Absorption and transport via tunneling in quantum-well solar cells

Absorption and tunneling are two major physical processes contributing to photocurrent generation in solar cells. Many new “ultra-high efficiency” PV devices utilize quantum effects to enhance their efficiency. This paper calculates the impact of quantum effects on the absorption and tunneling current as a function of electric fields and light trapping ratios. Results show that increasing electric fields enhance tunneling of photogenerated carriers, which dominates over the opposing effect of reduced absorption. Also, the significant advantage of light enhancement over increasing the number of quantum wells (QWs) has been demonstrated. These calculations allow optimizing the tunneling photocurrents in design of QW solar cells.