[7p-S21-1~22] 13.10 Compound solar cells

▼ [7p-S21-10] Extended Carrier Lifetime in InGaAs/GaNAs Multiple Quantum Well Solar Cells with Free-barrier Conduction Band Structure

〇(DC)WARAKORN YANWACHIRAKUL¹, NAOYA MIYASHITA², HASSANET SODABANLU², KENTAROH WATANABE², YOSHITAKA OKADA^1,2, MASAKAZU SUGIYAMA², YOSHIAKI NAKANO¹ (1.Grad. School of Eng., The Univ. of Tokyo, 2.RCAST, The Univ. of Tokyo)

Keywords:Free-barrier Conduction Band, Diluted-Nitride Solar Cells, Carrier Lifetime

A 1.2-eV strain-balanced free-barrier conduction band (FB-CB) InGaAs/GaAsN multiple quantum well (MQW) improved the carrier transport in the diluted-N active layer in term of the increase of carrier lifetime and the absence of electron confinement. Because a degradation of carrier transport caused by a short carrier lifetime becomes a trade-off to apply the diluted-N materials for solar cells, the InGaAs/GaNAs MQW, where thin layers with and without diluted-N were stacked alternatively, was introduced to mitigate the drawback of short carrier lifetime. In addition, by adjusting an In and N composition, the FB-CB structure without electron confinement was targeted to keep carrier collection preferable. The results showed a longer non-radiative recombination electron lifetime and a slightly larger open-circuit voltage of the FB-CB MQW compared to that of the thin-film InGaNAs cell. These results suggested that this novel structure is potentially applicable to the active layer of three-junction solar cells based on the Ge bottom cell.