A New Strategy for Fabricating Flexible Organic Solar Cells by Spraying Perchloric Acid

Original Article:
Metal oxide-free flexible organic solar cells with 0.1 M perchloric acid sprayed polymeric anodes

Juanyong Wan, et al.

J. Mater. Chem. A, 2020, 8, 21007-21015

10.1039/D0TA07934K

Flexible organic solar cells (OSCs) have become an active research area due to their low cost, light weight, facile fabrication, wear resistance, and portability. Among them, poly(3,4-ethylenedioxythiophene): poly(styrenesulfonate) (PEDOT: PSS) is a promising transparent electrode due to its low cost, high transparency, good flexibility, and smoothness, etc. The optical and electrical properties of polymer electrodes are enhanced to the desired level through using strong acid soaking and dopant blending treatments, such as the traditional sulfuric acid (H₂SO₄) soaking method. However, due to the strong oxidizing and powerful dehydration properties, H₂SO_{4 destroys the underlying plastic substrates for flexible device integration.}

Herein, the researchers propose a new perchloric acid (HClO₄) spray-doping method for efficient flexible OSCs. The results suggest that this work paves the way for the realization of PEDOT: PSS anodes with high conductivity, suitable work function, and high flexibility for high-performance flexible OSCs and other optoelectronic devices.

The HClO₄ spray doping strategy shows advantages in the following aspects:

> HClO₄ is considered the strongest inorganic acid with ultrahigh acidity compared to H₂SO₄, thereby providing strong protonation of hydrogen ions (H+) to insulating PSS for increasing the conductivity of the film.

> Owing to the chlorine-oxygen polar bonds of HClO₄ with uncoupled charge centers, it is able to polarize PEDOT in the polymer matrix for high work function anodes.

> It may minimize the energy level mismatch between the anode, hole transport layer and electron donor of the active mixture to create a small potential battery at the interface.

> HClO₄ spray doping avoids direct contact between strong acid and plastic substrate, thus greatly improving device flexibility.

Chemicals Related in the Paper:

Catalog Number	Product Name	CAS Number
ACM155090838	Poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate)	155090-83-8