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In this work, boron paste was coated on the silicon surface by spin-coating method, and the boron-doped emitter and phosphorus-doped back surface field were fabricated in one co-diffusion process, because the boron paste acted as a barrier during phosphorus diffusion. Then, n-PERT (Passivated Emitter Rear Totally-diffused cell) solar cells were successfully prepared by this B/P co-diffusion method with the front efficiency of 20.41% and the back efficiency reaching 18.32%. It was demonstrated that the emitter and back surface field formed a good passivation layer on top by thermal oxidation respectively, which enabled open-circuit voltage to reach 648.7 mV. It should be emphasized that the whole process was effectively simplified compared with the conventional process of n-PERT solar cells. Thus, these first results indicate that B/P co-diffusion might be a promising alternative method for mass production of the n-PERT solar cells. g

In the photovoltaic industry, an antireflection coating consisting of three SiNx layers with different refractive indexes is generally adopted to reduce the reflectance and raise the efficiency of monocrystalline silicon PERC (passivated emitter and rear cell) solar cells. However, for SiNx, a refractive index as low as about 1.40 cannot be achieved, which is the optimal value for the third layer of a triple-layer antireflection coating. Therefore, in this report the third layer is replaced by SiOx, which possesses a more appropriate refractive index of 1.46, it and can be easily integrated into the SiNx deposition process with the plasma-enhanced chemical vapor deposition (PECVD) method. Through simulation and analysis with SunSolve, three different thicknesses were selected to construct the SiOx third layer. The replacement of 15 nm SiNx with 30 nm SiOx as the third layer of antireflection coating can bring about an efficiency gain of 0.15%, which originates from the reflectance reduction and spectral response enhancement below about 550 nm wavelength. However, because the EVA encapsulation material of the solar module absorbs light in short wavelengths, the spectral response advantage of solar cells with 30 nm SiOx is partially covered up, resulting in a slightly lower cell-to-module (CTM) ratio and an output power gain of only 0.9 W for solar module.

PERC solar cell passivated on the backside with AlOx and SiNx was introduced to construct the perovskite/silicon four-terminal tandem solar cell, because of its outstanding spectral response at the long wavelength region and much lower cost than SHJ and IBC. Different from the vast majority of the related reports, which were focused on the improvement of perovskite top cell, the silicon bottom cell was optimized here to promote the tandem efficiency. The central wavelength of antireflection was adjusted to further reduce the reflectance and enhance the spectral response of PERC cell in long wavelengths, in order to make the most of long-wavelength light transmitted through the perovskite top cell. Along with the increase of central wavelength, the external quantum efficiency of PERC cell at near-infrared wavelengths increases resulting in better short circuit current density and photoelectric conversion efficiency when filtered by the perovskite cell. A tandem efficiency gain of 0.07% (abs.) has been achieved. This report provides a facile way to improve the efficiency of perovskite/silicon four-terminal tandem solar cell based on the optimization of long-wavelength spectral response.

In recent years, high-efficiency solar cells have a strong competitiveness in the market and the p-type PERC solar cell is the mainstream product of leading cell manufacturers. To further improve the efficiency and reduce the cost, laser doping selective emitter (LDSE) has been introduced into the mass production line as a promising technology. In this work, we fabricated high efficiency PERC solar cells by using LDSE technique. Firstly, we adjusted the diffusion process and obtained the best sheet resistance (115 ± 5 Ω/sq), which resulted in an efficiency gain of 0.11%. Subsequently, the best diffusion profile of the selective emitter was obtained through optimization. With the surface concentration of about 3.0×1020 atoms/cm3 and emitter depth of 0.32 µm, the optimum photovoltaic parameter gains have been achieved, namely 0.18% for Eff, 6.7 mV for Voc and 0.25 mA/cm2 for Jsc respectively. EQE measurements show that the spectral response can be improved in the short wavelengths through introducing LDSE structure. Correscan measurements indicate that the front contact resistance of SE solar cell was slightly higher than that of reference due to the lateral transport resistance. The efficiency of LDSE solar cell can be increased further by the optimization of laser uniformity and the alignment of screen-printed finger with heavily doped region.

In this work, the industrial glass-glass module was developed using bifacial n-type solar cell. The passivation emitter and rear total diffusion cells (PERT) structure solar cell combined boron spin-on with POCl3 diffusion and double sides H-pattern screen printing metallization. With the assistance of the spin-on single side doping method, an average efficiency of 20% with 90% bifaciality was obtained in our laboratory, 6*10 cells bifacial glass-glass modules were fabricated in industrial line. The PID about 3.5% was obtained after 600 hrs under 85°C-85% humidity with a bias of -1000 V, while the LID was about 0.19% under the IEC standard of 60 kW·h/m2 illumination. As expected, power output gains of 15% on sand and 30% on snow were recorded for the glass-glass bifacial modules compared with mono-facial modules in our outdoor experiments.