EU PVSEC Programme Online
EU PVSEC 2021, 6 - 10 September 2021
Presentation: 2BO.14.5 Impact of Handling Defects towards SHJ Cell Parameters
Type: Oral
Date: Tuesday, 7th September 2021
15:15 - 16:45
Author(s): A. Fischer, I. Voicu, S. Pingel, A. Moldovan, J. Rentsch
Presenter / Speaker: A. Fischer, Fraunhofer ISE, Freiburg, Germany
Event: Conference Conference
Session: 2BO.14 Wafer-Based Silicon Heterojunction Solar Cells
Topic: 2. 3 Low Temperature Route for Si Cells
Summary / Abstract: The major challenge of wafer handling in photovoltaic mass production is the gentle transport at very high speed [1]. To stay competitive in terms of throughput at least one substrate per second must be picked up, transported and placed well oriented and positioned while reaching yield losses lower than 1 % [2]. For highly surface sensitive cell concepts like Silicon Heterojunctions the requirements increase concerning the purity and nature of the silicon surface, which becomes later the interface between the silicon base substrate and the passivation layer. As a starting point, a clean, defect-free and specifically Hterminated silicon surface is necessary before passivation [3]. To maintain these interface requirements, a new challenge in handling photovoltaic substrates is added: the handling system mostly consisting of vacuum- or Bernoulligrippers and conveyor belts must not affect the sensitive cleaned heated or non heated wafer surface. Aim and Approach Within this paper, a systematic approach will be presented to specify the influence of defects caused by vacuum grippers onto SHJ cell parameters. The grasping takes place at different processing stages. (1) The wafer is handled after wet-chemical cleaning and before a-Si layer deposition at the front side or rear side by plasma enhanced chemical vapor deposition (PECVD). (2) The wafer is handled after a-Si layer deposition at the front side or rear side by PECVD and before the deposition of a transparent conductive oxide (TCO) by physical vapor deposition (PVD). The study focuses on, the comparison between handling-induced defects originating from handling on the emitter or non-emitter side, and the comparison of handling-induced defects originating from handling before and after PECVD deposition. The analysis is carried out by means of I-V measurements on manufactured SHJ cells and by means of Suns Photoluminescence Imaging (SunsPLI) measurements on solar cell precursors. With the imaging method SunsPLI [4], pseudo fill factor (pFF) images and pseudo-efficiency (Pseudo) images are calculated using the assumption of a short-circuit current density (JSC) and measured implied open circuit Voltage (iVoc) images at different light intensities in the range between 0.005 Suns and 1.5 Suns. The handling-induced defects that occur are evaluated locally with the iVoc at 1 Sun, the calculated pFF- and Pseudo-images. With I-V-Measurements and SunsPLI Method it is possible to determine the global losses in Voc, FF, Jsc and efficiency for gripper induced defects, as well as the local losses in iVoc, pFF and pseudo-efficiency, which will be presented at the conference.