Our transparent cellulose nanofibrils composites (TCNC) directly from rotary-cutting poplar veneer (RPV) whose lignin can be easily stripped by our treatment. This TCNC is prepared by stripping lignin of original RPV and infiltrating epoxy resin (ER) into delignified RPV. This TCNC with two-layer delignified RPVs whose grains perpendicular (0/90°) to each other, which were solidified on solar cell while infiltrating ER. This TCNC with high transmittance (~90%), high haze (~90%), and equal refractive index fluctuation. Comparing with epoxy resin (ER), this TCNC can enhance open circuit voltage (VOC) from 1.16 to ~1.36 and short circuit density (JSC) from 30 to ~34 for the solar cell, and can enhance test fore from 0.155 kN to ~0.185 kN and displacement from 43.6 mm to ~52.5 mm. Wood is a kind of abundant organic macromolecule resource on the earth. Wood has excellent material properties which including high strength, high toughness, high modulus, low density, low thermal conductivity, biodegradability, sustainability and so on 1-3. The contents of wood mainly include cellulose and hemicellulose (≈70%), lignin (≈30%), and its cellulose and hemicellulose are colourless substance 4,5. New wood functionalization approaches have made it possible to combine load-bearing and functional properties in biobased wood structures 6-12. After stripping lignin or chromogenic groups, a kind of transparent wood composites (TWC) can be prepared by infiltrating the cavity of wood with a polymer 3,4,13-16. The TWC with high transmittance and high haze for light acquisition of solar cell, which have a significant enhancement in solar energy conversion efficiency 17-22. Some researchers have prepared TWC for light management in solar cells 17,18 , and they focused on TWC from radial-cutting veneer for two reasons. First, radial-cutting veneer is easier than rotary-cutting veneer in delignification. Second, radial-cutting veneer has equal refractive index fluctuation, but rotary-cutting veneer hasn't. However, rotary-cutting veneer could obtain far larger breadth from wood trunk to compare with radial-cutting veneer. Farmed poplar is a kind of widely distributed agro-forestry tree species in many nations due to its fast growth rate, short rotation period, multiple uses and high economical value 23-27. Reasonable use of farmed poplar can meet the human demand for TWC, and can avoid the consumption of natural forest resources 27. Poplar has the characteristics of ultra-short fibers, and its rotary-cutting poplar veneer (RPV) is better than radial-cutting poplar veneer (RPV) in mechanical properties 28,29. In our works, the kind of transparent cellulose nanofibrils composites (TCNC) directly from rotary-cutting poplar veneer (RPV) whose lignin can be easily stripped by our treatment. The RPV is from mature trunk of farmed poplar. This TCNC is prepared by stripping lignin of original RPV and infiltrating epoxy resin (ER) into delignified RPV. This TCNC with two-layer delignified RPVs whose grains perpendicular (0/90°) to each other, which w...
