High-forward-bias transport mechanism in a-Si:H/c-Si heterojunction solar cells

✍ Scribed by Schulze, T. F. ;Korte, L. ;Conrad, E. ;Schmidt, M. ;Rech, B.

• Book ID: 105365714
• Publisher: John Wiley and Sons
• Year: 2010
• Tongue: English
• Weight: 461 KB
• Volume: 207
• Category: Article
• ISSN: 0031-8965
• DOI: 10.1002/pssa.200982747

✦ Synopsis

Abstract

In order to elucidate the transport mechanism in a‐Si:H/c‐Si heterojunction solar cells under high forward bias (U > 0.5 V), we conducted temperature‐dependent measurements of current–voltage (I–V) curves in the dark and under illumination. ZnO:Al/(p)a‐Si:H/(n)c‐Si/(n^+^)a‐Si:H cells are compared with inversely doped structures and the impact of thin undoped a‐Si:H buffer layers on charge carrier transport is explored. The solar cell I–V curves are analyzed employing a generalized two‐diode model which allows fitting I–V data for a broad range of samples. The fitting results are complemented with numerical simulations using AFORS‐HET under consideration of microscopic a‐Si:H parameters as determined by constant‐final‐state‐yield photoelectron spectroscopy (CFSYS) to identify possible origins for a systematic increase of the high‐forward‐bias ideality factor along with the open‐circuit voltage (V~oc~). It is further shown that also for a‐Si:H/c‐Si heterojunctions, dark I–V curve fit parameters can unequivocally be linked to V~oc~ under illumination, which may prove helpful for device assessment.