Publications Search Results

Now showing 1 - 10 of 71
  • Publication
    TOPCon Silicon Solar Cells with Selectively Doped PECVD Layers Realized by Inkjet-Printing of Phosphorus Dopant Sources
    ( 2022)
    Kiaee, Z.
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    Fellmeth, T.
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    Steinhauser, B.
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    Reichel, C.
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    Nazarzadeh, M.
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    Nölken, A.-C.
    ;
    Keding, R.
    In this article, we evaluate an industrially relevant alternative for the formation of selectively doped n-type tunnel oxide passivating contacts (n-TOPCon) by means of inkjet-printing with the goal to provide a low contact resistance as well as fulfilling the requirements for screen-printing metallization. It is shown that inkjet-printing of phosphorus dopant sources for thick TOPCon layers deposited by plasma-enhanced chemical vapor deposition provides excellent surface passivation with the implied open-circuit voltage iVoc = 733 mV, implied fill factor iFF = 87%, and a high dopant concentration of Npoly-Si ⼠2 à 1020 as required to achieve low contact resistivities when using screen-printed pastes as contacting material. The Voc values of the prepared TOPCon solar cells of 697 mV confirm that the inks and inkjet processes are suitable for integration in TOPCon solar cells. Moreover, these cells enable promising conversion efficiencies of up to ηbest = 22.0% and o ffer a valuable set-up for further investigations on the correlations between inkjet processing and solar cell performance.
  • Publication
    Thermal Laser Separation of PERC and SHJ Solar Cells
    ( 2021)
    Baliozian, P.
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    Münzer, A.
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    Lohmüller, E.
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    Nair, A.
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    Fellmeth, T.
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    Wöhrle, N.
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    Höffler, H.
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    Spribille, A.
    ;
    Preu, R.
    This article investigates thermal laser separation (TLS) on p-type Czochralski-grown silicon (Cz-Si) passivated emitter and rear cells (PERC) and n-type Cz-Si heterojunction (SHJ) solar cells. The TLS comprises of two laser-based processes: the crack initiation by a scribe laser and the crack propagation by a cleave process leading to separated cells with smooth edge surfaces. The sole impact of the cleave process on the cells' passivation layers is examined by performing it without the initial scribe, not separating the samples. By means of photoluminescence imaging, different cleave laser powers PC on passivated PERC and SHJ cell precursors are investigated, and the optimum PC values are then chosen for the processing of metallized and fired host cells with half cell and shingle cell layouts. Both, the cleave process as well as the complete TLS process are then separately performed in order to investigate the effect of each individual process by SunsVOC measurements taken before and after processing. For monofacial PERC cells, a drop in pseudofill factor DpFF = - 0.3%abs is recorded after TLS of the host cell into five shingle cells with 31.35 mm cell width. The effect on bifacial SHJ cells is stronger with DpFF = - 2.1%abs. Thereby, the cleave process itself does not induce significant losses in the cell performance for both cell types. The main losses are attributed to the recombination at the newly created unpassivated edges after complete TLS.
  • Publication
    A Round Robin-Highliting on the Passivating Contact Technology
    ( 2021)
    Fellmeth, T.
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    Feldmann, F.
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    Steinhauser, B.
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    Nagel, H.
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    Mack, S.
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    Hermle, M.
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    Torregrosa, F.
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    Ingenito, A.
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    Haug, F.-J.
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    Morisset, A.
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    Buchholz, F.
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    Chaudhary, A.
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    Desrues, T.
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    Haase, F.
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    Min, B.
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    Peibst, R.
    ;
    Tous, L.
    The aim of this work is to demonstrate the maturity of the TOPCon technology by conducting a round-robin on symmetrically processed lifetime samples in the leading European PV institutes EPFL, ISC, CEA-INES, ISFH, IMEC and Fraunhofer ISE within the H2020 funded project called HighLite. For all layers, dark saturation current-densities ranging between 2 and 10 fA/cm2 can be reported. Simultaneously, no metal induced recombination for the two lower sintering temperatures have been observed pointing towards a true passivated contact. Furthermore, contact resistivities below 10 mOcm2 have been achieved. It seems that the industrial passivating contact matured to a fully passivated and conducting contact enabling full efficiency potential. The fact that this can be realized using either PECVD or LPCVD from various manufacturer is expected to drive costs down and contribute to the increased adoption of the TOPCon technology.
  • Publication
    Laser Assisted Separation Processes for Bifacial pSPEER Shingle Solar Cells
    ( 2020)
    Münzer, A.
