Highly Transparent Paper For Electronic Devices

We are surrounded in a world of electronic devices that are an indispensable part of dailylife, such as portable computers, smart phones, television, ipad, solar cells, displays, andcameras. The increasing demand of electronics poses a growing environmental problem dueto the wide use of plastics as the substrates. This has led to a green initiative in pursuit ofrecyclable or environmentally friendly alternatives to plastic substrates to host electronics andincreased attention has been directed toward “green” electronics that are fabricated fromnatural materials using economically efficient production routes. Integrating specifictransparent paper into electronic devices with special requirements has become a hot researcharea recently that has attracted widespread interest in the scientific community because of itspotential capacity to enable the scalable and sustainable production of “green” electronicdevices.We demonstrate the first novel bilayer structural wood fiber/NFC hybrid paper that fufilsthe requirements of a high optical transmittance and superior smoothness for flexibleelectronics. In addition, it is less expensive than nanopaper due to the use of unbeaten woodfibers and writable. The first transparent paper touchscreen with excellent anti-glare effect inbright environments is demonstrated using the bilayer transparent and conductive paper as theflexible electrode.A novel transparent paper made of wood fibers that displays both ultrahigh opticaltransparency (~96%) and ultrahigh haze (~60%) was first reported, thus delivering an optimalsubstrate design for solar cell devices. Compared to previously demonstrated nanopapercomposed of wood-based cellulose nanofibers, this novel transparent paper has better dualperformance in transmittance and haze but also is fabricated at a much lower cost. In addition,we also demonstrate this with silicon slab by simply laminating a piece of such transparentpaper and observed its light reflectivity decreased by10~18%in the visible range.We report a novel, rationally designed, solution based silver nanowire (Ag NW)transparent paper that demonstrates a flexible, low cost, and scalable device ready transparentconducting electrode (TCE) with exceptional and stable optoelectronic properties. Its hightransmittance (91%) and low sheet resistance (13Ω/□) represent the highest reported figure ofmerit value for solution based TCEs according to conventional models. We also thoroughlyinvestigate the diffuse light scattering properties of our Ag NW paper with various techniquesthat elucidate the total optical haze as well as the diffuse scattering angle distribution for thisTCE. Through a simulation of the impact the optical properties of TCEs have on the light absorption in the conversion layers for various thinfilm solar cells, we demonstrate that ourAg NW paper induces greater light absorption than ITO for each simulated thinfilm solar cell.We aslo present the use of highly transparent paper with high optical haze forphotovailtic devices. By simply attaching this transparent paper to the surface of organic solarcell and GaAs cell, respectively, they separately indicate an enhanced power conversionefficiency of10%and23.91%for all angles of incident illumination. In addition, due to acombination of index contrast, surface texturing, and optical haze, this transparent paper leadsto a significant increase in light absorption for all wavelengths, which is nearly independentof the incident angle.We propose a facile method to manage the optical properties of paper through a rationaldesign. TEMPO(2,2,6,6-tetramethylpiperidine-1-oxyl radical)-oxidized micro-sized woodfibers with an average diameter of~27μm and average length of0.92mm were used toenhance the haze of paper, while NFC with a diameter of~30nm was used to decrease thehaze of paper. By adjusting the weight ratio of TEMPO-oxidized wood fibers to NFC,transparent paper fabricated by vacuum filtration possesses a tunable haze from18%to60%while retaining a transmittance over90%. In addition, the scattering angular distributionmeasurement was further conducted to elucidate the light scattering effect of varioustransparent papers with different haze.By simply depositing a layer of TEMPO-oxidized wood fibers (TOWFs), we are able totailor the optical properties of flexible glass dramatically from exhibiting low haze (<1%) tohigh haze (~56%) without compromising the total forward transmittance (~90%). Theinfluence of the TOWFs morphology on the optical properties of TOWFs-coated flexibleglass is also investigated. As the average fiber length decreases, the transmission haze ofTOWF-coated flexible glass also illustrates a decreasing trend.This inexpensive, renewable, sustainable, and scalable transparent paper with excellentperformance is a potentially revolutionary material for next generation “green” flexibleelectronics.