Realization of Thin MC-Silicon Pert-Type Bifacial Solar Cells in Industrial Environments (original) (raw)
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The high efficiency solar cells, like buried contact solar cells, often require a dense silicon nitride as a diffusion barrier and anti reflection coating. This is normally realized by Low Pressure Chemical Vapour Deposition (LPCVD) using dichloro silane based nitride deposited at temperatures in the range of 700°C-800°C. In this work we present bifacial solar cells with front side buried contact and rear side screen printed, realized using a lower temperature LPCVD process based on bis-(tertiary butyl amino)-silane (BTBAS) precursor. The temperature used for the nitride deposition is in the range of 550°C to 600°C. The solar cells produced show fill factors over 77.6% on the front side and 76.8% on the rear side. This higher fill factor values indicates that this hybrid contact structure works well for the bifacial solar cell structure. In addition the cell structure has better mechanical strength as compared to double side buried contact solar cell.
Bifacial Solar Cells on Multi-Crystalline Silicon with Boron BSF and Open Rear Contact
2006 IEEE 4th World Conference on Photovoltaic Energy Conference, 2006
The standard industrial multi-crystalline silicon (mc-Si) solar cell is monofacial and includes screen printed aluminum back surface field (BSF). A simple approach to increase performance and reduce costs per Wpeak is to collect the albedo on the rear side. In this work a bifacial, screen printed mc-Si solar cell with boron BSF is demonstrated. Rear to front efficiency ratios of up to 0.83 have been reached on 100x100mm² mc-Si wafers with a thickness of about 200mm. The best solar cell processed so far with a boron BSF had an efficiency under front side illumination of h=16.1% and a back to front efficiency ratio of 0.77. The possible gain in performance in later operation was estimated using PC1D simulation and depends on the albedo that is the amount of light that penetrates into the solar cell from the rear side. The simulation was confirmed by outside module tests, leading to an average gain of 19.5% over one day.
Analysis of thin bifacial silicon solar cells with locally diffused and selective back surface field
Materials Research, 2014
The aim of this work is to present the development and comparison of thin n + pp + industrial bifacial silicon solar cells produced with the local screen-printed Al back surface field (BSF) to those with the selective BSF doped with aluminum-boron. To produce solar cells with selective BSF, the boron diffusion based on spin-on dopant was introduced in the process sequence. The thin SiO 2 layer (10 nm) thermally grown did not produce good passivation on the rear face and wafers were contaminated during aluminum diffusion in the belt furnace. The implementation of selectively doped BSF improved the efficiency by reflecting minority charge carriers and the wafer contamination by belt furnace was compensated by boron diffusion. The bifacial solar cells with B-Al selective BSF achieved an efficiency of 13.7% / 8.9% (front / rear illumination) and presented lower sensitivity to the belt furnace processing and to the quality of the rear surface passivation.
High Efficiency Fully Implanted and Co-annealed Bifacial N-type Solar Cells
Energy Procedia, 2013
The aim of the study was to develop a very simple process for the fabrication of large area n-type PERT cells by means of ion implantation. We showed an improvement of the implanted boron activation rate with the annealing temperature by comparing boron SIMS and ECV concentration profiles. A direct positive impact on the boron emitter saturation current density (J 0e ) was measured. We also investigated the effect of varying the oxidation conditions during the annealing on the implanted boron emitter and the phosphorus BSF quality. Low emitter saturation current density (J 0e ) of 131 fA/cm 2 was measured on textured surfaces, close to the value obtained with diffused B-emitters. A process flow was developed leading to an average efficiency of 19% on 239 cm 2 bifacial solar cells, using only eight processing steps with two implantations and one activation annealing.
A Novel Low-Cost Method for Fabricating Bifacial Solar Cells
Conference Record of the IEEE Photovoltaic Specialists Conference
In this work we propose and demonstrate a novel and cost-effective method to fabricate bifacial cells with conventional homojunction architecture. The method combines benefits of lithography-less, self-aligned patterning during deposition of antireflective coating (ARC) and simultaneous metallization of both surfaces aided by electroplating. We have fabricated a conventional diffused n + pp + junction bifacial solar cell on a monocrystalline silicon (c-Si) substrate using this method. Electrochemically grown nickel is used to simultaneously form front and back electrodes. The bifacial solar cell fabricated with an un-optimized process has a front and rear efficiencies (under AM1.5G one sun illumination) of 12% and 8.66%, respectively. Part of the low performance of the cell is attributed to poor quality of the passivation layer and the post deposition annealing to reduce pinholes in deposited SiN x layer to prevent parasitic plating.
