Photodiodes based on wood pulp fiber networks

Abstract

Wood cellulose is a desirable inexpensive, abundant and biodegradable substrate material for flexible organic electronics. While paper-based conductors are easily achieved, their applicability for diode architectures is challenging. To diminish short circuits, smoothing fillers and coatings are used before diode deposition. In this report, an alternative approach for use of cellulose in organic photovoltaics is demonstrated, using natural, rough unmodified kraft pulp fiber networks as a carrier of a diode architecture. Silver nanowires are adsorbed by the hydroxyl groups of cellulose fiber, forming the semi-transparent anode. The follow-on coatings for the diode are simply deposited as a mantle on these fiber anodes. The potential of this approach is demonstrated by the first production of cellulose fiber-based P3HT:PCBM photovoltaic devices, showing clear diode behaviour in the dark and a significant photoresponse under illumination. Fill factors near 35 % and open-circuit voltages of 0.2 V were achieved without any optimization. Devices show even noticeable photocurrent at low unfavourable light conditions, indicating their advantageous capture of stray light within the paper fiber network. These results highlight that for “paper” diodes, its natural properties can be turned into advantages, instead of seeking routes to suppress them.