In this paper, CaGa2S4:3%Nd,5%Yb; CaGa2S4:5%Yb; CaGa2S4:3%Nd compounds were synthesized, and their photoluminescence (PL) spectra, PL excitation (PLE) spectra and PL decay properties were studied at room temperature under one-photon and multi-photon excitation in a wide range of excitation intensities. The synthesis of the CaGa2S4 compound was carried out by a solid-phase reaction of a stoichiometric mixture of CaS and Ga2S3 powders in a quartz ampoule. Yb and Nd doping was carried out during the synthesis process using YbF3 and NdF3. PLE spectra were studied in the wavelength range from 250 to 850 nm, and PL spectra in the range of 400-1500 nm. It has been shown that after introducing Yb3+ ions into thiogallate crystals with Nd3+ ions, a new band near 488 nm is formed and the PL intensity increases by 1-2 orders of magnitude. The anti-Stokes PL spectra of CaGa2S4: Nd, Yb crystals in the visible region of the spectrum (400-700 nm) were studied when excited by continuous wave laser radiation with a wavelength of 975 nm. The kinetics of PL decay of all types of compounds at different wavelengths of single- and multi-photon excitation were determined. Depending on the PLE conditions, wavelength and intensity of the exciting radiation, monoexponential and non-monoexponential decay kinetics were observed with decay times in the range of 20-90 mu s. Possible mechanisms of PLE and PL of CaGa2S4 crystals doped with neodymium and ytterbium ions are discussed.

A study was carried out on the luminescence excitation spectra and photoluminescence (PL) spectra as well as the luminescence kinetics of low-density polyethylene composites with different contents of CaGa2S4:Eu2+ phosphor filler. The phospholuminescence was attributed to the 4f65d → 4f7 transition of the Eu3+ ion and was greatest when the filler concentration was 7 vol.

The effect of irradiation with different doses of 4-MeV electrons on radiative recombination of nonequilibrium charge carriers in Cu(In,Ga)(S,Se)2 thin films of solar cells was studied. Near-edge photoluminescence (PL) in the energy range 0.9–1.2 eV in nonirradiated and irradiated direct-gap Cu(In,Ga)(S,Se)2 solid solutions was caused by optical interband transitions and radiative recombination through energy levels of acceptor- and donor-type structure defects in the presence of strong potential fluctuations. PL spectra measured in the temperature range 5–300 K exhibited energy shifts of the near-edge PL band maxima and redistributions of their intensities in thin films after irradiation with different doses of electrons. The activation energies of nonradiative recombination were determined from the quenching of PL band intensities. The possible nature of structural defects in nonirradiated and electron-irradiated Cu(In,Ga)(S,Se)2 solid solutions was discussed.

Cu2ZnGeS4 single crystals were grown by chemical vapor transport reaction method. Their composition and crystal structure were determined. It was shown that the obtained single crystals crystallize in a tetragonal structure. The band gap of the obtained single crystals was determined basing on transmission spectrum in the region of the absorption edge in temperature range of 10-320 K. It was found that band gap width increases with decreasing of temperature. Keywords: Bridgman method, single crystals, crystal structure, transmission spectrum, band gap.

Методом химических газотранспортных реакций выращены монокристаллы соединения Cu2ZnGeS4. Определен их состав и кристаллическая структура. Показано, что выращенные монокристаллы кристаллизуются в тетрагональной структуре. По спектрам пропускания в области края собственного поглощения в интервале температур 10-320 K определена ширина запрещенной зоны указанных монокристаллов. Установлено, что ширина запрещенной зоны с понижением температуры возрастает. Ключевые слова: монокристаллы, кристаллическая структура, спектры пропускания, ширина запрещенной зоны.

Представлены результаты исследования спектров излучения кристаллов и тонких пленок CuInSe 2 при непрерывном (2 Вт/см 2 ) и наносекундном импульсном лазерном возбуждении в диапазоне плотности мощности возбуждения ~1–100 кВт/см 2 и температурах 10–160 К. Обнаружено, что в кристаллах CuInSe 2 стимулированное излучение возникает в спектральной области 1,033 эВ с минимальным уровнем пороговой накачки 9,8 кВт/см 2 , а при уровнях накачки 36–76 кВт/см 2 наблюдается лазерное излучение. Установлено, что для тонких пленок CuInSe 2 , сформированных на стеклянных подложках с предварительно осажденным на стекло слоем молибдена (структура CuInSe 2 /Mo/стекло), характерно появление только стимулированного излучения в области энергий 1,014–1,097 эВ с минимальным уровнем пороговой накачки 30 кВт/см 2 при температуре 10 К. Обсуждаются механизмы возникновения стимулированного и лазерного излучения в соединении CuInSe 2 .

