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Title: Crystalline Si Surface Passivation with Nafion for Bulk Defects Detection with Electron Paramagnetic Resonance

Journal Article · · ACS Applied Materials and Interfaces
ORCiD logo [1];  [2];  [3]; ORCiD logo [2]; ORCiD logo [2];  [2];  [2];  [2];  [2]; ORCiD logo [2]; ORCiD logo [1];  [2]
  1. Colorado School of Mines, Golden, CO (United States); National Renewable Energy Laboratory (NREL), Golden, CO (United States)
  2. National Renewable Energy Laboratory (NREL), Golden, CO (United States)
  3. Colorado School of Mines, Golden, CO (United States)
+ Show Author Affiliations

Here, in monocrystalline Si (c-Si) solar cells, identification and mitigation of bulk defects are crucial to achieving a high photoconversion efficiency. To spectroscopically detect defects in the c-Si bulk, it is desirable to passivate the surface defects. Passivation of the c-Si surface with dielectrics such as Al2O3 and SiNx requires deposition at elevated temperatures, which can influence defects in the bulk. Herein, we report on the passivation of different Czochralski (Cz) Si wafer surfaces by an organic copolymer, Nafion. We test the efficacy of the surface passivation at temperatures ranging from 6 to 473 K to detect bulk defects using electron paramagnetic resonance (EPR) spectroscopy. By comparing with state-of-the-art passivation layers, including Al2O3 and liquid HF/HCl, we found that at room temperature, Nafion can provide comparable passivation of n-type Cz Si with an implied open-circuit voltage (iVoc) of 713 mV and a recombination current prefactor Jo of 5 fA/cm2. For p-type Cz Si, we obtained an iVoc of 682 mV with a Jo of 22.4 fA/cm2. Scanning electron microscopy and photoluminescence reveal that Nafion can also be used to passivate the surface of c-Si solar cell fragments scribed from a solar cell module by using a laser. Consistent with previous studies, analysis of the EPR spectroscopy data confirms that the H-terminated surface is necessary, and fixed negative charge in Nafion is responsible for the field-effect passivation. While the surface passivation quality was maintained for almost 24 h, which is sufficient for spectroscopic measurements, the passivation degraded over longer durations, which can be attributed to surface SiOx growth. These results show that Nafion is a promising room-temperature surface passivation technique to study bulk defects in c-Si.

Research Organization:
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
OSTI ID:
2349501
Report Number(s):
NREL/JA--5K00-89862; MainId:90641; UUID:9b6c7883-2e69-4ea6-b20a-054c9fa2f707; MainAdminId:72586
Journal Information:
ACS Applied Materials and Interfaces, Journal Name: ACS Applied Materials and Interfaces Journal Issue: 17 Vol. 16; ISSN 1944-8244
Publisher:
American Chemical Society (ACS)Copyright Statement
Country of Publication:
United States
Language:
English

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14 SOLAR ENERGY
36 MATERIALS SCIENCE
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
Al2O3 dielectric passivation
crystalline silicon
electron paramagnetic resonance
nafion
photoluminescence
surface passivation