Hot spot runaway in thin film photovoltaics and related structures

TL;DR

This paper reveals that thin film diode structures like photovoltaics can spontaneously develop localized thermal runaway, causing nonuniformities that impact performance and reliability, and suggests design strategies to mitigate this.

Contribution

It introduces a linear stability analysis for thermal runaway in thin film diode systems, supported by numerical modeling, highlighting a previously unrecognized instability.

Findings

Localized thermal runaway can spontaneously occur in uniform thin film diodes.

The instability leads to nonuniform thermal and electrical behavior.

Proper device design can mitigate the thermal runaway effects.

Abstract

We show that thin film diode structures, such as photovoltaics and light emitting arrays, can undergo zero threshold localized thermal runaway leading to thermal and electrical nonuniformities spontaneously emerging in originally uniform systems. The linear stability analysis is developed for a system of thermally and electrically coupled two discrete diodes, and for a distributed system. These results are verified with numerical modeling that is not limited to small fluctuations. The discovered instability negatively affects the device performance and reliability. It follows that these problems can be mitigated by properly designing the device geometry and thermal insulation.