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Infrared soldering as a step in module encapsulation, which would cause light-induced degradation (LID) and light- and elevated-temperature-induced degradation (LeTID) effects on solar cells, may cause efficiency mixing among solar cells that were originally in the same grade within the module after soldering. Furthermore, the problem of bright and dark regions would appear, which would result in a decrease in the CTM value. Current injection is considered to be one of the effective methods to solve the above problem. However, after the current injection treatment, there is still a 10% probability of the appearance of bright and dark regions in modules. In this work, we first adopted the conventional current injection process in monocrystalline passivated emitter and rear cells (PERCs). The effects of injected currents, temperature and time were systematically optimized, and cells with or without the current injection under the optimal parameters were illuminated with 1 sun at 85 °C for 25 h. Secondly, a piece of equipment was developed to further stabilize the performance of solar cells and improve the CTM value. The results showed that the best current injection parameters were a temperature of 185 °C, an injected current of 11 A and an injection time of 770 s. Compared with the cells without any pretreatment, the relative changes in the η, Voc, Isc and FF of the cells pretreated with the optimal conditions mentioned above were 0.23%, 0.08%, 0.02% and 0.08% larger, respectively, after 25 h of degradation. Then, solar cells processed by current injection were processed with our equipment, and the probability of a problem occurring was reduced from 10% to 2%. Meanwhile, the CTM value increased by 0.4%. Finally, a balance mechanism between H0 and H0-X has been proposed to explain the mechanism of the equipment. [ABSTRACT FROM AUTHOR]

An important challenge in industrial laser ablation is laser-induced damage. In this study, reduced damage was achieved through the transition of the laser distribution from a Gaussian beam to a top-hat beam using diffractive optical elements (DOE), which overcome inhomogeneous irradiation. The higher peak fluence of a Gaussian beam far exceeded the ablation threshold and led to severely melted silicon at a higher depth covering the polished texture. The top-hat beam, with uniform irradiation, had a superior ablation characteristic and created a uniform square opening with the shallow melted silicon in the lift-off process. Thus, its effective minor carrier lifetime was 15.35% less at an ablated area fraction of 2% after re-passivation because of the decreased damage. After optimizing the ablation pattern with a top-hat beam, the local contacts improved the average open-circuit voltage (Voc) and short-circuit current (Isc) values of the cells due to the decreased damage and the uniform openings, but the damage induced by a Gaussian beam was too deep and can be partly restored under back surface field (BSF) formation. The overall increment in Isc and Voc enhanced the average efficiency by 0.05% of the absolute value for the PERC cells and 0.03% of the absolute value for bi-facial PERC cells. [ABSTRACT FROM AUTHOR]

Compared with typical mono-facial photovoltaic (PV) solar modules, bifacial solar modules can make full use of reflected or scattered light from the ground and the surroundings to yield more electrical energy. The electrical energy on the rear side depends on multiple factors, such as the IV parameters of modules, packaging materials, and installation circumstances. In this work, the power generation output is simulated and researched using the PV-SYST software program, based on the different electrical parameters of bifacial solar modules and the installation conditions of the given PV systems. The influencing factors that affect the electrical energy are further analyzed using power-loss diagrams. The results show that improving the surface albedo can raise additional energy by 8.3%, thus behaving significantly better than the mono-facial module. Furthermore, improving the siting height and incidence angle modifier (IAM) of the modules can increase the additional energy by 3.1%. In contrast, adjusting the output current or voltage of the modules adds some energy, while the modules are of the same nominal power value. It was observed that the energy level of a photovoltaic system mainly depends on the installation circumstances, but the electrical parameters of the modules themselves contribute little. [ABSTRACT FROM AUTHOR]

