A solar-pumped laser (SPL) that converts sunlight directly into a coherent and intense laser beam generally requires a large concentrating lens and precise solar tracking, thereby limiting its potential utility. Here, we demonstrate a fully-planar SPL without a lens or solar tracking. A Nd³⁺-doped silica fiber is coiled into a cylindrical chamber filled with a sensitizer solution, which acts as a luminescent solar collector. The body of the chamber is highly reflective while the top window is a dichroic mirror that transmits incoming sunlight and traps the fluorescence emitted by the sensitizer. The laser-oscillation threshold was reached at a natural sunlight illumination of 60% on the top window. Calculations indicated that a solar-to-laser power-conversion efficiency could eventually reach 8%. Such an SPL has potential applications in long-term renewable-energy storage or decentralised power supplies for electric vehicles and Internet-of-Things devices.

For modeling the energy generation of three-dimensional car roof photovoltaic (PV) panels, it is essential to define a scientifically accurate method to model the amount of solar irradiance received by the panel. Additionally, the average annual irradiance incident on car roofs must be evaluated, because the PV module is often shaded during driving and when parked. The curve-correction factor, which is a unique value depending on the three-dimensional curved shape of the PV module, is defined in this paper. The curve-correction factor was calculated using a ray-trace simulator. It was found that the shape of the curved surface affected the curve-correction factor. The ratio of the projection area to the curved surface area of most car roofs is 0.85–0.95, and the annual curve-correction factor lies between 0.70 and 0.90. The annual irradiance incident on car roofs was evaluated using a mobile multipyranometer array system for one year (September 2017–August 2018). It is estimated that the effective annual solar radiation for curved PV modules is 2.53–3.52 kWh m⁻²/day.

Acceptor doping CdTe with group-V elements is promising for increasing the power conversion efficiency of CdTe photovoltaic devices via an increased hole concentration and open circuit voltage (V_OC). In past work, we have investigated doping with As in Cd-rich CdTe single crystals grown using the Cd-solvent traveling heater method we have developed. In this study, we compare the doping parameters and stability of hole concentration in the light and dark for P, As, and Sb dopants in crystals cooled very slowly from the growth temperature to approximate thermal equilibrium. In contrast to older reports of a high acceptor ionization energy for Sb, our temperature dependent Hall effect experiments reveal an acceptor ionization energy slightly above 90 meV for Sb doping in the mid 10¹⁶ cm⁻³ range. Room temperature hole concentrations above 10¹⁶ cm⁻³ are observed for P, As, and Sb with each dopant type exhibiting only small changes in hole concentrations over 2 years' time at room temperature. Crystals doped with P, As, or Sb exhibit increased conductivity after above-gap illumination, which decays over periods of minutes to hours depending on temperature. Analysis of the photoconductivity decay reveals a barrier attributed to hole capture of 190–280 meV for the series P, As, and Sb.

We demonstrate an extremely low-concentrated solar-pumped laser (SPL) using a fiber laser with transverse excitation geometry. A low concentration factor is highly desired in SPLs to eliminate the need for precise solar tracking and to considerably increase the practical applications of SPL technology. In this Letter, we have exploited the intrinsic low-loss property of silica fibers to compensate for the extremely low gain coefficient of the weakly pumped active medium. A 40 m long ${\mathrm{Nd}}^{3+}$-doped fiber coil is packed in a ring-shaped chamber filled with a sensitizer solution. We demonstrated a lasing threshold that is 15 times the concentration of natural sunlight and two orders of magnitude smaller than those of conventional SPLs.