Trap-Assisted Dopant Compensation Prevents Shunting in Poly-Si Passivating Interdigitated Back Contact Silicon Solar Cells

Journal Article · Wed Sep 01 00:00:00 EDT 2021 · ACS Applied Energy Materials

DOI:https://doi.org/10.1021/acsaem.1c01775· OSTI ID:1820578

Hartenstein, Matthew B. ^[1]; Stetson, Caleb ^[1]; Nemeth, William ^[2]; LaSalvia, Vincenzo ^[2]; Harvey, Steven P. ^[2]; Theingi, San ^[2]; Page, Matthew ^[2]; Jiang, Chun-Sheng ^[2]; Al-Jassim, Mowafak M. ^[2]; Young, David L. ^[2]; Agarwal, Sumit ^[1]; Stradins, Paul ^[1]

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1. Colorado School of Mines, Golden, CO (United States); National Renewable Energy Lab. (NREL), Golden, CO (United States)
2. National Renewable Energy Lab. (NREL), Golden, CO (United States)

Using a trap-assisted compensation model, we explain why polycrystalline Si (poly-Si) passivating contacts are able to achieve low leakage current between the doped fingers of interdigitated back contact (IBC) monocrystalline Si solar cells despite mixing of boron and phosphorus dopants in the isolation region. The fill factor of IBC solar cells is strongly affected by the electrical isolation region between n- and p-type fingers, as this region is critical in minimizing shunting losses. During fabrication of monocrystalline Si solar cells with poly-Si passivating contacts, the intrinsic poly-Si isolation region inevitably gets contaminated with both p- and n-type dopants. Using dopant profiles measured with time-of-flight secondary ion mass spectrometry and scanning probe measurements of the isolation region, we demonstrate that despite the dopant spreading during cell processing, a well-compensated region between the doped fingers exists that prevents shunting. The trap-assisted dopant compensation mechanism significantly widens the compensated region to tens of microns, where the residual dopant densities are below the trap density. This enables a high-resistivity region, resulting in low shunt current. Using one-dimensional (1-D) finite element diode simulations, we identify the design parameters and experimental conditions under which a sufficiently resistive region can form. Furthermore, our measurements of 2-D local resistivity and work function maps across the isolation region using scanning spreading resistance microscopy and Kelvin probe force microscopy demonstrate the existence of a highly resistive, wide compensated region and confirm our proposed compensation mechanism. For our structures, this region is ~25 µm in width within a ~150 µm wide finger isolation region with nearly 3 orders of magnitude higher resistivity than the regions dominated by a single type of dopant.

• Research Organization: Colorado School of Mines, Golden, CO (United States); National Renewable Energy Laboratory (NREL), Golden, CO (United States)
• Sponsoring Organization: USDOE Office of Energy Efficiency and Renewable Energy (EERE), Renewable Power Office. Solar Energy Technologies Office
• Grant/Contract Number: AC36-08GO28308; EE0007553
• OSTI ID: 1820578
• Alternate ID(s): OSTI ID: 1897214
• Report Number(s): NREL/JA-5900-80796; MainId:78574; UUID:fb7b62b2-efa2-4be0-beca-59cc90cd0b40; MainAdminID:61762
• Journal Information: ACS Applied Energy Materials, Journal Name: ACS Applied Energy Materials Journal Issue: 10 Vol. 4; ISSN 2574-0962
• Publisher: American Chemical Society (ACS)
• Country of Publication: United States
• Language: English

Related Subjects

14 SOLAR ENERGY
Si PV
Silicon photovoltaics
passivating contacts
interdigitated back contacts
device simulation
dopant compensation
device simulation
dopant compensation
interdigitated back contacts
passivating contacts
silicon photovoltaics