A round Robin-Highliting on the passivating contact technology

Abstract

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 mΩcm2 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.

Overview of key results achieved in H2020 HighLite project helping to raise the EU PV industries' competitiveness

“…In a first step, a large round‐robin experiment involving five of the leading EU PV institutes was organized by Fraunhofer ISE to evaluate various tunnel oxide passivated contacts (TOPCon) layers prepared by plasma enhanced chemical vapor deposition (PECVD) or by low pressure chemical vapor deposition (LPCVD) and using various dielectric capping layers. For all the approaches, dark saturation current‐densities ranging between 2 and 10 fA/cm 2 as shown in Figure 5A and contact resistivities below 10 mΩ.cm 2 have been achieved 34 . Additional characterization based on scanning spreading resistance microscopy (SSRM) revealed that many of those optimized layers feature local regions of doping enhancement favoring current transport 35 .…”

“…(A) Total dark saturation density J0 for TOPCon samples with (0.48 mm finger pitch) and without metallization (infinite finger pitch) for different set peak firing temperatures in the range of 815–855°C 34 . (B) Laser scanning microscope image of local p + poly‐Si finger surrounded by textured silicon surface produced by a novel laser crystallization step for maskless structuring of p + poly‐Si 24 …”

“…In a first step, a large round-robin experiment involving five of the leading EU PV institutes was organized by Fraunhofer ISE to evaluate various tunnel oxide passivated contacts (TOPCon) layers prepared by plasma enhanced chemical vapor deposition (PECVD) or by low pressure chemical vapor deposition (LPCVD) and using various dielectric capping layers. For all the approaches, dark saturation current-densities ranging between 2 and 10 fA/cm 2 as shown in Figure 5A and contact resistivities below 10 mΩ.cm 2 have F I G U R E 4 Externally confirmed efficiency of 24.1% for a full area M2-size (area = 244.5 cm 2 ) SHJ cell with a shingle metallization layout produced at CEA-INES pilot-line in 2021 F I G U R E 5 (A) Total dark saturation density J0 for TOPCon samples with (0.48 mm finger pitch) and without metallization (infinite finger pitch) for different set peak firing temperatures in the range of 815-855 C. 34 (B) Laser scanning microscope image of local p + poly-Si finger surrounded by textured silicon surface produced by a novel laser crystallization step for maskless structuring of p + poly-Si. 24 been achieved.…”

“…Latest batches using high-quality n-type wafers in G1 format are now giving average cell efficiencies above 23.0% with results mainly limited by recombination losses as also reported by other companies using ZEBRA technology. 23 Various approaches have been investigated by the HighLite pro- 34 (B) Laser scanning microscope image of local p + poly-Si finger surrounded by textured silicon surface produced by a novel laser crystallization step for maskless structuring of p + poly-Si. 24 [Colour figure can be viewed at wileyonlinelibrary.com] been achieved.…”

“…24 [Colour figure can be viewed at wileyonlinelibrary.com] been achieved. 34 Additional characterization based on scanning spreading resistance microscopy (SSRM) revealed that many of those optimized layers feature local regions of doping enhancement favoring current transport. 35 The fact that similar results can be realized by multiple institutes using different approaches and equipment is expected to drive costs down and contribute to the increased adoption of TOPCon technology in various cell concepts.…”