Contact fault characterisation of complex silicon solar cells: a guideline based on current voltage characteristics and luminescence imaging

Abstract

Highest efficiency solar cells in industrial and R&D environments are increasingly sensitive to local performance limiting processing faults, which are best characterised by spatially resolved characterisation techniques. This work contains a discussion on the processing faults related to contact resistance and finger interruptions in interdigitated back contact silicon solar cells, which are prime example for a complex cell structure. Using experimental and simulated current-voltage measurements and luminescence images, we explore the strongly non-linear effect of poor local contact resistances on the global series resistance, fill factor, short circuit current density and efficiency. A good agreement between global and spatially resolved characterisation of faults is found, and potential artefacts are discussed. In conclusion, we present seven cases of contacting faults in interdigitated back contact cells with distinct characteristics that can be identified using a flow chart of experiments. The resulting guideline should assist silicon solar cell manufacturers in localising and quantifying local contacting faults that reduce the cells efficiency in manufacturing of complex solar cells.

Detection of finger interruptions in silicon solar cells using photoluminescence imaging

“…In this stage, the local R S defects of the interrupted fingers cannot be detected. The PL image at short circuit can only detect defects with extremely high R S,i [14] that are large enough to impede the extraction of carries and change the local short circuit current extraction, like a completely missed finger or four consecutively interrupted fingers. In the second stage, with the further increase of V appl , ∆PL increases to a peak value (∆PL max ) of 0.33 at an applied voltage of 0.476 V for ROI1.…”

Back‐Contacted Back‐Junction Si Solar Cells with Locally Overcompensated Diffusion Regions – Comparison of Buried Emitter and Floating Base Design

“…Interestingly, the “floating base” solar cell has a much lower local EQE compared to the “reference” and the “buried emitter” solar cell, and a clear distinction between electron‐ and hole‐collecting regions is less pronounced. In the case of the local τ eff , it can be seen that the highest values have been obtained in the hole‐collecting B‐diffusion region while the lowest values have been achieved in the electron‐collecting P‐diffusion region . For the “buried emitter” solar cell, τ eff is much higher than for the “reference” solar cell τ eff , especially in the hole‐collecting B‐diffusion regions.…”