Highly Durable and Flexible Transparent Electrode for Flexible Optoelectronic Applications

Abstract

A highly-durable, highly-flexible transparent electrode (FTE) is developed by applying a composite made of a thin metal grid and a doped conducting polymer onto a colorless polyimide-coated NOA63 substrate. The proposed FTE exhibits a transparency of 90.7% at 550 nm including the substrate and a sheet resistance of 30.3 Ω/sq and can withstand both moderately high-temperature annealing (∼180 °C) and acidic solution (70 °C, pH 0.3) processes without performance degradation. The fabricated FTE yielded good mechanical stability under 10 000 cycles of bending deformations at a bending radius less than 1 mm without degradation of electrical conductivity. The high durability of the proposed FTE allows for the fabrication of flexible energy harvesting devices requiring harsh conditions, such as highly flexible perovskite solar cells (FPSCs) with a steady-state power conversion efficiency (PCE) of 12.7%. Notably, 93% of the original PCE is maintained after 2000 bending cycles at an extremely small bending radius of 1.5 mm. The FPSCs installed on curved surfaces of commercial devices drive them under various environments. The applicability of the proposed FTE is further confirmed via the fabrication of a flexible perovskite light-emitting diode. The proposed FTE demonstrates great potential for applications in the field of flexible optoelectronic devices.

Patterned few nanometer-thick silver films with high optical transparency and high electrical conductivity

“…[18][19][20] In contrast, metallic patterned grids and ultrathin lms do not have those problems. 5,6,[15][16][17] Previously-reported metal grids had either regular patterns fabricated through electron-beam lithography or photolithography, e.g., rectangles, [21][22][23][24][25][26][27][28] modied rectangles, 29 hexagons, 26,30 etc., or irregular patterns with self-forming cracks/ masks, e.g., titanium oxide, 31 egg white, 32,33 CA200, 32 leaf venation, 34,35 spider's silk web, 35 electro-spun bers, 36 all paint containing colloidal silicon dioxide, 37 cosmetic containing acrylic emulsion, 37 etc. In general, the grid lines are made narrow enough so that light can transmit through the sufficiently large spacing without loss and meanwhile thick enough to maintain a sufficiently high conductivity.…”

“…In general, the grid lines are made narrow enough so that light can transmit through the sufficiently large spacing without loss and meanwhile thick enough to maintain a sufficiently high conductivity. [21][22][23][24][25][26][27][30][31][32][33][34][35][36][37] Because of the opaque grid lines, the optical transparency is usually limited by the opening ratio (OR), which is dened as the ratio of the space area to the unit cell area. Sheet resistances, R sh , less than 1 U sq À1 have been reported with metallic grids that have micrometer thick grid lines.…”

“…It is comparable to and even higher than those of most thick metal grid based TCEs reported. 21,[23][24][25][26][27][28][29][30][31] Throughout the whole paper, the FoMs are calculated using the following widely-accepted expression: 53,54 FoM ¼ T 550…”

Flexible Electronics: Status, Challenges and Opportunities

“…The evaporation and sputtering of metals through shadow masks and photolithographic methods onto flexible substrates has been demonstrated numerously (Smith et al, 1997;Someya et al, 2004;Jain et al, 2005;Kang et al, 2008;Kaltenbrunner et al, 2013;Okita et al, 2013;Park et al, 2018). Metal oxides like indium tin oxide and fluorine-doped tin oxide are vastly utilized for optoelectronic applications due to their transparency and conductivity, however they offer limited flexibility due to their brittle nature (Jin et al, 2018). Thin layers of nanomaterials like graphene, carbon nanotubes, silver nanowires, and Ti 3 C 2 (MXene), as well as conductive polymers like PEDOT:PSS have been fabricated through solution processing techniques and have demonstrated favorable Young's modulus while maintaining high degrees of transparency, thus becoming a viable alternative for printed optoelectronic devices (Gao, 2017;Kim et al, 2017;Kim and Alshareef, 2020;Zhang et al, 2020).…”

Smart Sensing Systems Using Wearable Optoelectronics

“…To overcome these shortcomings, various research groups reduce the density of PEDOT by doping with the addition of enhancers, while increasing conductivity by maintaining PEDOT crosslinks. Jin et al engineered PEDOT:PSS by doping ethylene glycol . Doping the ethylene glycol inside PEDOT:PSS can reduce PSS density, which makes the PEDOT's rich domains.…”