A green method to separate different layers in photovoltaic modules by using DMPU as a separation agent

Crystalline silicon photovoltaic (PV) modules have dominated the photovoltaic market for a long time and the recycling of crystalline silicon PV modules has become a critical issue due to their limited service life. The separation of glass and backsheet bonded by EVA film is critical to the separation of PV modules for the separation of different layers in PV modules is the premise of adequately recycling valuable elements such as Ag, Al, and Si. Traditional separation reagents, such as toluene, O-dichlorobenzene, and trichloroethylene, are all highly toxic which may cause harm to human body and pollute the environment. This paper innovatively proposes using green separation reagent DMPU (N,N′-dimethylpropenylurea, C6H12N2O) to separate different layers in PV modules. Constituents of each layer in the whole were analyzed by using SEM/EDS, XRD, XRF, and FTIR. Effects of different pieces, reaction temperatures, solid-liquid ratios, and ultrasonic powers were then investigated on the separation ratio, glass recovery ratio and backsheet peeling time. Meanwhile, separation comparison between DMPU and toluene on the separation ratio and silicon wafer breaking degree was also studied. Compared with toluene, the solar cell separated by DMPU can keep its initial size which is convenient for further resource recovery. Separation mechanism of different layers caused by DMPU was also studied by SEM, FTIR, and GC-MS. This study has significant implications for developing environmentally friendly and efficient separation reagents for recycling PV modules.