New simplified methods for patterning the rear contact of RP-PERC high-efficiency solar cells (original) (raw)
Related papers
Optimization of Rear Local Contacts on High Efficiency PERC Solar Cells Structures
International Journal of Photoenergy, 2013
A local contact formation process and integration scheme have been developed for the fabrication of rear passivated point contact solar cells. Conversion efficiency of 19.6% was achieved using 156 × 156 mm, pseudo square, p-type single crystalline silicon wafers. This is a significant improvement when compared to unpassivated, full area aluminum back surface field solar cells, which exhibit only 18.9% conversion efficiency on the same wafer type. The effect of rear contact formation on cell efficiency was studied as a function of contact area and contact pitch, hence the metallization fraction. Contact shape and the thickness of Al-BSF layer were found to be heavily dependent on the laser ablation pattern and contact area. Simulated cell parameters as a function of metallization showed that there is a tradeoff between open circuit voltage and fill factor gains as the metallization fraction varies. The rear surface was passivated with an Al 2 O 3 layer and a SiN capping layer. The rear surface contact pattern was created by laser ablation and the contact geometry was optimized to obtain voids free contact filling, resulting in a uniform back surface field. The efficiency gain in rear passivated cells over the reference cells is mainly due to improved short circuit current and open circuit voltage.
IEEE Access
A device simulation model for localized contact rear side oxide-passivated solar cell has been developed to study the effects of rear contact coverage and fixed charge density dependent field-effect passivation on the performance of p-Si solar cell. Models describing hetero-interface physics related to metal-semiconductor, metal-oxide-semiconductor junctions and interface recombination are considered in the simulation, results of which are verified with the reported experimental data. A detailed analysis of the effect of surface passivation is presented and an analytical design with optimized set of parameters is outlined for fabricating the cell. The result shows that the efficiency of the solar cell can be substantially enhanced by controlling parameters mainly the ratio between localized back contact to the non-contact area and the fixed charge density at the oxide-interface. A maximum efficiency of ∼25% for a crystalline p-Si solar cell with a comparatively lower lifetime can be obtained by a suitable choice of the design parameters with an added suitable choice of doping concentration in the emitter and absorber and the oxide layer thickness. INDEX TERMS Al 2 O 3 , crystalline silicon, local contact, numerical modeling, solar cell, surface passivation.
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.
Industrial PERL-type solar cells exceeding 19% with screen-printed contacts and homogeneous emitter
Solar Energy Materials and Solar Cells, 2012
Aiming at the development of a cost-effective and industrially up-scalable process for the production of p-Si PERL-type solar cells, this work focuses on the selection and the development of an optimal rearcontacting method of screen-printed aluminum back electrodes through AlO x-based rear passivation stacks. Laser-Fired Contacts are first optimized by developing dedicated characterization protocols to define an optimal laser process. Laser parameters are systematically varied (e.g. pulse energy, power density, focus, and contact pitch) and their effect on the contacts quality is analyzed. Besides, a new contacting method, called Extended-Laser-Ablation (ELA), is presented, allowing even higher efficiencies to be attained thanks to better quality of local back-surface fields. Both contacting routes are then implemented and compared in the PERL pilot production process flow to investigate their effects on cells performances. Top efficiencies of 19.13% (AlO x /SiN x) and 19.5% (SiO 2 /AlO x /SiN x) are reached when the ELA process is used on monocrystalline Cz Si, using a close-to-standard process (75 O/sq homogeneous emitter, screen-printed contacts, standard cleaning procedure), without any final forming gas annealing step required.
Pilot line processing of 18.6% efficient rear surface passivated large area solar cells
2010 35th IEEE Photovoltaic Specialists Conference, 2010
We use the recently introduced Silicon Nitride Thermal Oxidation (SiNTO) process for the industrial fabrication of silicon solar cells that feature a thermal oxide passivated rear surface and local rear contacts. The SiNTO process represents an innovative approach for the fabrication of a passivated emitter and rear cell (PERC), since the front end part from the conventional process sequence is maintained. We apply mostly industrial production equipment using Czochralski silicon wafers that are partly processed in an industrial production line. Conventional screen printing is used for the formation of the front contacts. A stable conversion efficiency of 18.6% (independently confirmed) is achieved for a PERC device fabricated from conventional boron doped Cz-Silicon by means of the SiNTO process. The average efficiency of a batch of 24 SiNTO cells is 18.4%, measured after fabrication (not stabilized). A test module fabricated from 16 SiNTO solar cells features a fill factor of 76.2% and an open circuit voltage of 10.16 V, corresponding to an average of 635 mV per cell.
