Long-term reliability of silicon wafer-based traditional backsheet modules and double glass modules

An extensive program of series extended sequential long-term reliability stress including thermal cycling (TC) 600, damp heat (DH) 3000, 600 hours potential induced degradation (PID) and humidity freeze (HF) 50 were performed on silicon wafer-based traditional backsheet modules and double glass photovoltaic (PV) modules. The relative module maximum power (P_max) degradations of traditional backsheet modules are 3.87%, 7.34%, 13.3%, 33.73% and those of double glass modules are 2.78%, 3.12%, 2.27%, 2.72%, respectively. From all the above results, HF50 has a greater impact on P_max degradation of traditional backsheet modules, and a strong correlation is thereby found between the Water Vapor Transmission Rate (WVTR) of the backsheet and the P_max degradation. Traditional backsheet modules have higher WVTR and greater P_max degradation, while double glass modules are impermeable and have much lower P_max degradation. The key factor for excellent performance of Si wafer-based double glass PV modules is replacing the polymer backsheet by a glass panel with impermeability to water vapor, which enables double glass modules to offer much higher reliability and longer durability.