Interface Modification in Type-II ZnCdSe/(Zn)CdTe QDs for High Efficiency Intermediate Band Solar Cells*

Intermediate band solar cells have been proposed as being able to overcome the Shockley-Queisser limit for single junction solar cells.¹ Our group has been devolving a II-VI based material system using type-II submonlayer quantum dots (QDs) composed of (Zn)CdTe embedded in a ZnCdSe host. These materials, when lattice matched to InP closely match the theoretically predicted requirements. However, do to the dissimilar group VI elements and Cd desorption that occurs during the formation of the quantum dots a highly strained interfacial layer is formed.² A new growth process is proposed to avoid formation of a strain-inducing ZnSe interfacial layer. We show that the new growth sequence allows for improved control of the interfacial composition and simplifies the fabrication of the intermediate band solar cell device structure based on these QDs, since additional strain balancing schemes are no longer required to grow stress-free structures.
[1] A. Luque, and A. Marti, Phys. Rev. Lett., 78, 5014 – 5017 (1997).
[2] S. Dhomkar, et al., Journal of Vacuum Science & Technology B, Nano. and Micro.: Mat., Process., Meas., and Phen., 31(3), 03C119 (2013).