In recent years, polycrystalline passivated emitter and rear cell (PERC) solar cells have developed rapidly, but less research has been conducted on the preparation process of their rear side passivation layers on standard solar cell production lines. In this work, a Al2O3/SiNx rear side stacked passivation layer for polycrystalline PERC solar cells was prepared using the plasma- enhanced chemical vapor deposition (PECVD) method. The effects of different Al2O3 layer thicknesses (6.8~25.6 nm), SiNx layer thicknesses (65~150 nm) and SiNx refractive indices (2.0~2.2) on the passivation effect and electrical performance were systematically investigated, which were adjusted by TMA flow rate, conveyor belt speed and the flow ratio of SiH4 and NH3, respectively. In addition, external quantum efficiency (EQE) and elevated temperature-induced degradation experiments were also carried out to check the cell performance. The results showed that the best passivation effect was achieved at 10.8 nm Al2O3 layer, 120 nm SiNx layer and 2.2 SiNx layer refractive index. Under the optimal conditions mentioned above, the highest efficiency was 19.20%, corresponding Voc was 647 mV, Isc was 9.21 A and FF was 79.18%. Meanwhile, when the refraction index was 2.2, the EQE of the cell in the long-wavelength band (800–1000 nm) was improved. Moreover, the decrease in conversion efficiency after 45 h LeTID was around 0.55% under the different refraction indices. The above results can provide a reference for the industrial production of polycrystalline PERC solar cells. [ABSTRACT FROM AUTHOR]

The absence of an effective texturing technique for diamond-wire sawn multi-crystalline silicon (DWS mc-Si) solar cells has hindered commercial upgrading from traditional multi-wire slurry sawn silicon (MWSS mc-Si) solar cells. In this work, we present a novel method for the removal of diamond-wire-sawn marks in a multi-crystalline silicon wafer based on metal assisted chemical etching process with Cu/Ag dual elements and nano-structure rebuilding (NSR) treatment to make a uniform inverted pyramid textured structure. The temperature effect of NSR solution was systematically analyzed. It was found that the size of the inverted pyramid structure and the reflectance became larger with the increase of the NSR treatment temperature. Furthermore, the prepared unique inverted pyramid structure not only benefited light trapping, but also effectively removed the saw-marks of the wafer at the same time. The highest efficiency of 19.77% was obtained in solar cells with an inverted pyramid structure (edge length of 600 nm) fabricated by NSR treatment at 50 °C for 360 s, while its average reflectance was 16.50% at a 400–900 nm wavelength range. [ABSTRACT FROM AUTHOR]

In this paper, we report one bifacial p-type PERC solar cell with efficiency over 22% using laser doped selective emitter produced in larger-scale commercial line on 6-inch mono-crystalline wafer. On front side of the solar cell, square resistance of p-n junction was found to be closely related with laser power at certain laser scan speed and frequency. On the other side, the rear fingers with different ratios of height and width and rear silicon nitride (SiNx) layer with different thickness were optimized, and a highest rear efficiency of the bifacial solar cell was obtained. Finally, bifacial silicon solar cells with the front and rear efficiencies exceeding 22% and 15% (AM1.5, 1000 W/m2, 25 °C) were successfully achieved, respectively. [ABSTRACT FROM AUTHOR]

Multicrystalline silicon (mc-Si) PERC (passivated emitter and rear cell) solar cells suffer from severe light-induced degradation (LID), which mainly consists of two mechanisms, namely, BO-LID (boron–oxygen complex-related LID) and LeTID (light and elevated temperature induced degradation). The impact of thermal treatment on the LID of a mc-Si PERC solar cell is investigated in this work. The LID of mc-Si PERC solar cells could be alleviated by lowering the peak temperature of thermal treatment (namely sintering), perhaps because fewer impurities present in mc-Si tended to dissolve into interstitial atoms, which have the tendency to form LeTID-related recombination active complexes. The LID could also be effectively restrained by partially replacing the boron dopant with gallium, which is ascribed to the decreased amount of boron–oxygen (B–O) complexes. This work provides a facile way to solve the severe LID problem in mc-Si PERC solar cells in mass production. [ABSTRACT FROM AUTHOR]