    ;
    Baliozian, P.
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    Ahmed, K.
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    Nair, A.
    ;
    Lohmüller, E.
    ;
    Fellmeth, T.
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    Spribille, A.
    ;
    Preu, R.
    In this paper, two laser-assisted separation processes (i) laser scribe and mechanical cleaving (LSMC) and (ii) thermal laser separation (TLS) for the separation of p-type silicon shingled passivated edge, emitter and rear (pSPEER) solar cells are examined. Both separation processes involve two process steps, where one of them is considered the main laser process that is conducted along the whole separation path (laser scribe for LSMC and laser cleave for TLS). We analyze the influence of the main laser process as well as the complete separation process of both, LSMC and TLS, on the electrical performance of pSPEER solar cells. We include an investigation of the dependency on the separation side, i.e. emitter (front side) or emitter-free side (rear side). It is found that by conducting the LSMC process from the front side, a significantly lower energy conversion efficiency by = -1.9%abs in comparison to the rear side process is observed which originates in particular from a lower pseudo fill factor pFF = -7.5%abs. This is attributed to local ablation of the p-n-junction leading to increased j02-like recombination. By conducting the laser scribe without subsequent mechanical cleaving of host cells, we measure pFF = -9.1%abs in comparison to the initial host cell measurement. This indicates that the laser ablation process itself leads to the strong pFF and losses observed after LSMC separation of pSPEER cells. In comparison, the TLS process is found to be invariant to the processed cell side. It is shown that in this case, the involved laser cleave process itself has no measurable impact on the performance of unseparated host cells.
  • Publication
    Post-Metallization Passivated Edge Technology (PET) for Bifacial Silicon Shingle Solar Cells - pSPEERPET
    ( 2020)
    Baliozian, P.
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    Lohmüller, E.
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    Fellmeth, T.
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    Richter, A.
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    Münzer, A.
    ;
    Bhandary, A.
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    Wöhrle, N.
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    Spribille, A.
    ;
    Preu, R.
    We present results in post-metallization ""passivated edge technology"" (PET) and its application on bifacial p-type silicon shingle solar cells. Host cells (full cells with shingle metallization layout after contact firing) separated by either thermal laser separation (TLS) or conventional laser scribe and mechanical cleave (LSMC) show similar drops in pseudo fill factor pFF of -1.2 % abs , After PET, the TLS-separated cells regain 50 % rel of the pFF-drop, i.e. ApFF = +0.6 % abs , while the LSMC-separated ones regain 17 % rel in pFF after PET, i.e. ApFF = +0.2 % abs . Bifacial shingle solar cells processed with TLS and PET attain a peak designated area output power density of 23.5 mW/cm 2 that is 0.4 mW/cm 2 higher than a LSMC-separated shingle cell without PET (considering 100 W/ m2 irradiance from the rear side). The PET leads to improved cell results after separation into shingle cells. The edge passivation is most effective when applied on cells with TLS-separated and thus smooth edges.
  • Publication
    TOPCon Solar Cells: Laser Ablation and Contact Formation Strategies
    ( 2020)
    Arya, V.
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    Schellinger, S.
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    Fellmeth, T.
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    Steinhauser, B.
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    Gruebel, B.
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    Brand, A.
    A comprehensive approach towards metallization of TOPCon cells is undertaken. Conventional screen printing, standard lasered Ni-Cu plated contacts and combination of laser with screen printing approaches are compared and evaluated in terms of increase of recombination current (Dj 0 ) and contact resistivity (p c ). Screen printed contact's resistivity, both with and without laser ablation, fired at 840°C stabilize between 2 - 4 mOcm 2. In comparison, the electroplated contacts reach resistivity levels as low as 0.2 ± 0.1 mOcm 2. Non-lasered contacts display minimal to nil increase in recombination, where as the lasered contacts exhibit an increased recombination current in range of 10 - 20 fA /cm 2.
  • Publication
    Postmetallization "Passivated Edge Technology" for Separated Silicon Solar Cells
    ( 2020)
    Baliozian, P.
    ;
    Al-Akash, M.
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    Lohmüller, E.
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    Richter, A.
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    Fellmeth, T.
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    Münzer, A.
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    Wöhrle, N.
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    Saint-Cast, P.
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    Stolzenburg, H.
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    Spribille, A.
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    Preu, R.