Spontaneous and stimulated emission (SE) of thin Cu(In,Ga)Se 2 films, deposited on sodium-containing glass substrates and irradiated by protons with an energy of 2.5 keV and doses of 10 14 –10 17 cm –2 , were investigated upon excitation by nanosecond laser pulses with the power density from 5 to 100 kW/cm 2 . An increase in the intensity and a decrease in the SE appearance threshold were found for the films irradiated by protons with doses of 10 14 –10 15 cm –2 , in comparison with nonirradiated films. An increase in the SE threshold and a decrease in the intensity of SE and spontaneous emission were observed at the irradiation dose of 10 16 cm –2 . After a dose of 10 17 cm –2 the intensity of emission decreased sharply and the SE threshold was not reached. Possible reasons of the observed effects are discussed.

Excitonic quality CuInSe 2 crystals were studied using low-temperature (10 K) photoluminescence (PL) excited by continuous wave and nano-second pulsed lasers at power densities from 0.01 to 76kW/cm 2 . Increasing the excitation power density level to 26 kW/cm 2 resulted in the appearance of a stimulated emission SE-band in the PL spectra at 1.035eV. Further increase in the excitation level to 39kW/cm 2 generated on the top of the SE band, a structure of equidistant sharp lines attributed to laser emission.

The emission spectra of thin nanocrystalline films of Cu(In 1 – x Ga x )(S y Se 1 – y ) 2 (CIGSSe) direct-gap solid solutions in the structure of solar cells, recorded upon continuous-wave laser excitation (~0.5 W/cm 2 ) and nanosecond pulsed laser excitation with a power density in the range of 0.1–53 kW/cm 2 at temperatures ranging from 10 to 300 K, are analyzed. It is found that stimulated emission (SE) occurs in thin CIGSSe films at temperatures from 10 to 90 K in the spectral range h ν = 1.062–1.081 eV, with a minimum threshold-pump level of ~1 kW/cm 2 . It is shown that the spontaneous emission band is blue-shifted with an increase in the excitation intensity. It is also established that, with an increase in temperature, the photoluminescence (PL) band (upon weak excitation) and the stimulated-emission band are blue-shifted, whereas the PL band is red-shifted upon strong excitation. The possible reasons and mechanisms for the influence of temperature and excitation intensity on the spectral positions of the spontaneous and stimulated emission bands for the solid-solution films are discussed.

Mn 1.5 AgIn 8.0 S 14 single crystals were grown by the Bridgman directed melt crystallization method. Crystals composition and structure were determined. It was found that these single crystals crystallize in a cubic spinel structure with a lattice constant a = 10.765 ± 0.005 A. The width of the band gap of Mn 1.5 AgIn 8.0 S 14 single crystals was estimated from the transmission spectra in the region of the edge of its intrinsic absorption in the temperature range of 10—320 K. The band gap width decreases with the temperature increasing and a functional approximation of this dependence was obtained.

Spontaneous and stimulated emission (SE) of thin Cu(In,Ga)Se 2 films, deposited on sodium-containing glass substrates and irradiated by protons with an energy of 2.5 keV and doses of 10 14 —10 17 cm -2 , were investigated upon excitation by nanosecond laser pulses with the power density from 5 to 100 kW/cm 2 . An increase in the intensity and a decrease in the SE threshold appearance were found for the films, irradiated by protons with doses of 10 14 —10 15 cm -2 , in comparison with non-irradiated films. An increase in the SE threshold and a decrease in the intensity of SE and spontaneous emission were observed at the irradiation dose of 10 16 cm -2 . After a dose of 10 17 cm -2 the intensity of emission decreased sharply and the SE threshold was not reached. Possible reasons of the observed effects are discussed.

Mn0.3Ag0.7In4.1S6.8 single crystals were grown by directed melt crystallization. Their composition and crystal structure were determined. It was established that the Mn0.3Ag0.7In4.1S6.8 single crystals crystallized in the cubic spinel structure. The band gap of the single crystals was estimated and its temperature dependence was constructed using transmission spectra in the region of the fundamental absorption edge in the range 20–320 K. The temperature dependence of the band gap was shown to have the form characteristic of semiconductor materials.

Mn1.5AgIn8.0S14 single crystals were grown by Bridgman directed melt crystallization. Their composition and crystal structure were determined. Single crystals crystallized in the cubic spinel structure with lattice constant a = 10.765 ± 0.005 Å. The band-gap width of Mn1.5AgIn8.0S14 single crystals was estimated from transmission spectra near the intrinsic absorption edge in the temperature range 10–320 K and decreased with increasing temperature. A function approximating this dependence was obtained.

