The crystalline silicon heterojunction structure adopted in photovoltaic modules commercialized as Panasonic's HIT has significantly reduced recombination loss, resulting in greater conversion efficiency. The structure of an interdigitated back contact was adopted with our crystalline silicon heterojunction solar cells to reduce optical loss from a front grid electrode, a transparent conducting oxide (TCO) layer, and a-Si:H layers as an approach for exceeding the conversion efficiency of 25%. As a result of the improved short-circuit current (J sc ), we achieved the world's highest efficiency of 25.6% for crystalline silicon-based solar cells under 1-sun illumination (designated area: 143.7 cm 2 ).

The electrical behavior of nitrogen-hydrogen (N-H) complexes and carbon (C) atoms in GaAsN films grown by the chemical beam epitaxy (CBE) method have been studied by comparing H concentrations and hole concentrations. The contributions of H and C concentrations ([H] and [C]) to ionized impurity scattering have been also investigated. In the GaAsN films, there were three acceptor levels (A0, A1, and A2). The energy levels of A1 and A2 were 130 and 55 meV, respectively. The concentration of the deepest acceptor (A0) was more than 10 19 cm À3 , which was higher than [H] and [C]. A2 was observed only in films with a high [C]. The amount of A1 was proportional to [H]. Most of the residual H formed N-H complexes; thus, it is concluded that the N-H complex behaved as an acceptor in GaAsN films. At low temperatures, ionized impurity scattering limited the total hole mobility. The inverse numbers of the coefficients for the ionized scattering were consistent with [C] instead of [H]. This suggests that all the residual C atoms were ionized owing to compensation by the donors. A disagreement between N composition and alloy scattering has been also detected. This might indicate a fluctuation in the N composition in the GaAsN films.

A strong expectation exists for a two-terminal hybrid perovskite/silicon tandem solar cell for generating substantially higher output power. Nevertheless, a high tandem cell efficiency under the standard condition does not guarantee high power generation in outdoor environment due to the requirement of current matching in a tandem device. Here, we predict the global energy yields of hybrid perovskite/Si tandem and Si heterojunction single modules by establishing a new rigorous self-consistent model that performs full device simulations incorporating all fundamental time-varying parameters affecting the module power output. In particular, the temperature dependences of the optical and electrical characteristics are modeled explicitly and reliable model parameters are extracted from an industry-compatible Si heterojunction single cell (23.27% efficiency with a 120 μm wafer thickness), whereas ideal cell characteris-

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 μm2 area 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.

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.