Ion-implanted and screen-printed large area 20% efficient N-type front junction Si solar cells (original) (raw)
Related papers
2014
In this study, we present fully ion-implanted screenprinted high-efficiency 239 cm 2 n-type silicon solar cells that are fabricated on pseudosquare Czochralski wafers. Implanted boron emitter and phosphorous back-surface field (BSF) were optimized to produce n-type front junction cells with front and back SiO 2 /SiN x surface passivation and rear point contacts. Average efficiency of 19.8%, with the best efficiency of 20.2%, certified by Fraunhofer ISE, Freiburg, Germany, was achieved. In addition, the planarized rear side gave better surface passivation, in combination with optimized BSF profile, raised the average efficiency to ∼20% for the fully implanted and screen-printed n-type passivated emitter, rear totally diffused cells.
Progress in Photovoltaics: Research and Applications, 2014
In this paper, we report on commercially viable screen printing (SP) technology to form boron emitters. A screenprinted boron emitter and ion-implanted phosphorus back surface field were formed simultaneously by a co-annealing process. Front and back surfaces were passivated by chemically grown oxide capped with plasma-enhanced chemical vapor deposition silicon nitride stack. Front and back contacts were formed by traditional SP and firing processes with silver/aluminum grid on front and local silver back contacts on the rear. This resulted in 19.6% efficient large area (239 cm 2) n-type solar cells with an open-circuit voltage V oc of 645 mV, short-circuit current density J sc of 38.6 mA/cm 2 , and fill factor of 78.6%. This demonstrates the potential of this novel technology for production of low-cost highefficiency n-type silicon solar cells.
2010 35th IEEE Photovoltaic Specialists Conference, 2010
In this work we combine the firing stable Al2O3 passivation of a boron emitter with an industrially feasible contacting technology to gain a complete front side concept of n-type silicon solar cells with a front side junction. The contact scheme consists of a fine-line printed seed layer, using a silver ink, which is subsequently fired and plated. We studied the contact formation of the applied seed layer on a shallow, industrial-type boron emitter by measuring the specific contact resistance for different firing processes. To gain a deeper insight into the contact formation, SEM micrographs were made from the contact interface. Moreover, the emitter shunting has been studied by firing p + nn + test structures at temperatures between 700 and 850 °C.
High Efficiency on Boron Emitter n-Type Cz Silicon Solar Cells With Industrial Process
IEEE Journal of Photovoltaics, 2011
In this study, we describe the fabrication of n-type solar cells using an industrial process. The open-circuit voltage limitation is discussed by investigating the influence of the screenprinted metallization at the front and rear sides. Efficiencies above 19.0% were obtained on 125PSQ Cz-Si wafers with a reference process. Narrow front metalized fingers were deposited by means of a stencil screen associated with a silver-plating step. Recombination below the contacts due to a metal area reduction resulted in a V o c improvement up to 5 mV. The process flow was then modified to develop an improved back-surface field (BSF).
High-Throughput Ion-Implantation for Low-Cost High-Efficiency Silicon Solar Cells
Energy Procedia, 2012
This paper presents the use of ion-implantation for high-volume manufacturing of silicon solar cells. Ion-implantation provides a unique opportunity to obtain grid-parity because it simplifies the fabrication of advanced cell structures. It is shown in production that a streamlined ion-implantation process with homogeneous phosphorus doped emitter can raise the efficiency of 239 cm 2 p-base Cz cells by 0.8 % absolute, from 18.3 % to 19.1 %, while reducing the process sequence by one step relative to traditional POCl 3 process. Average production cell efficiency is about 18.6 % with maximum exceeding 19 %. Several advanced cell structures were fabricated in R&D using ion-implantation and screen printed contacts. The advanced p-base structure with ion implanted selective emitter and local Al-BSF resulted in an efficiency of 19.6 %. In addition, three different n-base cell structures were fabricated using boron (B) and phosphorus (P) implantation followed by in-situ front and back passivation during the implant anneal: the n-base cell with B emitter, passivated P-BSF with local contact and full metal back gave 19.2 % efficiency, the implanted n-base bifacial cell was 19 % efficient, and the n-base back junction cell with B emitter in the rear and P front surface field resulted in 19 % efficiency.
