Doped Layer Optimization for Silicon Heterojunctions by Injection-Level-Dependent Open-Circuit Voltage Measurements

Besides passivation of the c-Si absorber, provided mainly by the undoped buffer layer, the net doping of the silicon thin films plays a major role in the performance of silicon-based heterojunction (SHJ) solar cells. However, junction engineering is complex as high net doping often interferes with t...

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Bibliographic Details
Published in:IEEE journal of photovoltaics 2014-03, Vol.4 (2), p.566-574
Main Authors: Bivour, M., Reusch, M., Schroer, S., Feldmann, F., Temmler, J., Steinkemper, H., Hermle, M.
Format: Article
Language:English
Subjects:
Amorphous silicon
Buffer layers
Doping
heterojunction
Indium tin oxide
Lighting
Optimization
Passivation
Photovoltaic cells
Schottky barrier
Silicon wafers
Solar energy
Sun
TCO
Thin films
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Summary:Besides passivation of the c-Si absorber, provided mainly by the undoped buffer layer, the net doping of the silicon thin films plays a major role in the performance of silicon-based heterojunction (SHJ) solar cells. However, junction engineering is complex as high net doping often interferes with the interface passivation and the optical properties of the silicon thin films. We show that injection-level-dependent open-circuit voltage (Suns- Voc) measurements are a simple and valuable method for the characterization and optimization of the doped amorphous silicon (a-Si:H) layers. It is shown by experiment and device simulations that at high illumination intensities the Suns- Voc characteristic exhibits a strong signature of defect recombination within the a-Si:H, which is determined by the a-Si:H doping and the interfacial transparent conducting oxide (TCO) properties. This fact is exploited for a qualitative interpretation of the interplay between a-Si:H and the interfacial TCO properties. As a clear correlation between the Suns- Voc characteristic and the maximum power point conditions of the devices exists, fill factor (FF) losses attributed to the doped a-Si:H and the interfacial TCO properties can 1) be easily predicted in the early stage of device optimization on simple test structures, or 2) these FF losses can be identified and distinguished from other FF losses in the final device.
ISSN:2156-3381
2156-3403
DOI:10.1109/JPHOTOV.2013.2294757