Improved Performance of OLEDs on Cellulose/Epoxy Substrate Using Adenine as a Hole Injection Layer

Organic light-emitting diodes (OLED) fabricated from all natural materials will lead to renewable, sustainable, and potentially inexpensive organic optoelectronics. Achieving this goal will require reimagining all the various aspects of the OLED with natural-based renewable materials. Here, we replace the common substrate, electrode, and hole injection layer in the OLED structure with cellulose, gold, and the DNA nucleobase adenine. Gold films are used as semitransparent electrodes on plant-based cellulose substrates, providing flexible anodes that are highly conductive without annealing. A lift-off fabrication method (template stripping) employed UV curable epoxy to transfer patterned gold from silicon to cellulose. The gold has excellent adhesion to the epoxy (is not damaged when wiped), and the two serve as a smoothing layer for the cellulose substrate, resulting in very uniform OLED emission. DNA and DNA nucleobases are demonstrating to be versatile materials in natural electronics due to their wide energy level range. We found that adenine as a hole injection layer on gold can overcome challenges of charge injection into the organic semiconductors, increasing OLED maximum luminance and emission efficiency 4-5x on both glass and cellulose substrates through increases in current (hole injection): on glass, from similar to 12500 to 45000 cd/m(2) and from 5 to similar to 32 cd/A; on cellulose, from similar to 2000 to 8400 cd/m(2) and from 3 to similar to 14 cd/A. These results expand the utility of the DNA bases for naturally based electronics and demonstrate practical methods to integrate cellulose as a biodegradable substrate.