Influence of barrier layer’s height on the performance of Si quantum dot solar cells

Abstract

We investigated the influence of the barrier layer height in silicon quantum dot superlattice (Si-QDSL) solar cells on the cell performance by two-dimensional device simulation taking into account the quantum size effect. Although at Si-QD diameters (d) of 5 and 10 nm better cell performance was obtained as the barrier height increased, in the case of d = 3 nm, the efficiency decreased as the barrier height increased. Further investigation showed that the band mismatch at the interface between Si-QDSL and the n-type layer degraded open-circuit voltage (Voc) at d = 3 nm. After the optimization of the physical properties of the n-type layer, Voc was improved to 1.43 V and the bandgap-Voc (Woc) offset became about 0.4 V, suggesting that the band mismatch is the significant factor for the Voc loss. From these results, it was found that careful selection of n- or p-type materials is necessary when the strong quantum confinement effect occurs in Si-QDSL.