Cesium-containing triple cation perovskites are attracting significant attention as suitable tandem partners for silicon solar cells. The perovskite layer of a solar cell must strongly absorb the visible light and be transparent to the infrared light. Optical transmittance measurements of perovskite layers containing different cesium concentrations (0–15%) were carried out on purpose to evaluate the utility of the layers for the fabrication of monolithic perovskite/silicon tandem solar cells. The transmittance of the layers weakly depended on cesium concentration in the infrared spectral range, and it was more than 0.55 at 997 nm wavelength. It was found that perovskite solar cells containing 10% of cesium concentration show maximum power conversion efficiency.

Performance of a perovskite solar cell is largely influenced by the optoelectronic properties of metal halide perovskite films. Here we study the influence of cesium concentration on morphology, crystal structure, photoluminescence and optical properties of the triple cation perovskite film. Incorporation of small amount (x = 0.1) of cesium cations into Cs_x(MA_0.17FA_0.83)_1−x Pb(I_0.83Br_0.17)₃ leads to enhanced power conversion efficiency (PCE) of the solar cell resulting mainly from significant rise of the short-current density and the fill factor value. Further increase of Cs concentration (x > 0.1) decreases the film’s phase purity, carrier lifetime and correspondingly reduces PCE of the solar cell. Higher concentration of Cs (x ≥ 0.2) causes phase segregation of the perovskite alongside with formation of Cs-rich regions impeding light absorption.

The photovoltaic effect in a GaAs p-n junction exposed to short laser pulses of the 1.06–3.0 μm spectral range is investigated experimentally. At a low excitation level of 1.06 μm radiation, the intraband single photon absorption of light dominates, and the photoresponse is found to be caused mainly by the hot carriers. As the laser intensity is increased, the photoresponse signal across the junction consists of two components; the hot carrier photovoltage and the classical photovoltage due to electron-hole pair generation resulting from two-photon absorption. The generation-induced photovoltage decreases with the increase in the radiation wavelength following the reduction of the two-photon absorption coefficient, while the carriers are shown to be heated by the intraband light absorption as well as by residual photon energy left over during the electron-hole pair generation. It is established that carrier heating by light reduces conversion efficiency of a solar cell not only via the thermalization process but also due to the competition of the hot carrier and the classical photovoltages which are of opposite polarities.

The high efficiency of perovskite solar cells strongly depends on the quality of perovskite films and carrier extraction layers. Here, we present the results of an investigation of the photoelectric properties of solar cells based on perovskite films grown on compact and mesoporous titanium dioxide layers. Kinetics of charge carrier transport and their extraction in triple-cation perovskite solar cells were studied by using transient photovoltage and time-resolved photoluminescence decay measurements. X-ray diffraction analysis revealed that the crystallinity of the perovskite films grown on mesoporous titanium dioxide is better compared to the films grown on compact TiO₂. Mesoporous structured perovskite solar cells are found to have higher power conversion efficiency mainly due to enlarged perovskite/mesoporous -TiO₂ interfacial area and better crystallinity of their perovskite films.

In this paper, we propose a novel concept for a semiconductor planar detector. At room temperature, the diode exhibits markedly high responsivity and strong spectral dependence of it: the responsivity value around 2000 V/W is inherent in K _¿ microwave frequency range, and while going up to frequency range D, it decreases by about two orders. Rectification of microwave currents and intervalley electromotive force are discussed to be mainly responsible for high responsivity and its rapid decrease within microwave range. Nevertheless, experiments at higher radiation frequencies performed under the action of pulsed CO₂ laser radiation reveal the planar diode as a fast IR detector and a promising candidate for terahertz radiation sensing.

We propose a new design microwave radiation sensor based on a selectively doped semiconductor structure of asymmetrical shape (so-called bow-tie diode). The novelty of the design comes down to the gating of the active layer of the diode above different regions of the two-dimensional electron channel. The gate influences the sensing properties of the bow-tie diode depending on the nature of voltage detected across the ungated one as well as on the location of the gate in regard to the diode contacts. When the gate is located by the wide contact, the voltage sensitivity increases ten times as compared to the case of the ungated diode, and the detected voltage holds the same polarity of the thermoelectric electromotive force of hot electrons in an asymmetrically shaped n-n⁺ junction. Another remarkable effect of the gate placed by the wide contact is weak dependence of the detected voltage on frequency which makes such a microwave diode to be a proper candidate for the detection of electromagnetic radiation in the microwave and sub-terahertz frequency range. When the gate is situated beside the narrow contact, the two orders of sensitivity magnitude increase are valid in the microwaves but the voltage sensitivity is strongly frequency-dependent for higher frequencies.