Polymers have traditionally been used for so-called passive applications in many areas of electronics, for instance, as passivation and insulating materials in electronic packaging and as lithograp...

Conjugated and Fullerene-Containing Polymers for Electronic and Photonic Applications: Advanced Syntheses and Microlithographic Fabrications

In the last decade the ns2 cations (e.g., Pb2+ and Sn2+)-based halides have emerged as one of the most exciting new classes of optoelectronic materials, as exemplified by for instance hybrid perovskite solar absorbers. These materials not only exhibit unprecedented performance in some cases, but they also appear to break new ground with their unexpected properties, such as extreme tolerance to defects. However, because of the relatively recent emergence of this class of materials, there remain many yet to be fully explored compounds. Here, we assess a series of bismuth/antimony oxyhalides and chalcohalides using consistent first principles methods to ascertain their properties and obtain trends. Based on these calculations, we identify a subset consisting of three types of compounds that may be promising as solar absorbers, transparent conductors, and radiation detectors. Their electronic structure, connection to the crystal geometry, and impact on band-edge dispersion and carrier effective mass are discussed. Detailed first-principles calculations reveal the potential of bismuth-based and antimony-based chalcohalides and oxyhalides for optoelectronics applications. The presence of ions with outer electron configuration of ns
 2
 in halides has rendered them very promising for applications, like solar cells. In this work, collaborators from Jilin University, University of Missouri, and Arkansas State University have used density functional theory to study the properties of several chalcohalides and oxyhalides containing bismuth or antimony ns
 2
 cations. It turns out that certain bismuth-based chalcohalides are promising for solar cells applications and room-temperature radiation detectors, with bandgaps in the range 1.5–2 eV. Some oxyhalides, on the other hand, with bandgaps above 3 eV are hole-conducting, which makes them suitable for transparent conducting materials, if they can be doped. This work underlines that further experimental work is needed to fully assess the potential of this class of materials for optoelectronics applications.

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Bismuth and antimony-based oxyhalides and chalcohalides as potential optoelectronic materials

Two-dimensional (2D) materials exhibit high sensitivity to structural defects due to the nature of interface-type materials, and the corresponding structural defects can effectively modulate their inherent properties in turn, giving them a wide application range in high-performance and functional devices. 2D γ-Ga2S3 is a defective semiconductor with outstanding optoelectronic properties. However, its controllable preparation has not been implemented yet, which hinders exploring its potential applications. In this work, we introduce nonlayered γ-Ga2S3 into the 2D materials family, which was successfully synthesized via the space-confined chemical vapor deposition method. Its intriguing defective structure are revealed by high-resolution transmission electron microscopy and temperature-dependent cathodoluminescence spectra, which endow the γ-Ga2S3-based device with a broad photoresponse from the ultraviolet to near-infrared region and excellent photoelectric conversion capability. Simultaneously, the device...

Nonlayered Two-Dimensional Defective Semiconductor γ-Ga2S3 toward Broadband Photodetection.

In the last decade the ns$^2$ cations (e.g., Pb$^{2+}$ and Sn$^{2+}$) based halides have emerged as one of the most exciting new classes of optoelectronic materials, as exemplified by for instance hybrid perovskite solar absorbers. These materials not only exhibit unprecedented performance in some cases, but they also appear to break new ground with their unexpected properties, such as extreme tolerance to defects. However, because of the relatively recent emergence of this class of materials, there remain many yet to be fully explored compounds. Here we assess a series of bismuth/antimony oxyhalides and chalcohalides using consistent first principles methods to ascertain their properties and obtain trends. Based on these calculations, we identify a subset consisting of three types of compounds that may be promising as solar absorbers, transparent conductors, and radiation detectors. Their electronic structure, connection to the crystal geometry, and impact on band-edge dispersion and carrier effective mass are discussed.

Bismuth and Antimony Based Oxyhalides and Chalcohalides as Potential Optoelectronic Materials

We investigated an antimony chalcohalide compound, SbSeI, as a potential semiconductor material for X-ray and γ-ray detection. SbSeI has a wide band gap of 1.70 eV with a density of 5.80 g/cm3, and it crystallizes in the orthorhombic Pnma space group with a one-dimensional chain structure comprised of infinite zigzag chains of dimers [Sb2Se4I8]n running along the crystallographic b axis. In this study, we investigate conditions for vertical Bridgman crystal growth using combinations of the peak temperature and temperature gradients as well as translation rate set in a three-zone furnace. SbSeI samples grown at 495 °C peak temperature and 19 °C/cm temperature gradient with 2.5 mm/h translation rate produced a single phase of columnar needlelike crystals aligned along the translational direction of the growth. The ingot sample exhibited an n-type semiconductor with resistivity of ∼108 Ω·cm. Photoconductivity measurements on these specimens allowed us to determine mobility–lifetime (μτ) products for electron...

