RESEARCH ARTICLE Inﬂuence of cracks on the local current–voltage parameters of silicon solar cells Tobias M. Pletzer 1 * , Justus I. van Mölken 1 , Sven Rißland 2 , Otwin Breitenstein 2 and Joachim Knoch 1 1 RWTH Aachen University, Institute of Semiconductor Electronics, Sommerfeldstraße 24, D-52074 Aachen, Germany 2 Max Planck Institute of Microstructure Physics, Department 2, Weinberg 2, D-06120 Halle, Germany ABSTRACT The existence of cracks in silicon solar cells can drastically reduce the electrical performance of an individual cell and even of an entire photovoltaic module. An in-depth understanding of the inﬂuence of cracks on solar cells enables therefore calculations of the crack impact and other following effects on module level. This paper shows a detailed analysis of the electrical inﬂuence of cracks with two different spatially resolved methods including global and local current–voltage characteristics. The main inﬂuence of cracks is an increased recombination current density in the depletion region, which is clearly shown by spatially resolved dark lock-in thermography measurements with local current–voltage investigation. This increased recombination current density affects further cell parameters such as the efﬁciency, which is conﬁrmed also by the global current–voltage characteristics. The additionally used ratio image technique based on electroluminescence measurements is in comparison with the local current–voltage method, the more reliable and faster method for the crack detection itself, and allows on cell-level and module-level a continuous inspection of cracks. Copyright © 2013 John Wiley & Sons, Ltd. KEYWORDS cracks; electroluminescence; dark lock-in thermography; spatially resolved characterisation; silicon solar cells; local current– voltage parameters *Correspondence Tobias M. Pletzer, RWTH Aachen University, Institute of Semiconductor Electronics, Sommerfeldstraße 24, D-52074 Aachen, Germany. E-mail: pletzer@iht.rwth-aachen.de Received 8 July 2013; Revised 20 September 2013; Accepted 22 October 2013 1. INTRODUCTION Cracks or micro-cracks in silicon (Si) wafers or solar cells can reduce the electrical performance [1] or mechanical stability of cells, which could result in a destroyed cell or decreased output power of photovoltaic (PV) modules. Cracks occur during the solar cell processing due to the stress resulting from particular process steps with high temperatures as well as the mechanical handling of cells in manufacturing or during the transport of solar cells or PV modules. In the case of PV modules, a strong wind load or a heavy snow weight can induce sufﬁcient mechanical stress for crack formation [2]. Electroluminescence (EL) camera based imaging [3] is a well-established measurement technique to identify cracks in solar cells and to characterise cells as well as PV modules in a fast way with high resolution. Furthermore, the preparing of ratio images [1] with EL images before and after crack formation allows a detailed investigation of cracks. Cracks can also be identiﬁed with the dark lock-in thermography (DLIT) [4]. The DLIT technique does not provide high resolution but allows a quantitative analysis of cells. The quantitative analysis of solar cells with DLIT allows the determination of local current–voltage (I–V) data like open circuit voltage (V OC ), ﬁll factor (FF) and efﬁciency (η) in a spatially resolved manner [5,6]. Also, the two-diode model parameters, alias internal cell parameters such as saturation current density of the ﬁrst diode (J 01 ) linked to the recombination outside the space charge region (SCR), saturation current density of the second diode (J 02 ) linked to recombination within the SCR and parallel (or shunt) resistance (R P ), can be determined with this method. The series resistance (R S ) is obtained according to the so-called recombination current and series resistance imaging method PROGRESS IN PHOTOVOLTAICS: RESEARCH AND APPLICATIONS Prog. Photovolt: Res. Appl. (2013) Published online in Wiley Online Library (wileyonlinelibrary.com). DOI: 10.1002/pip.2443 Copyright © 2013 John Wiley & Sons, Ltd.