Cu(In,Ga)Se2 mini-modules demonstrate damp heat stability exceeding 3000 h via advanced encapsulation and bias management

Cu(In,Ga)Se 2 (CIGSe) solar cells have rapidly advanced over the past decade; however, achieving robust long-term stability is a crucial issue that needs to be solved for their commercial success. Due to the heavy weight and rigid limitation of traditional glass cover, the long-term reliability of photovoltaic modules employing non-glass cover materials is still being developed and investigated. This study comprehensively evaluates a high-barrier flexible encapsulation scheme under extended damp heat (DH) testing. Two CIGSe mini-modules underwent a 3600-hour test, with one was continuously biased near its voltage at the maximum power point (Vmpp) and the other was left under unbiased conditions. Remarkably, both mini-modules exceed the IEC 61215-2 standards, maintaining over 97 % of their efficiencies after over 3000 h of the DH test. Furthermore, the impact of the continuous electrical operation during the DH test is also investigated. The mini-module under Vmpp bias sustained high performance during prolonged DH exposure, but interruption of the bias voltage led to an efficiency decline, which can be reversible. This observation suggests the potential for bias-driven stabilization mechanisms at the material or interface level, necessitating further in-depth investigation to optimize operational protocols for enhanced long-term reliability of flexible CIGSe solar cells in DH environments. The effectiveness of the demonstrated encapsulation strategy provides a significant step toward realizing the full potential of flexible CIGSe technology.