TY - JOUR
T1 - A generalized theory explains the anomalous suns- VOC response of si heterojunction solar cells
AU - Chavali, Raghu Vamsi Krishna
AU - Li, Jian V.
AU - Battaglia, Corsin
AU - De Wolf, Stefaan
AU - Gray, Jeffery Lynn
AU - Alam, Muhammad Ashraful
N1 - Publisher Copyright:
© 2011-2012 IEEE.
Copyright:
Copyright 2018 Elsevier B.V., All rights reserved.
PY - 2017/1
Y1 - 2017/1
N2 - Suns-VOC 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- Voc 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- $V{{\rm{oc}}}$ as a powerful characterization tool for extracting the cell parameters that limit efficiency in HJ devices.
AB - Suns-VOC 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- Voc 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- $V{{\rm{oc}}}$ as a powerful characterization tool for extracting the cell parameters that limit efficiency in HJ devices.
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U2 - 10.1109/JPHOTOV.2016.2621346
DO - 10.1109/JPHOTOV.2016.2621346
M3 - Article
AN - SCOPUS:84997795082
VL - 7
SP - 169
EP - 176
JO - IEEE Journal of Photovoltaics
JF - IEEE Journal of Photovoltaics
SN - 2156-3381
IS - 1
M1 - 7756368
ER -