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Location and Properties of Carrier Traps in mc‐Si Solar Cells Subjected to Degradation at Elevated Temperatures
Author(s) -
Mchedlidze Teimuraz,
Weber Joerg
Publication year - 2019
Publication title -
physica status solidi (a)
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.532
H-Index - 104
eISSN - 1862-6319
pISSN - 1862-6300
DOI - 10.1002/pssa.201900142
Subject(s) - materials science , solar cell , deep level transient spectroscopy , annealing (glass) , degradation (telecommunications) , carrier lifetime , analytical chemistry (journal) , electroluminescence , band gap , optoelectronics , silicon , passivation , chemistry , nanotechnology , composite material , layer (electronics) , electrical engineering , engineering , chromatography
Multi‐crystalline Si (mc‐Si) solar cells subjected to carrier‐induced efficiency degradation at elevated temperatures are studied using deep‐level transient spectroscopy (DLTS), capacitance‐voltage, and electroluminescence (EL) measurements. Commercially available passivated emitter and rear cell (PERC) mc‐Si solar cells are investigated after short annealing in the dark (at T = 200 °C for 20 min), after degradation by a constant forward current at 70 °C, and after regeneration annealing at 200 °C for 20 min. The degradation is detected in situ by EL imaging of the surface of the cell. Several n + p mesa‐diodes, selectively fabricated on the front surface of the solar cell, allow the characterization of locations with various levels of degradation and density of extended defects. The degree of the degradation correlates with the local active boron concentration. At all stages, traps associated with extended defects (i.e., dislocations, grain boundaries, precipitates, etc.) are detected by DLTS, and these traps are not affected by changes in the degree of degradation. Two minority‐carrier traps with energy level positions in the bandgap at Ec −0.19 eV and Ec −0.34 eV are detected only in the degraded solar cells in concentrations that correlate with the local degree of cell degradation.