High efficiency screen printed bifacial solar cells on monocrystalline CZ silicon
We present industrialized bifacial solar cells on large area (149 cm 2 ) 2 cm CZ monocrystalline silicon wafers processed with industrially relevant techniques such as liquid source BBr 3 and POCl 3 open-tube furnace diffusions, plasma enhanced chemical vapor deposition (PECVD) SiN x deposition, and screen printed contacts. The fundamental analysis of the paste using at boron-diffused surface and the bifacial solar cell firing cycle has been investigated. The resulting solar cells have front and rear efficiencies of 16.6 and 12.8%, respectively. The ratio of the rear J SC to front J SC is 76.8%. It increases the bifacial power by 15.4% over a conventional solar cell at 20% of 1-sun rear illumination, which equals to the power of a conventional solar cell with 19.2% efficiency. We also present a bifacial glass-glass photovoltaic (PV) module with 30 bifacial cells with the electrical characteristics.
Energy Procedia, 2015
We have achieved 21.2% efficiency, and 670 mV open-circuit voltage(calibrated in Fraunhofer ISE) of n-type rear junction(RJ) PERT (Passivated Emitter Rear Totally-diffused) solar cell with plated Ni/Ag contacts, Al 2 O 3 rear passivation, and screen-printed local Al BSF on industrial 180μm-thickness 6-inch n-type Czochralski (Cz) single crystalline silicon wafer. Also 21.0% efficiency and 669 mV open-circuit voltages was achieved with 125μm-thickness wafer. Effects of borosilicateglass (BSG) deposited by APCVD in different B 2 H 6 gas flow rate and the influence of O 2 addition during furnace tube anneal were studied in terms of not only boron emitter quality but also impact on the cell Voc and FF. We found that, at fixed diffusion temperature, surface boron concentration could be controlled mainly by changing B 2 H 6 flow rate during BSG deposition by APCVD and subsidiary by O 2 addition in the tube furnace anneal. Additionally, as risks of n-type mass production, the 6" n-type wafer quality deviation issue and thin wafer related process issues were discussed.
Experimental investigation and characterization of innovative bifacial silicon solar cells
International Journal of Renewable Energy Research, 2019
The interest towards bifacial PV technology has increased over the last years, due to its potential capability of obtaining higher efficiencies with respect to traditional monofacial cells. Thus, the aim of this work is to present an experimental investigation on an innovative photovoltaic technology, such as the bifacial solar cells based on monocrystalline substrate. This analysis is mainly based on the determination of the current density/voltage, power density/voltage, External Quantum Efficiency (EQE) and Laser Beam Induced Current (LBIC) characterization. Interesting results are presented and discussed, demonstrating that the bifacial silicon solar cells can be a very promising technology with high electrical performances and efficiency.
20th EPSEC, 2005
The shortage of the p-type silicon (Si) feedstock and the high minority carrier lifetimes in multicrystalline (mc) n-type Si reported by different authors ([1]-[3]) make n-type mc-Si solar cell fabrication more and more interesting. Given the high electronic quality of the material-that is confirmed in our studies again-the task remains to develop an adapted solar cell process. A key feature of the concept presented here is the BBr3diffused emitter on the front side and the surface passivation of this emitter. We show that BBr3 emitter-diffusion is possible without degradation of the high initial carrier lifetimes in the n-type mc-Si material-on contrary the diffusion even improves the average lifetime to a large extend. SiO2 provides an excellent surface passivation of the p +-Si surface. Application of PECVD SiNx resulted in a decrease of the (implied) Voc measured on lifetime teststructures as well as on solar cell level. As an alternative, a low temperature surface passivation process by PECVD SiCx is investigated. First trials resulted in a very promising value for the emitter saturation current Joe: 180 fA/cm 2 for a 90 Ω/sq emitter. N-type Si solar cells with SiO2-passivated BBr3-emitter were processed in laboratory scale (area of 4 cm 2) with an efficiency of 15.2% on mc and 16.4% on Cz-Si. With an industrial screen printing process 14.1% and 14.8% were obtained on an area of 12.5 x 12.5 cm 2 on n-type mc-Si and Cz-Si respectively.
High efficiency on boron emitter n-type Cz silicon bifacial cells with industrial process
N-type Si solar cells arrest comprehensively attention due to the possibility to achieve high and stabilized cell efficiencies without light-induced degradation compared to p-type cells. Meanwhile, the rapid fall in photovoltaic prices drives researchers to continue developing multifarious technology about efficiency improvement and cost reduction in the manufacture of solar cell process. In this article we introduce large area bifacial solar cells on n-type silicon using only industrial facilities. The boron emitter was formed by diffusion technique with BCl3 precursor and the phosphorus BSF was made by ion-implantation followed by in-situ front and back passivation with dry oxide. The resulting cell efficiency achieved 19.7% on 156PSQ Cz wafers and zero LID had been proved after 72 h exposure at 50°C under AM1.5G illumination. In addition, 3.03% of cell to module loss has to be investigated with 36pcs n-bifacial cells built by normal front glass and transparent backsheet.