Towards 20.5% efficiency PERC Cells by improved understanding through simulation (original) (raw)
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New simplified methods for patterning the rear contact of RP-PERC high-efficiency solar cells
2000
New processing schemes for fabricating the rear contact pattern of the PERC-structure (Passivated Emitter and Rear Cell) are demonstrated. Both, thermally-grown silicon oxide (SiO2) and plasmadeposited silicon nitride (SiN,) are used as the passivating rear layer. The first processing scheme utilizes plasma etching of the dielectric layer through a mask. The plasma process was optimized in order to reduce the damage in the silicon base of the cell. Efficiencies of 21.5 % and 21.7 % have been achieved for SIN, and SiO2 rear layers, respectively. The second approach uses a laser beam to remove the dielectric layer for the rear contact pattern. Efficiencies of 19.7 % and 21.3 % have been achieved for SiNx and SiO2 rear layers, respectively. Reference cells with the same front structure but conventionally processed rear (photo resist, wet-chemical etching) show only a slightly higher efficiency of 22.0 % on cells with a SiO2 passivation layer. This proves that both approaches have a very high potential.
Loss analysis and efficiency potential of p-type MWT–PERC solar cells
Solar Energy Materials and Solar Cells, 2012
A loss analysis is carried out for monocrystalline large-area p-type metal wrap through passivated emitter and rear cells (MWT-PERC) with thermal SiO 2 /SiN x surface passivation reaching a maximum conversion efficiency of 20.6 %. Analytical and numerical device modelling identifies the most important loss mechanisms and allows for a separation of the different series resistance contributions and various short circuit current loss mechanisms. Based on the extracted data, an estimation of the possible maximum conversion efficiency for p-type MWT-PERC solar cells is given.
Power-loss Analysis of Advanced PERC Cells Reaching 20.5% Energy Conversion Efficiency
Energy Procedia, 2013
We recently demonstrated at imec a relatively simple process sequence for the formation of copper based front contacts consisting of: i) defining the front contact pattern by laser ablation ii) plating of the contacts using Ni/Cu/Ag f f in a single plating sequence and finally iii) contact sintering. In this paper, we conduct a power loss analysis of the best 20.5% (confirmed by ISE CalLab) PERC solar cell produced on 125 mm magnetically pulled CZ (m-CZ) Si with Ni/Cu/Ag contacts. Based on this power loss analysis, we estimate potential improvements in cell design enabling >21% energy conversion efficiencies.
15th International Conference on Concentrator Photovoltaic Systems (CPV-15)
Three approaches to close the efficiency gap between screen-printed Ag-paste and Ni/Cu/Ag-plated front contact metallization on industrial passivated emitter and rear cells (PERC) solar cells are presented in this paper. In the first approach, the POCl3 diffusion is adjusted to an emitter profile (reduced peak doping) for plated contacts. The second approach is to adapt the laser over doping (LOD) process of the phosphor silicate glass (PSG) to create the selective emitter to the properties of laser patterning and plating. In the third approach, we vary the process step order of front laser patterning and back side aluminum firing. The three approaches show very promising results. Efficiencies higher than 22% and opencircuit voltage VOC values of close to 680 mV are reached on a cell area of 251,99cm². Overall the values excel the reference values obtained with screen printing and firing of Ag-paste. For future developments, VOC values between 685 mV and 690 mV and efficiencies around 22.5% seem very likely.
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.
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.
Impact of the Environmental Effective Albedo on the Performance of PERC + Solar Cells
Silicon, 2020
Owing to a most simple and cost-effective bifacial cell process, the Bifacial PERC + Solar Cells concept has been quickly adopted by various solar cell manufacturers. In this study, we analyze the variation of the PERC + cells performance such as short-circuit current density (J sc), open-circuit voltage (V oc), fill factor (FF) and output power (P out) as a function of real albedos of usual surfaces. The simulation is done with PC2D which is a solar cell device simulator that models two-dimensional effects entirely within a Microsoft Excel spreadsheet and allows us to model bifacial cells with illumination of both surfaces simultaneously. So, the simulator can model the equivalent characteristic J-V of the PERC + cells. The results showed us a significant increase in the performance of the PERC + cells; the output power can achieve 35.56 mW/cm 2 for the snow. Also the study showed a very good linearity of the four parameters (J sc ,V oc , FF, P out) with the effective albedo. Therefore, we can predict these parameters for other effective albedos of current surfaces without simulating the PERC + cell.
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.
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.