IEEE Journal of Photovoltaics, 2011
This paper describes the cell design and technology on large-area (239 cm 2) commercial grade Czochralski Si wafers using industrially feasible oxide/nitride rear passivation and screenprinted local back contacts. A combination of optimized front and back dielectrics, rear surface finish, oxide thickness, fixed oxide charge, and interface quality provided effective surface passivation without parasitic shunting. Increasing the rear oxide thickness from 40 to 90Å in conjunction with reducing the surface roughness from 1.3 to 0.2 μm increased the V o c from 640 mV to 656 mV. Compared with 18.6% full aluminum back surface field (Al-BSF) reference cell, local back-surface field (LBSF) improved the back surface reflectance (BSR) from 65% to 93% and lowered the back surface recombination velocity (BSRV) from 310 to 130 cm/s. Twodimensional computer simulations were performed to optimize the size, shape, and spacing of LBSF regions to obtain good fill factor (FF). Model calculations show that 20% efficiency cells can be achieved with further optimization of local Al-BSF cell structure and improved screen-printed contacts.
Solar Energy Materials and Solar Cells, 2018
In this paper n-type PERT (Passivated Emitter and Rear Totally diffused) silicon wafer solar cells with a diffused boron rear emitter and an implanted phosphorus front surface field are investigated. A key feature of the n-PERT rear emitter cell is that it uses the same sequence of surface passivation, rear local laser ablation and screenprinting processes as a commercial p-type PERC (Passivated Emitter and Rear Contact) cell. Therefore, this cell structure is very industrially relevant as it could simplify a production line upgrade from p-type cells to n-type cells. Additionally, ion implantation provides an elegant single-side doping process that further simplifies the processing sequence of n-PERT cells. Ion implantation also provides excellent control over the doping profile via a variation of post-implant annealing time. The effect of annealing time on the implanted phosphorus surface was evaluated in this study in terms of the front surface field dopant profile and its impact on the solar cells' electrical characteristics. A shallower front surface doping profile resulted in better short wavelength response. Additionally, the performance of two different Al pastes (with and without Si content in the paste) was compared. The better-performing Al-Si paste generates a homogeneous Al-p + region under the contacts, which reduces the recombination at the contacts. By tailoring the phosphorus front surface field profiles and by minimising the recombination during the rear Al contact formation, efficiencies of up to 21% on large area 244 cm 2 n-type wafers were achieved so far.
High efficiency industrial screen printed n-type solar cells with front boron emitter
2008 33rd IEEE Photovolatic Specialists Conference, 2008
We have developed a process to fabricate n-type solar cells on large area (156.25 cm 2 ) multicrystalline substrates involving simultaneous diffusion of phosphorous back surface field and boron emitter, screen-printed metallization and firing through SiN x , which leads to a record high efficiency of 16.4%. We apply a simple and costeffective method to passivate industrially produced boron-doped emitters for n-type solar cells with a demonstrated efficiency enhancement of more than 2% absolute. Moreover, it is experimentally demonstrated that the optimum base resistivity for n-type multicrystalline silicon wafers lies between 1.5 to 4 Ωcm. This is a significant step forward for industrial production of solar cells based on n-type mc-Si.
2006 IEEE 4th World Conference on Photovoltaic Energy Conference, 2006
In this paper we present n-type Si solar cells on large area mc-Si wafers with a boron diffused emitter at the front side. The focus of our studies is mainly related to the front surface of the solar cell. We have optimised BBr3-diffusion and in-situ oxidation with respect to the homogeneity of the sheet resistance and substrate degradation. After diffusion even a slight improvement of the minority charge carrier lifetime was measured, which can be related to Bgettering. The emitter is contacted by AgAl-paste and passivated by thermal SiO2. The development and optimisation of all processes led to solar cells with efficiencies of 14.7% on mc-Si and 17.1% on Cz-Si substrates.