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Power conversion efficiency of thin-film microcrystalline silicon solar cells has been remarkably improved recently: from 10.1% to 11.8%. Front transparent conductive oxide (TCO) films have played an important role in this efficiency improvement. In this study, the impact of the front TCO films was investigated by comparing microcrystalline silicon solar cells with In2O3:Sn films grown by sputtering and ZnO:B films grown by metal-organic chemical vapor deposition (MOCVD). Improvement mechanisms in open-circuit voltages and fill factors in solar cells are investigated and discussed.

The three-dimensional (3D) distribution of nanosized silicon (Si) crystallites within a hydrogenated nanocrystalline Si (nc-Si:H) material is examined by laser-assisted atom probe tomography (APT). The amorphous and crystalline phases in nc-Si:H are distinguished by obtaining the 3D density distribution of H atoms, because the former contains a high H density. The H content in the amorphous phase is estimated to be approximately 15 at% by APT, which is consistent with that obtained by infrared spectroscopy. Thus, the 3D analysis of H distribution via APT is a powerful method to visualize the real shape of nanosized crystallites within nc-Si:H materials.

Laser-assisted atom probe tomography was used to identify the impurity distribution in Si heterojunction (SHJ) solar cells composed of thin doped/intrinsic amorphous Si layers on the textured surface of a crystalline Si wafer. A site-specific lift-out technique involving a focused ion beam enabled the selection of a ?2 × 2 ?m2area on an arbitrary pyramidal surface. The distributions of B, P and C in the amorphous Si layers introduced by p-type (trimethyl-borane or diborane) or n-type (phosphine) dopant gases were investigated. Standard guidelines for the assessment of the H content in amorphous Si of SHJ solar cells were provided.