High-efficiency n-type silicon solar cells with front side boron emitter (original) (raw)
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Towards industrial n-type PERT silicon solar cells: rear passivation and metallization scheme
Energy Procedia, 2011
Recently, we presented an industrially feasible passivation and contacting scheme for the front side boron emitter of n-type silicon solar cells based on firing processes. On these cells, efficiencies up to 20.8% have been achieved on small areas. These cells feature a fully-metalized BSF on the rear side, which limits the V OC to about 655 mV. When changing to a PERT cell design with a passivated BSF, both the V OC as well as the J SC can be improved due to a reduced recombination at the rear and an improved optical confinement. In this work we studied different POCl 3 diffusions for their applicability to n-type PERT solar cells with respect to passivation and metallization. The achieved results have been used to fabricate a first batch of n-type PERT solar cells, on which V OC values up to 671 mV have been measured. The improved internal quantum efficiency above 900 nm confirms the improvement of the rear side of the cell. The boron emitter of this cell was passivated with a stack of 5 Å ALD Al 2 O 3 (four ALD cycles) and 70 nm PECVD SiN x . Thus the V OC of 671 mV demonstrates furthermore, that the Al 2 O 3 thickness of fired Al 2 O 3 /SiN x stacks for the passivation of boron emitters can be drastically reduced to four atomic layers of Al 2 O 3 .
Materials research express, 2019
The industrial production of solar cells of the PERC family is growing, because the potential to increase the efficiency due to the passivation of the rear face. The PERT solar cell is a cost-effective structure of the PERC configurations. The goal of this paper is to analyze the influence in the electrical parameters of different metal pastes used to form the contact with the boron back surface field of PERT solar cells passivated with silicon dioxide on both sides and developed with a cost-effective process. The boron doped BSF and phosphorus emitter were carried out with reduction of steps. Solar cells were processed with three different conductive pastes: (1) an aluminum paste (PV381), (2) a silver/aluminum paste (PV3N1) and (3) a silver paste (PV51G), with different viscosity and solids content. The pastes were produced by DuPont. The PV381 and PV3N1 pastes produced solar cells with the efficiency of 16.2% and 15.9%, respectively. The higher open circuit voltage was achieved with the aluminum paste, indicating that this paste is more effective to produce the selective back surface field. The PV51G paste is not suitable to form the rear contact.
physica status solidi (a), 2019
Boron junction and its passivation is an active topic in photovoltaic research due to its importance to passivated emitter and rear totally‐diffused (PERT) bifacial Si solar cell. In this paper, a systematic study on boron‐implanted junction, its passivation and ohmic contact formation, as well as application to p‐PERT bifacial cells has been presented. More specifically, the impact of junction profile and surface passivation on boron junction quality, which can be influenced by implantation and in situ oxidation anneal parameters is studied. Good‐quality boron emitter and metal/p+‐Si ohmic contact are achieved, as demonstrated by emitter saturation current of 5–30 fA cm−2 and specific contact resistance of 3–6 mΩ cm−1. A roadmap for a p‐PERT bifacial cell using fully ion implanted (boron and phosphorus) technology, based on which p‐PERT bifacial cells demonstrats front side efficiency of 20.6% (open circuit voltage of 658 mV), rear side efficiency of ≈17% and bifaciality factor of ...
High efficiency n-type Si solar cells on Al2O3-passivated boron emitters
Applied Physics Letters, 2008
In order to utilize the full potential of solar cells fabricated on n-type silicon, it is necessary to achieve an excellent passivation on B-doped emitters. Experimental studies on test structures and theoretical considerations have shown that a negatively charged dielectric layer would be ideally suited for this purpose. Thus, in this work the negative-charge dielectric Al2O3 was applied as surface passivation layer on high-efficiency n-type silicon solar cells. With this front surface passivation layer, a confirmed conversion efficiency of 23.2% was achieved. For the open-circuit voltage Voc of 703.6mV, the upper limit for the emitter saturation current density J0e, including the metalized area, has been evaluated to be 29fA∕cm2. This clearly shows that an excellent passivation of highly doped p-type c-Si can be obtained at the device level by applying Al2O3.