    This article introduces a postmetallization ""passivated edge technology"" (PET) treatment for separated silicon solar cells consisting of aluminum oxide deposition with subsequent annealing. We present our work on bifacial shingle solar cells that are based on the passivated emitter and rear cell concept. To separate the shingle devices after metallization and firing, we use either a conventional laser scribing mechanical cleaving (LSMC) process or a thermal laser separation (TLS) process. Both separation processes show similar pseudo fill factor (pFF) drops of − 1.2% abs from the host wafer to the separated state. The pFF of the TLS-separated cells increases by up to +0.7% abs from the as-separated state after PET treatment due to edge passivation, while the pFF of LSMC-separated cells increases by up to +0.3% abs . On cell level, the combination of TLS and PET allows for a designated area output power density of p out = 23.5 mW/cm², taking into account an additional 10% rear side irradiance.
  • Publication
    Intense pulsed light in back end processing of solar cells with passivating contacts based on amorphous or polycrystalline silicon layers
    ( 2020)
    Schube, J.
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    Tutsch, L.
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    Fellmeth, T.
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    Feldmann, F.
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    Weil, M.
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    Harter, A.
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    Polzin, J.-I.
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    Bivour, M.
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    Keding, R.
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    Glunz, S.W.
    Intense pulsed light (IPL) is capable of entirely replacing thermal annealing (curing and contact formation) within back end processing of silicon solar cells with passivating contacts. In order to demonstrate this, full-size silicon heterojunction (SHJ) cells with IPL-processed screen-printed metal contacts are fabricated. The device with the highest conversion efficiency reaches 23.0%, which is confirmed by Fraunhofer ISE CalLab. On average, IPL-annealed SHJ cells outperform their thermally treated pendants by 0.3-0.4%abs, in particular due to higher open-circuit voltages and fill factors. To further exploit the potential of IPL, it is applied to tunnel oxide passivating contacts (TOPCon). 2 cm × 2 cm-sized p-type solar cells with TOPCon layers on both sides are fabricated. On the front they exhibit indium tin oxide (ITO) layers as well as screen-printed metal contacts which are either thermally or IPL-annealed. The trade-off between low contact resistivity at the TOPCon/ITO interface and high-quality surface passivation (open-circuit voltages of up to 709.4 mV) is balanced, which is a current challenge for the optimization of such devices. The IPL-processed cells' series resistances do not differ significantly from those of thermally treated ones. Due to the pulse durations of several milliseconds only, IPL is very fast and offers a high throughput and, therefore, cost saving potential.
  • Publication
    BBr3 Diffusion: Process Optimization for High-Quality Emitters with Industrial Cycle Times
    ( 2020)
    Lohmüller, E.
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    Glatz, M.
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    Lohmüller, S.
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    Belledin, U.
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    Mack, S.
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    Fellmeth, T.
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    Naber, R.C.G.
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    Wolf, A.
    We demonstrate tube furnace BBr3 diffusion processes for the formation of high-quality homogeneous boron emitters with industrial cycle times of around 2 hours. They feature emitter dark saturation current densities as low as 17 fA/cm² for textured surfaces at a sheet resistance of about 150 O/sq. In order to achieve the respective doping profiles with a maximum charge carrier concentration slightly above 1019 cm-3 and profile depths of about 800 nm, we optimize the atmospheric pressure BBr3 diffusion such that we make use of an increased maximum temperature (below 1000°C) that yields accelerated diffusion of boron atoms. In addition, careful parameter adjustment assures that the total boron doping dose in the silicon is maintained, despite the temperature increase. This optimization shows a great potential in reducing cycle times without compromising the quality of the formed boron emitters and their respective doping profiles.
  • Publication
    Intense Pulsed Light in Back End Processing of Silicon Heterojunction Solar Cells
    ( 2020)
    Schube, J.
    ;
    Fellmeth, T.
    ;
    Weil, M.
    ;
    Nold, S.
    ;
    Keding, R.
    ;
    Glunz, S.W.
    Intense pulsed light (IPL) is capable of entirely replacing thermal annealing (curing and contact formation) within back end processing of silicon heterojunction solar cells. In order to demonstrate this, full-size silicon heterojunction (SHJ) cells with IPL-processed screen-printed metal contacts are evaluated. Such cells reach conversion efficiencies of up to 23.0%. On average, IPL-annealed SHJ cells outperform their thermally treated pendants by 0.3-0.4% abs , in particular because of higher open-circuit voltages and fill factors. Moreover, IPL offers high throughput and low footprint. This results in a cost of ownership reduction potential of 6% rel compared to state-of-the-art thermal annealing.