A Generalized Theory Explains the Anomalous Suns-V-oc Response of Si Heterojunction Solar Cells

作者：Chavali Raghu Vamsi Krishna^*; Li Jian V; Battaglia Corsin; De Wolf Stefaan; Gray Jeffery Lynn; Alam Muhammad Ashraful

来源：IEEE Journal of Photovoltaics, 2017, 7(1): 169-176.

DOI：10.1109/JPHOTOV.2016.2621346

• Amorphous semiconductors
• current-voltage (J-V) characteristics
• heterojunctions (HJs)
• modeling and simulation
• silicon
• solar cells or photovoltaics
• Suns-V-oc

Suns-V-oc measurements exclude parasitic series resistance effects and are, therefore, frequently used to study the intrinsic potential of a given photovoltaic technology. However, when applied to a-Si/c-Si heterojunction (SHJ) solar cells, the Suns-V-oc curves often feature a peculiar turnaround at high illumination intensities. Generally, this turn-around is attributed to extrinsic Schottky contacts that should disappear with process improvement. In this paper, we demonstrate that this voltage turnaround may be an intrinsic feature of SHJ solar cells, arising from the heterojunction (HJ), as well as its associated carrier-transport barriers, inherent to SHJ devices. We use numerical simulations to explore the full current-voltage (J-V) characteristics under different illumination and ambient temperature conditions. Using these characteristics, we establish the voltage and illumination-intensity bias, as well as temperature conditions necessary to observe the voltage turnaround in these cells. We validate our turnaround hypothesis using an extensive set of experiments on a high-efficiency SHJ solar cell and a molybdenum oxide (MoOx) based hole collector HJ solar cell. Our work consolidates Suns-V-oc as a powerful characterization tool for extracting the cell parameters that limit efficiency in HJ devices.

• 出版日期2017-1