4 research outputs found
Large-Scale Micro- and Nanopatterns of Cu(In,Ga)Se<sub>2</sub> Thin Film Solar Cells by Mold-Assisted Chemical-Etching Process
A reactive mold-assisted chemical etching (MACE) process through an easy-to-make agarose stamp soaked in bromine methanol etchant to rapidly imprint larger area micro- and nanoarrays on CIGS substrates was demonstrated. Interestingly, by using the agarose stamp during the MACE process with and without additive containing oil and triton, CIGS microdome and microhole arrays can be formed on the CIGS substrate. Detailed formation mechanisms of microstructures and the chemical composition variation after the etching process were investigated. In addition, various microand nanostructures were also demonstrated by this universal approach. The microstructure arrays integrated into standard CIGS solar cells with thinner thickness can still achieve an efficiency of 11.22%, yielding an enhanced efficiency of ∼18% compared with that of their planar counterpart due to an excellent absorption behavior confirmed by the simulation results, which opens up a promising way for the realization of high-efficiency micro- or nanostructured thin-film solar cells. Finally, the complete dissolution of agarose stamp into hot water demonstrates an environmentally friendly method by the mold-assisted chemical etching process through an easy-to-make agarose stamp
Improved Efficiency of a Large-Area Cu(In,Ga)Se<sub>2</sub> Solar Cell by a Nontoxic Hydrogen-Assisted Solid Se Vapor Selenization Process
A nontoxic hydrogen-assisted
solid Se vapor selenization process (HASVS) technique to achieve a
large-area (40 × 30 cm<sup>2</sup>) CuÂ(In,Ga)ÂSe<sub>2</sub> (CIGS)
solar panel with enhanced efficiencies from 7.1 to 10.8% (12.0% for
active area) was demonstrated. The remarkable improvement of efficiency
and fill factor comes from improved open circuit voltage (<i>V</i><sub>oc</sub>) and reduced dark current due to (1) decreased
interface recombination raised from the formation of a widened buried
homojunction with n-type Cd<sub>Cu</sub> participation and (2) enhanced
separation of electron and hole carriers resulting from the accumulation
of Na atoms on the surface of the CIGS film. The effects of microstructural,
compositional, and electrical characteristics with hydrogen-assisted
Se vapor selenization, including interdiffusion of atoms and formation
of buried homojunction, were examined in detail. This methodology
can be also applied to CIS (CuInSe<sub>2</sub>) thin film solar cells
with enhanced efficiencies from 5.3% to 8.5% (9.4% for active area)
and provides a facile approach to improve quality of CIGS and stimulate
the nontoxic progress in the large scale CIGS PV industry
Wafer-Scale Growth of WSe<sub>2</sub> Monolayers Toward Phase-Engineered Hybrid WO<sub><i>x</i></sub>/WSe<sub>2</sub> Films with Sub-ppb NO<sub><i>x</i></sub> Gas Sensing by a Low-Temperature Plasma-Assisted Selenization Process
An
inductively coupled plasma (ICP) process was used to synthesize
transition metal dichalcogenides (TMDs) through a plasma-assisted
selenization process of metal oxide (MO<sub><i>x</i></sub>) at a temperature as low as 250 °C. In comparison with other
CVD processes, the use of ICP facilitates the decomposition of the
precursors at low temperatures. Therefore, the temperature required
for the formation of TMDs can be drastically reduced. WSe<sub>2</sub> was chosen as a model material system due to its technological importance
as a p-type inorganic semiconductor with an excellent hole mobility.
Large-area synthesis of WSe<sub>2</sub> on polyimide (30 × 40
cm<sup>2</sup>) flexible substrates and 8 in. silicon wafers with
good uniformity was demonstrated at the formation temperature of 250
°C confirmed by Raman and X-ray photoelectron (XPS) spectroscopy.
Furthermore, by controlling different H<sub>2</sub>/N<sub>2</sub> ratios,
hybrid WO<sub><i>x</i></sub>/WSe<sub>2</sub> films can be
formed at the formation temperature of 250 °C confirmed by TEM
and XPS. Remarkably, hybrid films composed of partially reduced WO<sub><i>x</i></sub> and small domains of WSe<sub>2</sub> with
a thickness of ∼5 nm show a sensitivity of 20% at 25 ppb at
room temperature, and an estimated detection limit of 0.3 ppb with
a <i>S</i>/<i>N</i> > 10 for the potential
development
of a low-cost plastic/wearable sensor with high sensitivity
Performance Characterization of Dye-Sensitized Photovoltaics under Indoor Lighting
Indoor
utilization of emerging photovoltaics is promising; however,
efficiency characterization under room lighting is challenging. We
report the first round-robin interlaboratory study of performance
measurement for dye-sensitized photovoltaics (cells and mini-modules)
and one silicon solar cell under a fluorescent dim light. Among 15
research groups, the relative deviation in power conversion efficiency
(PCE) of the samples reaches an unprecedented 152%. On the basis of
the comprehensive results, the gap between photometry and radiometry
measurements and the response of devices to the dim illumination are
identified as critical obstacles to the correct PCE. Therefore, we
use an illuminometer as a prime standard with a spectroradiometer
to quantify the intensity of indoor lighting and adopt the reverse-biased
current–voltage (<i>I</i>–<i>V</i>) characteristics as an indicator to qualify the <i>I</i>–<i>V</i> sampling time for dye-sensitized photovoltaics.
The recommendations can brighten the prospects of emerging photovoltaics
for indoor applications