| Article ID | Journal | Published Year | Pages | File Type |
|---|---|---|---|---|
| 1549880 | Solar Energy | 2014 | 10 Pages |
•New phenomenon discovered and explained: Spontaneous hot spot formation in photovoltaics.•Numerical modeling captures time, spatial, and temperature scales of hot spot formation.•Sufficient substrate thermal conductivity can suppress hot spot formation.•Simple analytic equations characterize some aspects of the hot spot.
We present data exhibiting the spontaneous emergence of hot spots in forward biased thin film photovoltaics based on a-Si:H technology. These spots evolve over time, shrinking in their diameter and increasing in temperature up to approximately 300 °C above that of the surrounding area. Our numerical approach explores a system of many identical diodes in parallel connected through the resistive electrode and through thermal connectors, a model which couples electric and thermal processes. The modeling results show that hot spots emerge from a rather large area of nonuniform temperature, then collapse to local entities. Finally, we present a simplified analytical treatment establishing relations between the hot spot parameters. The technological importance of our findings is that they open a venue to improving the large area device performance and reliability by properly scaling the device thickness, substrate material, and thermal insulation.
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