Potential-induced degradation for encapsulated n-type IBC solar cells with front floating emitter

Studying encapsulated n-type interdigitated back contact (IBC) solar cells with front floating emitter (FFE) we observe a power degradation mechanism which behaves similar to the PID-p degradation for n-type IBC solar cells with front surface field described in [1] or for bifacial n-type solar cells in [2]. This power drop is not shunt-related and arises as loss of short circuit current and open circuit voltage in analogy to the findings in [1]. The power degradation occurs when biasing FFE-IBC minimodules with negative potential against the ground and can be fully regenerated by reversing the polarity of the bias potential. The susceptibility to PID for our IBC minimodules depends on the encapsulation material to higher or lesser extent; until now no material was identified which can totally prevent PID. Bifacial IV measurements and EL recordings let us conclude that the PID we observe is non-local and causes a homogenous degradation of the front surface of the solar cell. Silvaco Atlas simulations show that a total loss of surface passivation is not sufficient to explain the effect. (C) 2015 Published by Elsevier Ltd.