Rapid preparation of highly transparent paper with high built-in haze by an ion exchange approach

Highly transparent paper with 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) radical-oxidized wood fibers (TOWFs) is a nascent sustainable photonic material for optoelectronics. However, its relatively low built-in haze and poor production efficiency are two remaining challenges. In this work, a facile and efficient ion exchange approach is proposed to address above obstacles by converting Na+ on their surface into Ca2+, thus enabling the rapid fabrication of highly transparent (90.0%) paper with high built-in haze (93.5%). Moreover, the relationship between Ca2+ concentration and the optical properties and production efficiency of transparent paper is explored. When the Ca2+ concentration increases from 0 to 0.8 mmol/g, the haze rises from 68.6% to 93.5% while maintaining a 90.0% transparency, and the filtration time decreases from 62.5 to 17.5 min. Finally, two application cases of this transparent paper for increasing the device performance of light-emitting diode (LED) and perovskite solar cell are demonstrated. This work proposes a facile and efficient method to simultaneously enhance the build-in haze and production efficiency of highly transparent paper with TOWFs and may bring us a step further towards preparing transparent and hazy paper on an industrial scale.