Encapsulation-free crystalline silicon photovoltaic modules and their hygrothermal and thermal-cycle tolerance

Abstract

A novel concept of unencapsulated modules was developed to avoid many degradation phenomena originating from encapsulants, reduce material costs, and also allow for both easy cell repair and easy recycling of modules. The reliability and durability of the novel concept modules were investigated using damp-heat (DH) testing, thermal-cycle (TC) testing, and sequential testing including DH and TC testing. No large reduction in maximum power after DH testing for 2700 h or TC testing for 1000 cycles was found for unencapsulated modules, irrespective of cell-connection method, cell spacing, or the existence of intentional microcracks. However, because of thermomechanical stress, unstable contact between interconnector ribbons and busbar electrodes was found after TC testing. Superiority of shingling connections was found for this novel concept of unencapsulated modules.