A Multilevel Intermediate-Band Solar Cell by InGaN/GaN Quantum Dots with a Strain-Modulated Structure

摘要

The Ⅲ-Nitride semiconductor In_xGa_(1-x)N has the unique advantage of the widest adjustment of direct bandgaps from the infrared (InN at 0.65 eV) to the ultraviolet (UV) (GaN at 3.42 eV) region. Compared with Si, GaAs, CuInGaSe, or Ge systems, it is the only semiconductor system that provides the perfect match to the solar spectrum, which opens up an interesting opportunity for high-efficiency photovoltaic applications. InGaN-based alloys also have the favorable physical properties of high absorption coefficient (～10~5 cm~(-1)), high radiation resistance, high drift velocity, and high carrier mobility. The theoretical power conversion efficiency of a four-junction solar cell based on InGaN is expected to be more than 50% according to the balance modeling estimation. However, the current high value for solar conversion efficiency devices is achieved by using a multi-junction tandem approach in Ⅲ-Ⅴ semiconductors.