High-efficiency InAs/GaAs quantum dot solar cells by MOCVD

Quantum dot solar cells can potentially realize ultrahigh efficiencies in single p-n junction structures utilizing intermediate-level energy bands. However, so far most fabricated quantum dot solar cells have suffered from severe reduction of open-circuit voltage by incorporation of quantum dots resulting in significantly lower efficiencies than those without quantum dot. Here we fabricate a high-efficiency InAs/GaAs quantum dot solar cell. Our cell contains five layers of high-density (4 × 10¹⁰ cm^-2 per layer) self-assembled InAs quantum dots grown by metalorganic chemical vapor deposition suppressing open-circuit-voltage degradation. We develop a dual-layer anti-reflection coating of optimum thicknesses. The resulting cell exhibits efficiencies of 18.7% under AM1.5G, 1 sun and 19.4% for 2 suns, the highest reported thus far, for any kind of quantum dot cell. Our high-efficiency demonstration in a cell grown by MOCVD is a strong encouragement towards the commercialization of quantum dot solar cells.