Application of thin epitaxial hydrogenated si layers to high efficiency heterojunction solar cells on N-type si substrates

We show that a thin (<;20nm) stack comprised of n⁺ doped hydrogenated crystalline silicon (c-Si:H) and n⁺ doped hydrogenated amorphous silicon (a-Si:H) can provide an effective back-surface-field for heterojunction solar cells on n-type crystalline silicon (c-Si) substrates. The c-Si:H and a-Si:H layers were grown in the same plasma-enhanced chemical vapor deposition (PECVD) reactor at deposition temperatures close to 200°C. This technique was used to fabricate heterojunction solar cells with open-circuit voltages over 700mV and active-area conversion efficiencies of 21.4% on n-type c-Si substrates.