Oxygen-Induced Defect-Healing and Photo-Brightening of Halide Perovskite Semiconductors: Science and Application

Solution-processed metal halide perovskite (MHP) semiconductors, have exhibited remarkable success in diverse optoelectronic device applications, especially in solar cells, despite having non-negligible density of defect states. The photoluminescence quantum yield...

Density of Defect States and Spectra of Defect Absorption in a-Si:H

Spectral characteristics of the coefficient of defect absorption in amorphous hydrogenated silicon have been studied. The characteristics are determined, by analyzing the electron transitions occurring with the participation of the energy states of dangling bonds. It is shown that the principal role in the formation of the defect absorption coefficient value is played by the electron transitions between defect and non-localized states. It is also shown that the spectral characteristics are mainly determined by the distribution function of the electron density of states in the valence or conduction band. It is found that the maxima in the spectrum of the defect absorption coefficient are observed only if there are pronounced maxima in the density of states at the edges of allowed bands.

Formation, Structure and Optical Properties of Nanocrystalline BaSi2 Films on Si(111) Substrate

BaSi2 thin films were formed on Si (111) substrate by solid-phase epitaxy (SPE) (UHV deposition) using the template technology followed by vacuum annealing at temperatures of 600 °C and 750 °C. After the deposition and annealing barium silicide films were characterized by Auger electron spectroscopy, grazing incidence x-ray diffraction (GIXRD) and atomic-force microscopy (AFM). It was established that the films annealed at T = 600 °C are polycrystalline with the structure of the orthorhombic BaSi2, with grain sizes of 100-200 nm. Higher anneal temperature (T=750 °C) leads to increase of diffraction peak intensity of BaSi2 phase with grain coagulation into 300-400 nm islands. It was confirmed that nanocrystalline BaSi2 films are characterized by a direct fundamental interband transition at 1.3 eV, the second interband transition with an energy of 2.0 eV, own phonon structure with wave number peaks at 112, 119, 146 and 208 cm-1 and a high density of defect states within the band gap, which provide a noticeable subband absorption at energies of 0.8 – 1.1 eV.

Capacitance Analysis of the Structures with the a-Si:H(i)/c-Si(p) Heterojunction for Solar-Cell Applications

In this paper we present the capacitance study of the intrinsic amorphous silicon/crystalline silicon heterostructure with the aim to gain insight on the heterointerface properties of a passivated silicon heterojunction solar cell. It is shown that due to the high density of defect states in the amorphous layer the structure has to be analyzed as a heterojunction. Using the analysis, the following values have been determined: conduction-band offset of 0.13 eV, electron affinity of 3.92 eV, and density of defect states in the intrinsic amorphous silicon being that of 4.14 X 1021m—3.