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.
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.
We propose a microwave diode based on a modulation-doped GaAs/Al 0.25 Ga 0.75 As structure. The principle of the diode operation relies on a non-uniform heating of the two-dimensional electron gas in microwave electric fields arising due to the asymmetric shape of the device. The voltage sensitivity of the diode at room temperature is close to 0.3 V W −1 at 10 GHz, which is comparable to the value obtained using similarly shaped and sized diodes based on bulk n-GaAs. At liquid nitrogen temperature, the voltage sensitivity strongly increases reaching a value of 20 V W −1 due to the high mobility of the two-dimensional electron gas. The detected signal depends linearly on power over 20 dB, until hot-electron real-space-transfer effects begin to predominate. We discuss noise temperature measurements at 10 GHz, consider the frequency dependence of the voltage sensitivity in the microwave range and compare the performance data of the proposed device and the asymmetrically shaped bulk GaAs diode within the 10 GHz-2.5 THz frequency range.
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