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.

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The screen-printing process for making good contact of electrodes with the top layer of solar cells is crucial for enhancing the electrical properties of a solar cell. This paper reports the experimental approach adopted for the process of electrode formation and the resulting shape of electrodes in silicon-based heterojunction (SHJ) solar cells. It was observed that good contact between electrodes and the top transparent conductive oxide (TCO) layer strongly depends on the squeegee pressure, curing temperature, and curing time. By optimizing the squeegee pressure at 0.350 MPa, snap-off distance of 1.4 mm, squeegee speed of 80 mm/sec, curing temperature of 180°C, and curing time of 30 minutes, the height to width ratio (aspect ratio) of the fabricated electrodes was achieved at ~0.66. The results have been verified through 3D laser profiler, field emission scanning electron microscopy, transfer length method, and light current-voltage measurements. The SHJ solar cells were fabricated using an optimized condition and successfully achieved splendid properties of short circuit current density (Jsc), open circuit voltage (Voc), fill factor (FF), and efficiency (η) up to 40.57 mA/cm2, 723 mV, 81.03%, and 23.79%, respectively.

The main drawbacks of modern solar-cell technologies are low-quality surface passivation, recombination losses, and carrier selectivity, which limit their efficiency. Therefore, this study proposes an innovative universal approach for a doublebarrier two-dimensional (2D) quantum well (QW) passivation structure for solar cells. To this end, c-Si solar cells were examined as model cells. Preliminary investigations (e.g., contact resistance, passivation, and recombination current density) were conducted with a stack of SiO x /nc-Si/SiO x QW on n-type surfaces, and excellent results were obtained with a 30 nm-thick nc-SiO x (n) carrier-selective layer. Furthermore, the effects of different QW thicknesses and doping doses on the surface passivation of such contacts were studied, and the best results were achieved for a 5 nm QW. These QWs also exhibited a low degree of dopant diffusion, which was suppressed by the double SiO x layer. Furthermore, the 2D QW passivation structure with carrier-selective layers, which was denoted as a heterojunction with quantum well (HQW) solar cell, exhibited an excellent passivation improvement and had a lifetime (τ eff ) of 2746 μs and an implied open-circuit voltage (iV oc ) of 736 mV for a 5 nm 2D QW structure. Moreover, a fabricated 5 nm 2D QW-based silicon heterojunction (SHJ) solar cell exhibited an open-circuit voltage (V oc ) of 732.5 mV, a short-circuit current density (J sc ) of 39.5 mA/cm 2 , a fill factor (FF) of 77.95%, and an efficiency (E ff ) of 22.55%. To validate these findings, theoretical calculations were performed using the experimental results, which confirmed the resonance tunneling of charge carriers across the 5 nm HWQ structure.

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