Wideband photovoltaic energy conversion using group III-nitrides

An intersubband transition based quantum cascade structure has been presented for wideband photovoltaic energy conversion. The structure is designed on group III-nitride material system so that the large conduction band offset of the material system can be utilized to absorb light over a broad energy range, and the ultra-fast electron scattering rates can be utilized to collect the photo-excited carriers at the terminals at a faster rate. The designed structure that we present here has an absorption linewidth of ~200 meV with center at ~700 meV. The carrier transport time is less than 1.5 ps in a single stage, where several such stages can be cascaded to increase the absorption. Therefore, we find that short-circuit current, open-circuit voltage, and power density at the operating point of the designed structure are significantly large.