Solution aging and degradation of a transparent conducting polymer dispersion

Abstract

a b s t r a c tAs organic electronics improve, there is increased research interest on the longevity and stability of both the device and individual material components. Most of these studies focus on post deposition degradation and aging of the film. In this article, we examine the stability of polyelectrolyte dispersions before film coating. We observe substantial differences in the solution properties of the transparent conducting polymer, S-P3MEET, when comparing fresh versus aged dispersions and relate these solution differences to film properties. The aged dispersion contains large agglomerates and exhibits a typical shear-thinning rheological behavior, which results in non-uniformity of the spin-coated films. Near edge X-ray absorption fine structure measurements were used to differentiate the changes in bonding and oxidation states and show that aged S-P3MEET is more highly self-doped than fresh S-P3MEET. We also show that addition of acid, salt or heat to fresh S-P3MEET can accelerate the degradation/aging process but are subjected to different mechanisms. Conductivity measurements of S-P3MEET films illustrate that there is a tradeoff between increased work function and decreased conductivity upon perfluorinated ionomer (PFI) loading. The formation of nanostructure in solution is also correlated to film morphology variations obtained from atomic force microscopy. We expect that dispersion aging is a process that commonly exists in most solution-dispersed polyelectrolyte materials and that the methodologies presented in this paper might be beneficial to future degradation/stability studies.

Improved efficiency of inverted planar perovskite solar cells with an ultrahigh work function doped polymer as an alternative hole transport layer

“…29 A scanning tunneling microscopy study showed that PEDOT:PSS films have a phase-separated structure, resulting in anisotropic conductivity. 30,31 PEDOT:PSS films also have anisotropic optical properties due to their ordinary and extraordinary complex refractive index. 32 Furthermore, reports show that inverted PSCs based on PEDOT:PSS provide low V OC and short circuit current density (J SC ) due to the mismatched work function between PEDOT:PSS and the perovskite energy level.…”

“…The chemical structure of poly(thiophene-3-[2-(2-methoxyethoxy)ethoxy]-2,5-diyl) (S-P3MEET) mimics that of PEDOT: PSS; 30,31 however, the S-P3MEET polymer has never been taken into consideration as an HTL for inverted PSC devices. Herein, S-P3MEET was investigated as a new HTL for inverted planar triple-cation perovskite solar cells due to its self-doping ability, in which the polymer and its sulfonate moieties do not have phase separation like PEDOT:PSS HTLs do.…”

“…Herein, S-P3MEET was investigated as a new HTL for inverted planar triple-cation perovskite solar cells due to its self-doping ability, in which the polymer and its sulfonate moieties do not have phase separation like PEDOT:PSS HTLs do. 31,41 While S-P3MEET and PEDOT:PSS are both derivatives of polythiophene, S-P3MEET is self-doped by the sulfonate moieties that are linked to the thiophene rings, while PEDOT:PSS has the dopant poly(styrene sulfonate) (PSS) in solution. 30,31 To improve the alignment energy at the perovskite-S-P3MEET interface, we tuned the WF of S-P3MEET by adding a desirable weight ratio of PFI to the S-P3MEET solution.…”

“…31,41 While S-P3MEET and PEDOT:PSS are both derivatives of polythiophene, S-P3MEET is self-doped by the sulfonate moieties that are linked to the thiophene rings, while PEDOT:PSS has the dopant poly(styrene sulfonate) (PSS) in solution. 30,31 To improve the alignment energy at the perovskite-S-P3MEET interface, we tuned the WF of S-P3MEET by adding a desirable weight ratio of PFI to the S-P3MEET solution. The optoelectronic and chemical properties of the pristine and doped S-P3MEET films were characterized to determine the best inverted planar triple-cation PSC device.…”

Improved Anisotropic Thermoelectric Behavior of Poly(3,4-ethylenedioxythiophene):Poly(styrenesulfonate) via Magnetophoresis

“…In PEDOT:PSS, electrical charges hop between the PEDOT-rich phases across the insulating PSS phase 8 so that high variability in the processed morphology and physical properties of PEDOT:PSS leads to high variability in the electrical behavior. 9,10 Solvent additives and film post-treatment with secondary dopants have been shown to improve the electrical conductivity of PEDOT:PSS by aligning PEDOT centers. 1,11−13 However, this approach also decreases the effective Seebeck coefficient of the resulting CP.…”