanced reflection bandwidth relative to the DBR with silicon dioxide. A further study suggests that a traditional titanium dioxide IDBR demonstrate much enhanced performance versus the silicon dioxide IDBR with similar structure. Besides, the reflection bandwidth of the IDBR, especially in the high wavelength range, is dramatically promoted with respect to the DBR. Finally, a novel gradient IDBR model is developed. The simulation results reveal a higher reflection bandwidth of the titanium dioxide gradient IDBR than the silicon dioxide one. The reflectance of the titanium dioxide gradient IDBR is up to 90% in a range by 300 to 1450 nm. And, the reflection bandwidth of the gradient IDBR is much improved respect to the traditional IDBR. It seems that the titanium dioxide gradient IDBR could be an efficient selection for the thin film silicon solar cells. Finally, the gradient IDBR were fabricated via plasma enhanced chemical vapor deposition (PECVD) on a silicon wafer. A further test demonstrates a reflectance over 95% in the range from 400 to 1400 nm, and verifies the simulation results.