Mn 0.3 Ag 0.7 In 4.1 S 6.8 single crystals were grown by directed melt crystallization, their composition and crystal structure were determined. It was established that the single crystals Mn 0.3 Ag 0.7 In 4.1 S 6.8 crystallize in a cubic spinel structure. The band gap of the single crystals was estimated from the transmission spectra in the region of the fundamental absorption edge in the temperature range of 20–320 K, and its temperature dependence was constructed. It was shown that the temperature dependence of the band gap has the form characteristic for semiconductor materials.

The emission spectra of thin nanocrystalline films of Cu(In1 – xGax)(SySe1 – y)2 (CIGSSe) direct-gap solid solutions in the structure of solar cells, recorded upon continuous-wave laser excitation (~0.5 W/cm2) and nanosecond pulsed laser excitation with a power density in the range of 0.1–53 kW/cm2 at temperatures ranging from 10 to 300 K, are analyzed. It is found that stimulated emission (SE) occurs in thin CIGSSe films at temperatures from 10 to 90 K in the spectral range hν = 1.062–1.081 eV, with a minimum threshold-pump level of ~1 kW/cm2. It is shown that the spontaneous emission band is blue-shifted with an increase in the excitation intensity. It is also established that, with an increase in temperature, the photoluminescence (PL) band (upon weak excitation) and the stimulated-emission band are blue-shifted, whereas the PL band is red-shifted upon strong excitation. The possible reasons and mechanisms for the influence of temperature and excitation intensity on the spectral positions of the spontaneous and stimulated emission bands for the solid-solution films are discussed.

The results of a study of the emission spectra of thin nanocrystalline films of Cu(In1-xGax)(SySe1-y)2 (CIGSSe) direct-band-gap solid solutions in the structure of solar cells at ~ 0.5 W/cm2 continuous wave and nanosecond pulsed laser excitation in the range of excitation power density 0.1 - 53 kW/cm2 and temperatures of 10-300 K are presented. It was found that stimulated emission (SE) occurs in thin CIGSSe films in the temperature range from 10 K to 90 K in the spectral region h = 1.062 - 1.081 eV with a minimum threshold pump level of about 1 kW/cm2. It was shown, that, with increasing intensity of the exciting emission, the spontaneous emission bands shift toward higher energies. It was found that the photoluminescence bands at low excitation levels and the SE bands shift with increasing temperature toward higher energies, and the PL bands at high excitation levels shift toward low energies. Possible causes and mechanisms of the influence of temperature and excitation intensity on the spectral positions of spontaneous and SE of the films of solid solutions are discussed.

MnAgIn7S12 single crystals 16 mm in diameter and ~40 mm in length are grown by planar crystallization of the melt. It is shown that the material grown crystallizes with the formation of the cubic spinel structure. From the transmittance spectra recorded in the region of fundamental absorption in the temperature range 10–320 K, the band gap Eg of the single crystals and its temperature dependence are determined. The dependence has a shape typical of most semiconductor materials: as the temperature is lowered, the band gap Eg increases. A calculation is carried out, and it is shown that the calculated values are in agreement with the experimental data.

Вертикальным методом Бриджмена выращены монокристаллы AgIn8S12.5. Методом рентгеноспектрального анализа определен состав полученных монокристаллов, методом рентгеновской дифракции --- кристаллическая структура. Показано, что выращенные монокристаллы кристаллизуются в кубической структуре шпинели. По спектрам пропускания в интервале температур 10-320 K определена ширина запрещенной зоны, которая с понижением температуры возрастает. Ключевые слова: метод Бриджмена, монокристаллы, кристаллическая структура, спектры пропускания, ширина запрещенной зоны.

Stimulated emission, optical properties, and structural characteristics of non-irradiated and proton-irradiated Cu(In,Ga)Se2 thin films deposited on soda lime glass substrates using co-evaporation of elements in a multistage process were investigated. X-ray diffraction analysis, scanning electron microscopy, X-ray spectral analysis with energy dispersion, low-temperature photoluminescence, optical transmittance and reflectance were used to study the films. Stimulated emission at low temperatures of ~20 K was found in non-irradiated and proton-irradiated Cu(In,Ga)Se2 thin films upon excitation by laser pulses of nanosecond duration with a threshold power density of ~20 kW/cm2. It was shown that the appearance and parameters of the stimulated emission depend strongly on the concentration of ion-induced defects in Cu(In,Ga)Se2 thin films.