To decouple the trade-off relationship between short-circuit current I SC and open-circuit voltage V OC of thin-film silicon solar cells, which vary with texture morphology, it is necessary to first clarify the relationship between a solar cell's properties and its texture morphology. We have developed a method for quantitatively measuring the texture morphology, which has enabled us to identify novel indices on the basis of texture width and angle individually correlated to I SC and V OC . A texturing process based on these indices should allow I SC and V OC to be improved independently.

We developed a fabrication technique of very thin silicon nanowall structures. The minimum width of the fabricated silicon nanowall structures was about 3 nm. This thinnest region of the silicon nanowall structures was investigated by using cathode luminescence and ultraviolet photoelectron spectroscopy (UPS). The UPS measurements revealed that the density of states (DOS) of the thinnest region showed a stepwise shape which is completely different from that of the bulk Si. Theoretical analysis clearly demonstrated that this change of the DOS shape was due to the quantum size effect.

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-

Wide-gap Si nanowire (SiNW) solar cells that use the quantum size effect require a p–n junction to be formed inside wires with a diameter smaller than 4 nm. To realize this, we developed a device integration process and confirmed power generation, for the first time, by an axial-junction SiNW solar cell with a diameter of 30 nm and a device area of 1 mm2. We confirmed that such a SiNW solar cell had almost the same open-circuit voltage and low short-circuit current density as a bulk Si solar cell. We also investigated the problems related to SiNW solar cells by measuring the functioning SiNW density.