2 research outputs found
High efficiency CdTe solar cells by low temperature deposition with MgZnO HRT layer
CdTe solar cells have shown high efficiency and the technology is scalable. As a result thin film CdTe modules are competitive with crystalline silicon modules. Thin film CdTe devices with efficiency above 22% have been reported using high substrate temperatures during the
deposition process. It is known that high substrate temperatures result in large grain size with a reduced number of grain boundaries and this is believed to contribute to the high efficiency. However, use of high temperature requires robust substrates and excludes the use of most flexible substrate materials. It also involves higher energy consumption and more complicated machinery. In this work we present a process for high efficiency solar cells with an improved front contact, by introducing
magnesium-doped zinc oxide high resistance transparent layer. By optimizing the fabrication process we have achieved a conversion efficiency exceeding 16%, which is one of the highest reported for substrate temperatures
below 500°C
Water (H<sub>2</sub>O and D<sub>2</sub>O) Dispersible NIR-to-NIR Upconverting Yb<sup>3+</sup>/Tm<sup>3+</sup> Doped MF<sub>2</sub> (M = Ca, Sr) Colloids: Influence of the Host Crystal
Tm<sup>3+</sup>/Yb<sup>3+</sup> doped
CaF<sub>2</sub>, SrF<sub>2</sub>, and cubic phase NaYF<sub>4</sub> nanoparticles dispersed
as colloids in water (H<sub>2</sub>O and D<sub>2</sub>O) or saline
solutions have been directly prepared by a one-step hydrothermal technique,
using citrate anions as capping agents, without the need for any postsynthesis
reaction. The size monodispersed nanoparticles are directly dispersed
in water. Comparison of the upconversion emissions at 800 nm (Tm<sup>3+</sup> ions) among the CaF<sub>2</sub>, SrF<sub>2</sub>, and NaYF<sub>4</sub> hosts indicates that the SrF<sub>2</sub> host leads to the
highest emission intensity, 2 orders of magnitude higher than the
NaYF<sub>4</sub> one. Alkali ions (Na<sup>+</sup> or K<sup>+</sup>) counter cations of the citrate salts used as precursors can enter
the fluoride host crystals as charge compensators and strongly influence
the spectroscopic properties of the lanthanide ions. The Tm<sup>3+</sup>/Yb<sup>3+</sup> doped SrF<sub>2</sub> nanoparticles dispersed in
a 0.4 g/L concentration solution show detectable upconversion with
laser excitation intensities as low as 1 W/cm<sup>2</sup>