Photoconductivity in the Chalcohalide Semiconductor, SbSeI: a New Candidate for Hard Radiation Detection

α-Ga2S3 and α-Ga2S3:Fe2+ single crystals were grown by the two-zone sublimation method. The optical energy gaps of α-Ga2S3 and α-Ga2S3:Fe2+ at 10 K were found to be 3.440 and 3.392 eV, respectively. From the absorption spectra of α-Ga2S3:Fe2+, the crystal field parameter Dq of 345 cm−1 and Racah parameters B of 700 and C of 3365 cm−1 were obtained for tetrahedral Fe2+ ions. From the photoluminescence spectra at 10 K, the blue and red emissions at 424 and 643 nm, respectively, for α-Ga2S3 and the violet and yellow emissions at 400 and 580 nm, respectively, for α-Ga2S3:Fe2+ were observed. All the emission lines observed in the photoluminescence spectra were identified.

Blue photoluminescence of α-Ga2S3 and α-Ga2S3:Fe2+ single crystals

Single crystals of ${\mathrm{ZnGa}}_{2}$${\mathrm{Se}}_{4}$:${\mathrm{Co}}^{2+}$ were grown by the chemical transport reaction method. The optical absorption of single crystals was investigated in the temperature range 20\char21{}300 K. The optical-absorption peaks due to the transition $^{4}\mathrm{A}_{2}$${(}^{4}$F)${\ensuremath{\rightarrow}}^{4}$${\mathrm{T}}_{1}$${(}^{4}$P), $^{4}\mathrm{A}_{2}$${(}^{4}$F)${\ensuremath{\rightarrow}}^{4}$${\mathrm{T}}_{1}$${(}^{4}$F), and $^{4}\mathrm{A}_{2}$${(}^{4}$F)${\ensuremath{\rightarrow}}^{4}$${\mathrm{T}}_{2}$${(}^{4}$F) of the ${\mathrm{Co}}^{2+}$ ion that has entered the substitutional tetrahedral sites appeared at 12 830, 6221, and 4000 ${\mathrm{cm}}^{\mathrm{\ensuremath{-}}1}$ at 289 K. The crystal-field parameter and the Racah parameter were given by Dq=400 ${\mathrm{cm}}^{\mathrm{\ensuremath{-}}1}$ and B=469 ${\mathrm{cm}}^{\mathrm{\ensuremath{-}}1}$, respectively. The transition $^{4}\mathrm{A}_{2}$${(}^{4}$F)${\ensuremath{\rightarrow}}^{4}$${\mathrm{T}}_{1}$${(}^{4}$P) split into a triplet state by first-order spin-orbit\char21{}coupling effects in the temperature range 55\char21{}289 K, and the ${\ensuremath{\Gamma}}_{8}$+${\ensuremath{\Gamma}}_{7}$ level split into ${\ensuremath{\Gamma}}_{8}$ and ${\ensuremath{\Gamma}}_{7}$ levels by second-order spin-orbit\char21{}coupling effects of ${\mathrm{Co}}^{2+}$ ions in the low-temperature range below 55 K. The spin-orbit\char21{}coupling parameter was found to be \ensuremath{\lambda}=-363 ${\mathrm{cm}}^{\mathrm{\ensuremath{-}}1}$.

Optical absorption of ZnGa2Se

The optical energy band gaps of BaAl2S4 and BaAl2Se4 single crystals at 300 K were found to be 3.98 and 3.35 eV, respectively, and the optical energy band gaps of Ho3+, Er3+, and Tm3+-doped BaAl2S4 and BaAl2Se4 single crystals were smaller than those of the undoped single crystals. Photoluminescence spectra peaked at 459 and 601 nm in the BaAl2S4 and at 486 and 652 nm in the BaAl2Se4. The photoluminescence emission peaks were attributed to donor–acceptor pair recombinations. Photoluminescence spectra of the Ho3+, Er3+, and Tm3+-doped BaAl2S4 and BaAl2Se4 at 5 K were measured in the wavelength range of 400–900 nm. Sharp emission peaks due to Ho3+, Er3+, and Tm3+ ions were observed and their transition mechanisms were proposed.

Optical properties of undoped and Ho3+, Er3+, and Tm3+-doped BaAl2S4 and BaAl2Se4 single crystals

MgxZn1−xSe single crystals were grown by the closed tube sublimation method. The MgxZn1−xSe single crystals crystallized into zincblende and wurtzite structures in the composition ranges of x=0.0–0.1 and x=0.2–0.6, respectively. Blue and violet emissions with LO phonon replica and self-activated emissions in the MgxZn1−xSe single crystals were observed at 10 K.

Photoluminescence properties of MgxZn1−xSe single crystals

SbSBr, BiSBr, SbSBr:Co and BiSBr:Co single crystals were grown by the Bridgman technique. The grown single crystals crystallize in an orthorhombic structure and have an indirect band structure. The temperature dependence of the optical energy gap for the single crystals shows anomalies at the first and second-order phase transition points. Cobalt dopants are located at the Td symmetry point in the host single crystals as Co2+ and Co3+ ions. Impurity optical absorption peaks due to the electron transitions between the energy levels of the Co2+ and Co3+ ions are observed.

https://iopscience.iop.org/article/10.1088/0268-1242/10/8/021/pdf

Moon-Seog Jin

Papers

Blue photoluminescence of α-Ga2S3 and α-Ga2S3:Fe2+ single crystals

Optical absorption of ZnGa2Se

Optical properties of undoped and Ho3+, Er3+, and Tm3+-doped BaAl2S4 and BaAl2Se4 single crystals

Photoluminescence properties of MgxZn1−xSe single crystals

Optical properties of undoped and Co-doped SbSBr and BiSBr single crystals