High-voltage p-type PERC solar cells with anchored plating and hydrogenation
Progress in Photovoltaics: Research and Applications, 2018
A common concern regarding plated contacts to solar cells is the adhesion strength. In this work, laser-formed anchor points have been applied to Suntech Power's PLUTO passivated emitter and rear cells. Voltages as high as 696 mV have been achieved, showing the ability of a laser-doped selective emitter at the front surface and localized contacts at the rear when combined with the hydrogenation of defects to reduce the device dark saturation current to well below current norms for commercial passivated emitter and rear cells. The simple hydrogen passivation process applied during sintering appears to facilitate the high voltages by significantly reducing recombination associated with the p-type Cz wafer and laser-induced defects formed during laser doping. The same hydrogenation process almost entirely eliminates the damage caused by laser ablation in forming the anchor points. With 50% anchor point coverage (more than necessary for adhesion equivalent to or stronger than screen-printed contacts), an average V OC of 693 mV was achieved, with an average current of 40.5 mA/cm 2 , average device efficiency of 20.2%, and a single best cell of 20.5% efficiency. These cells also exhibit excellent contact adhesion and pass all thermal cycling and damp-heat testing according to IEC 61215.
Solar Energy Materials and Solar Cells, 2011
In order to manufacture high-efficiency Si solar cells with a passivated rear surface and local contacts, it is necessary to develop both an excellent rear-passivation scheme compatible with screen-printing technology and a robust patterning technique for local contact formation. In this work, we have fabricated Si solar cells on $ 130 mm thick substrates using manufacturable processing, where rear side was passivated with a plasma-enhanced chemical vapor deposited SiO x /SiN x /SiO x N y stack and local back contacts using laser. As a result of both the rear surface passivation stack and the laser-fired local contacts, cell efficiencies of up to 17.6% on a 148.6 cm 2 Float-zone Si wafer and 17.2% for a 156.8 cm 2 multicrystalline Si wafer were achieved. PC-1D calculations revealed that the cells had a back surface recombination velocity (BSRV) of $ 400 cm/s and a back surface reflectance (BSR) of over 90%, as opposed to standard full Al-BSF cells having a BSRV of $ 800 cm/s and a 70% BSR. This result clearly indicates that the new technique of the passivation scheme and the patterning using laser developed in this study are promising for manufacturing high-efficiency PERC-type thin Si solar cells.
i-PERC technology enables Si solar cell efficiencies beyond 20%
A cost-effective and industrial version of the well-known passivated-emitter and rear cell (PERC) concept has been developed by imec. The imec i-PERC technology comprises a large-area p-type monocrystalline Si solar cell with, on its front, a homogeneous emitter, a thin thermal oxide layer and fine-line Ag screen-printed contacts; on its rear, the cell has a chemically polished surface, low-cost rear dielectric stack layers and local Al contacts. Yielding certified efficiencies of up to 20% and fill factors of 80%, these cells clearly outperform aluminium back-surface field (Al-BSF) cells. During the development stages, process complexity and additional tool investment were kept to a minimum. It is therefore believed that this technology can be picked up by companies in a straightforward way as the next-generation industrial solar cell technology.
15th International Conference on Concentrator Photovoltaic Systems (CPV-15), 2019
In this work, a high voltage, both sides screen-printed n-type passivated emitter and rear totally diffused rear junction (n-PERT-RJ) solar cell concept with Al point contacts on its rear side is proposed. A dash pattern for the firing through Ag contact is applied instead of performing the selective doping on the front surface field (FSF), that effectively reduced the area-weighted metal-induced recombination current J0, Met (Ag). The impact of different n-bulk properties on the n-PERT-RJ solar cell performance is revealed by Quokka3 simulation. An innovative "point-line" concept is then introduced which is composed of dot-shaped laser contact opening (LCO) and Al metal grid, aims to possess bifacial gain in addition to the preservation of high VOC in order to further reduce the levelized cost of energy (LCOE). This industrial type n-PERT-RJ solar cell demonstrates the same performance level as the advanced passivated contact solar cell concepts, the cost of ownership (COO) is close to the p-PERC solar cells, last but not least, shows the performance stability after light and elevated temperature induced degradation (LeTID) tests.