Effect of Dot Height Truncation on the Device Performance of Multilayer InAs/GaAs Quantum Dot Solar Cells
The effect of dot height truncation on the device performance of multilayer InAs/GaAs quantum dot solar cells is investigated. The different structures were grown by chemical beam epitaxy, and an indium flush process is used to control the dot height. A series of ten layer samples with dots truncated at a height of 5 and 2.5 nm, respectively, are studied. Luminescence, atomic force microscopy, and high resolution scanning transmission electron microscopy results indicate that the quantum dot properties are preserved up to the tenth layer for both structures. Under 1 sun illumination, the truncation of the dot height to 2.5 nm increased the short circuit current density by 0.7 mA/cm2 and the open circuit voltage by 31 mV. From the external quantum efficiency curves, limited to wavelengths> 500 nm, a 1.46 mA/cm2 current density enhancement is found over a GaAs reference cell. At least 45% of this enhancement has been attributed uniquely to the presence of quantum dots in the structure.
IEEE Journal of Photovoltaics