Title: Tunnel oxide passivated contacts formed by ion implantation for applications in silicon solar cells

Abstract

Passivated contacts (poly-Si/SiO_x/c-Si) doped by shallow ion implantation are an appealing technology for high efficiency silicon solar cells, especially for interdigitated back contact (IBC) solar cells where a masked ion implantation facilitates their fabrication. This paper presents a study on tunnel oxide passivated contacts formed by low-energy ion implantation into amorphous silicon (a-Si) layers and examines the influence of the ion species (P, B, or BF2), the ion implantation dose (5 × 10¹⁴ cm^–2 to 1 × 10¹⁶ cm^–2), and the subsequent high-temperature anneal (800 °C or 900 °C) on the passivation quality and junction characteristics using double-sided contacted silicon solar cells. Excellent passivation quality is achieved for n-type passivated contacts by P implantations into either intrinsic (undoped) or in-situ B-doped a-Si layers with implied open-circuit voltages (iV_oc) of 725 and 720 mV, respectively. For p-type passivated contacts, BF2 implantations into intrinsic a-Si yield well passivated contacts and allow for iV_oc of 690 mV, whereas implanted B gives poor passivation with iV_oc of only 640 mV. While solar cells featuring in-situ B-doped selective hole contacts and selective electron contacts with P implanted into intrinsic a-Si layers achieved V_oc of 690 mV and fill factor (FF) of 79.1%, selective hole contactsmore » realized by BF₂ implantation into intrinsic a-Si suffer from drastically reduced FF which is caused by a non-Ohmic Schottky contact. Lastly, implanting P into in-situ B-doped a-Si layers for the purpose of overcompensation (counterdoping) allowed for solar cells with V_oc of 680 mV and FF of 80.4%, providing a simplified and promising fabrication process for IBC solar cells featuring passivated contacts.« less

Authors:

Reichel, Christian ^[1]; Feldmann, Frank ^[2]; Müller, Ralph ^[2]; Reedy, Robert C. ^[3]; Lee, Benjamin G. ^[3]; Young, David L.  ^[3];

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Stradins, Paul ^[3]; Hermle, Martin ^[2]; Glunz, Stefan W. ^[2]

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+ Show Author Affiliations

1. Fraunhofer Inst. for Solar Energy Systems (ISE), Freiburg (Germany); National Renewable Energy Lab. (NREL), Golden, CO (United States)
2. Fraunhofer Inst. for Solar Energy Systems (ISE), Freiburg (Germany)
3. National Renewable Energy Lab. (NREL), Golden, CO (United States)

Publication Date:

Mon Nov 23 00:00:00 EST 2015

Research Org.:

National Renewable Energy Lab. (NREL), Golden, CO (United States)

Sponsoring Org.:

USDOE SunShot Program to Advance Solar Cell Efficiency II (FPACE); German Federal Ministry for Economic Affairs and Energy

OSTI Identifier:

1235416

Alternate Identifier(s):

OSTI ID: 1226875

Report Number(s):

NREL/JA-5J00-65649
Journal ID: ISSN 0021-8979; JAPIAU

Grant/Contract Number:  

AC36-08GO28308; EE0006336

Resource Type:

Accepted Manuscript

Journal Name:

Journal of Applied Physics

Additional Journal Information:

Journal Volume: 118; Journal Issue: 20; Related Information: Journal of Applied Physics; Journal ID: ISSN 0021-8979

Publisher:

American Institute of Physics (AIP)

Country of Publication:

United States

Language:

English

Subject:

14 SOLAR ENERGY; 36 MATERIALS SCIENCE; amorphous semiconductors; passivation; ion implantation; silicon doping; silicon solar cells; semiconductor structures; oxides; Ohmic contacts; semiconductor materials; ion sources; chemical vapor deposition; electrical properties and parameters; solar cells; annealing