Photovoltaic (PV) modules are generally considered to be the most reliable components of PV systems. The PV module has a high probability of being able to perform adequately for 30 years under typical operating conditions. In order to evaluate the long-term performance of a PV module under diversified terrestrial conditions, outdoor-performance data should be used. However, this requires a wait of 25 years to determine the module reliability, which is highly undesirable. Thus, accelerated-stress tests performed in the laboratory by mimicking different field conditions are important for understanding the performance of a PV module. In this paper, we discuss PV-module degradation types and different accelerated-stress types that are used to evaluate the PV-module reliability and durability for life expectancy before using them in the real field. Finally, prevention and correction measures are described to minimize economic losses.
We have explored the effect of post-annealing on the electrical properties of an indium gallium zinc oxide (IGZO) transistor with an Al
2
O
3
bottom gate dielectric, formed by a sol–gel process. The post-annealed IGZO device demonstrated improved electrical performance in terms of threshold variation, on/off ratio, subthreshold swing, and mobility compared to the non-annealed reference device. Capacitance–voltage measurement confirmed that annealing can lead to enhanced capacitance properties due to reduced charge trapping. Depth profile analysis using X-ray photoelectron spectroscopy proved that percentage of both the oxygen vacancy (V
O
) and the hydroxyl groups (M–OH) within the IGZO/Al
2
O
3
layers, which serve as a charge trapping source, can be substantially reduced by annealing the fabricated transistor device. Furthermore, the undesired degradation of the contact interface between source/drain electrode and the channel, which mainly concerns V
O
, can be largely prevented by post-annealing. Thus, the facile annealing process also improves the electrical bias stress stability. This simple post annealing approach provides a strategy for realising better performance and reliability of the solid sol–gel oxide transistor.
Electronic supplementary material
The online version of this article (10.1186/s40580-019-0194-1) contains supplementary material, which is available to authorized users.
Wide
band gap oxide materials with additional infrared (IR) photosensing
have rarely been reported because of the lack of the IR-associated
sub band gap absorption. In this work, we report that the insertion
of a thin aluminum oxide (Al2O3) layer between
the Al electrode and indium gallium zinc oxide (IGZO) channel, deposited
by atomic layer deposition, enables the material to absorb 850 nm
IR light as well as light at visible wavelengths (400 and 530 nm).
UV–visible absorption and photoluminescence measurements showed
that the Al2O3/IGZO-stacked channel layers could
induce additional IR absorption and, consequently, IR-excited charge
carriers owing to sub-gap doping within the IGZO band gap. Notably,
this approach provides the synergetic effect of enabling IR detection
as well as improving the contact properties in the IGZO transistor.
Furthermore, the clear dynamic photoswitching behavior was observed
only for the Al2O3/IGZO transistor device, revealing
a photocurrent 50 times higher than the device containing only IGZO.
Thus, the simple approach of engineering the interface of wide band
gap oxide materials made it possible to introduce unexpected dual-band
gap photosensing characteristics, thereby extending the range of photonic
applications of these materials.
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