In-Line Post-Process Scribing for Reducing Cell to Module Efficiency Gap in Monolithic Thin-Film Photovoltaics

Abstract

The gap between cell and module efficiency is a major challenge for all photovoltaic (PV) technologies. For monolithic thin film PV modules, a significant fraction of this gap has been attributed to parasitic shunts, and other defects, distributed across the module. In this paper, we show that it is possible to contain or isolate these shunt defects, using the state of the art laser scribing processes, after the fabrication of the series connected module is finished. We discuss three possible alternatives, and quantify the performance gains for each technique. We demonstrate that using these techniques, it is possible to recover up to 50% of the power lost to parasitic shunts, which results in 1-2% (absolute) increase in module efficiencies for typical thin film PV technologies.

An Illumination- and Temperature-Dependent Analytical Model for Copper Indium Gallium Diselenide (CIGS) Solar Cells

“…coupled module simulation framework to further investigate and reduce the cell-to-module efficiency gap [3], improve module reliability [6], as well as interpret thermal imaging measurements of solar modules [55].…”

“…The performance gain has not been fully reflected at the module level (current highest module efficiency ~17% [2]). Therefore, there are opportunities for manufacturing and design improvements to reduce the cell-to-module efficiency gap [3]- [5].…”

An Analysis of the Cost and Performance of Photovoltaic Systems as a Function of Module Area

“…It has been reported that one of the main causes of non-uniformity of thin-film solar modules (e.g., CIGS and CdTe) is the lognormal distributed shunt [17], which contributes significantly to the cell-to-module efficiency gap [18]. The lognormal distribution of shunt can be inherent in thin-film technologies, which originated from the fact that grain size in poly-crystalline films is lognormal distributed regardless of the choice of materials.…”

“…Changes in module design to reduce stress (e.g., the use of thicker glass) may be able to address some of these challenges if they were indeed observed in practice. Prior work suggests that although shunts or partial shading result in unsatisfactory degradation of module efficiency, novel geometry design and post-process scribing could be employed to enhance shadow tolerance for better reliability and isolate defects to improve overall module performance [18]. A complete understanding of the reliability of glass-glass modules in general is also still being developed.…”

“…We calculate the number of required diodes as follows, using a standard methodology outline in [18]: o Ran sensitivity analysis to this assumption in this report…”