Research team at the University of Virginia extended an earlier laser-based recycling of glass-backsheet to bifacial dual-glass mini-modules measuring up to 421 × 320 mm
Front- and rear-side laser treatment separates the module into front glass, silicon cells and rear glass for further recovery
The study estimates a $5.33 recycling cost per commercial dual-glass module, while further silver extraction remains necessary
Researchers at the University of Virginia have adapted a laser-based separation method for dual-glass PV modules. The laboratory-scale study tested dual-glass mini-modules measuring up to 421 × 320 mm. The team, led by Dr. Mool C Gupta, had earlier developed the process for glass-backsheet modules and has now extended it to glass-glass designs (see Selective Laser Heating Applied To Detach Backsheet In PV Recycling).
For bifacial dual-glass modules, the front and rear sides are irradiated sequentially or simultaneously, with simultaneous treatment reducing processing time. The treatment separates the module into three layers: front glass with EVA, silicon cells, and rear glass with EVA. The glass-EVA layers are immersed in hot toluene at 80 °C for 10 to 20 minutes, followed by cleaning with isopropyl alcohol (IPA). The recovered glass showed average optical transmission above 90%. The cells were then cleaned ultrasonically in IPA at a concentration above 99%. Their metallization grid remained intact, with no visible macrocracks, leaving the cells available for downstream silver recovery.
The process directs a focused laser onto the silicon cells, where optical absorption generates heat. This thermally weakens or decomposes the adjacent encapsulant, allowing the glass to be mechanically detached.
The silicon surface temperature can reach 1,408 °C, well above EVA’s thermal decomposition range of 350 °C to 450 °C. At these temperatures, EVA undergoes deacetylation, releasing acetic acid and leaving a highly unsaturated polyene backbone. Further crosslinking under limited oxygen produces the carbon-rich residues observed on the separated surfaces.
For these experiments, a pulsed near-infrared laser was used; at 1064 nm wavelength, 100 ns pulse duration, and 80 kHz repetition rate, the maximum average power was 50 W. The parameters were tuned based on the module configuration and the interface of interest.
The earlier monofacial process differs at the rear side: a continuous-wave (CW) laser at 1,070 nm softens the rear-side EVA so that the backsheet can be removed. A subsequent pulsed near-infrared laser thermally decomposes the front-side EVA, separating the glass-EVA laminate from the silicon cells.
The study also covered a techno-economic analysis in which the cost of recycling a mainstream dual-glass module was estimated to be $5.33 and $8.06 for a glass-backsheet module. Additionally, the value of recovered materials using this process is estimated to be $9 to $13 per module. The study, titled High-Power Laser Recycling of Crystalline Silicon Photovoltaic Modules, is published in Solar Energy Materials and Solar Cells, Elsevier, and can be accessed here.