24% efficient perl silicon solar cell: Recent improvements in high efficiency silicon cell research
Solar Energy Materials and Solar Cells, 1996
Recent research upon high efficiency passivated emitter, rear locally-diffused (PERL) cells has restrlted in a considerable improvement in the energy conversion efficiencies of silicon solar cells up to 24.0% under the standard global solar spectrum. Under monochromatic light, energy conversion efficiency of 46.3% for 1.04 p.m wavelength light has been measured. These efficiencies are the highest ever reported for a silicon device.
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.
Progress in Photovoltaics: Research and Applications, 2014
ABSTRACT In this paper, we evaluate p-type passivated emitter and rear locally diffused (p-PERL) and n-type passivated emitter and rear totally diffused (n-PERT) large area silicon solar cells featuring nickel/copper/silver (Ni/Cu/Ag) plated front side contacts. By using front emitter p-PERL and rear emitter n-PERT, both cell structures can be produced with only a few adaptations in the entire process sequence because both feature the same front side design: homogeneous n+ diffused region with low surface concentration, SiO2/SiNx:H passivation, Ni/Cu/Ag plated contacts. Energy conversion efficiencies up to 20.5% (externally confirmed at FhG-ISE Callab) are presented for both cell structures on large area cells together with power-loss analysis and potential efficiency improvements based on PC1D simulations. We demonstrate that the use of a rear emitter n-PERT cell design with Ni/Cu/Ag plated front side contacts enables to reach open-circuit voltage values up to 676 mV on 1–2 Ω cm n-type CZ Si. We show that rear emitter n-PERT cells present the potential for energy conversion efficiencies above 21.5% together with a strong tolerance to wafer thickness and bulk resistivity. Copyright © 2014 John Wiley & Sons, Ltd.
Industrial PERL-Type Si Solar Cells With Efficiencies Exceeding 19.5%
IEEE Journal of Photovoltaics, 2013
In this paper, we describe a path toward industrial passivated emitter, rear locally diffused (PERL)-type crystalline Si solar cells with efficiencies exceeding 19.5%. The impact of thickness and quality of different local back surface field (BSF) pastes on the extended laser ablation (ELA) rear contacting technique is investigated, and the effect of the wafer resistivity and emitter diffusion/oxidation processes on cell performance is evaluated. Based on these investigations, an optimized process flow for PERLtype monocrystalline Si solar cells is defined, and its capability is tested against that of standard Al-BSF in large batch experiments, demonstrating a top efficiency of 19.7%, a 19.5% average efficiency, and an efficiency increase of about 1% abs. with respect to Al-BSF cells. Index Terms-Crystalline silicon solar cells, light-induced degradation, local back surface field, passivated emitter, rear locally diffused (PERL).
Amorphous silicon passivation applied to the front side boron emitter of n-type silicon solar cells
Hydrogenated amorphous silicon (a-Si:H) was used to passivated the front side boron emitter of n-type silicon solar cells. The main aspect was to investigate the parasitic absorption behavior of the a-Si:H layers on the solar cells front side with different thicknesses between 5 nm and 20 nm. Therefore planar solar cells featuring a diffused boron emitter and a diffused back surface field were fabricated. The cells reached energy conversion efficiencies up to 17.8% with an open- circuit voltage VOC of 641 mV for an a-Si:H thickness of 15 nm. Analogous processed reference cells, with an Al2O3 passivated emitter achieved an efficiency of 19% and a VOC of 658 mV.
Energy Procedia, 2014
We have achieved 21% large-area conversion efficiency with PERL (passivated emitter, rear locally diffused) solar cells featuring plated front contacts. Industrial 156 mm p-type Czochralski single-crystalline silicon wafers were used as substrates. Our cells employ a single-side texture, a single-side emitter, and a double-layer anti-reflective coating composed of PECVD silicon nitride and thermal silicon oxide layers. The rear side is passivated with a dielectric stack (Al 2 O 3-SiO x N y), and the rear contacts are formed through laser-ablated openings by screen-printing and firing an aluminum electrode. The nickel-silver or nickel-copper-silver contacts are plated on the front side by light-induced plating (LIP). The champion batch shows average values of 669 mV open-circuit voltage, 40.0 mA/cm 2 short-circuit current density, and 77.3% fill factor. The efficiency of our PERL cell is currently limited by the series resistance. Implementing small (1-2 μm) and uniform pyramids and thermally annealing the cells after plating show promising results for future improvements.