Thursday, November 5, 2009: 11:20 AM
Brahma (Camino Real Hotel)
InGaN alloys have been well established as active materials for light-emitting diodes (LEDs) and laser diodes with emission wavelengths covering from near UV to green spectral regions. InGaN alloys recently emerged as a new solar cell materials system due to their tunable energy band gaps (varying from 0.7 eV for InN to 3.4 eV for GaN, covering almost the whole solar spectrum) and superior photovoltaic characteristics (direct energy band gap in the entire alloy range and high carrier mobility, drift velocity, radiation resistance, and optical absorption of ~105 cm−1 near the band edge). We will discuss here the growth, fabrication and photovoltaic characteristics of InGaN solar cells by exploiting InGaN/GaN multiple quantum wells (MQWs) with In contents exceeding 0.3, attempting to alleviate to a certain degree the phase separation issue and demonstrate solar cell operation at wavelengths longer than previous attainments (>420 nm). The fabricated solar cells based on In0.3Ga0.7N/GaN MQWs exhibited an open circuit voltage of about 2 V, fill factor of about 60%, and an external efficiency of 40% (10%) at 420 nm (450 nm). Further effects of nanostructures in the light absorbing layer which enhance efficiency will be discussed.