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https://doi.org/10.1007/s11837-020-04361-8  2020 The Minerals, Metals & Materials Society

ADVANCED COATING AND THIN FILM MATERIALS FOR ENERGY, AEROSPACE AND BIOLOGICAL APPLICATIONS

Synthesis and Characterization of Conducting Polyaniline Nanostructured Thin Films for Solar Cell Applications BIJAN MEDI

,1,2 ALIREZA BAHRAMIAN,1 and VAHIDE NAZARI1

1.—Department of Chemical Engineering, Hamedan University of Technology, P.O. Box 65155579, Hamedan, Iran. 2.—e-mail: [email protected]

Optical-quality transparent, conducting polyaniline (PANI) thin films are suitable candidates for efficient counter electrodes for high-performance solar cells. In the first part of this work, the synthesis of highly uniform and homogenous nanostructured PANI films is reported. The film properties were assessed via scanning electron microscopy, atomic force microscopy, optical profilometry, spectrophotometry, and conductimetry. Simultaneous modeling, optimization and physical characterization of the PANI nanostructured films have not received much attention in the literature. Hence, in the second part, a multi-objective optimization approach with three objectives, namely minimum film thickness, maximum transparency, and maximum conductivity, was performed based on artificial neural network models with a novel k-fold cross-validation technique. The developed models can accurately predict the film characteristics in a wide range of design variables with most residuals remarkably less than 1.0%. Furthermore, after optimization, conductivity was increased three-fold ( 2.2 9 101 S/cm) at a good level of transparency ( 55%), which suit solar cell applications.

INTRODUCTION Electrically conductive polymer thin films are extensively used in numerous types of solar cells, such as perovskite,1 dye-sensitized,2 bifacial,3 and all-polymer4 architectures. The catalytic activity and transparency of conducting polymers are also important as they are supposed to substitute costly platinum-based and opaque carbon-based electrodes.5 Conducting polymers have typically good electrical and mechanical properties, and can be produced continuously as flexible films by chemical coating or electrochemical techniques. Polyaniline (PANI) is one of the most interesting conductive polymers with an electrical conductivity between 1 S/cm and 100 S/cm, and is used as a hole injection layer in thin films because of its good environmental stability and high structural resistance.6–8 The performance of PANI thin films in solar cells is affected by their thickness, optical transparency and stability, and electrical conductivity.9–11

(Received April 9, 2020; accepted August 26, 2020)

There has been a breakthrough in the modeling and analysis of the properties of nanostructured materials by first-principle models.12–15 These models intrinsically give rise to complex and nonlinear relationships between design variables and target characteristics of the conductive polymers. In computer simulations, these models require relatively cumbersome and time-consuming runs. Hence,