Innovative Incorporation of Poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) as Hole Carrier Transport Layer and as Anode for Organic Solar Cells Performance Improvement.

Leon Hamui,Maria Elena Sánchez-Vergara,Ricardo Corona-Sánchez,Omar Jiménez-Sandoval,Cecilio Álvarez-Toledano

doi:10.3390/polym12122808

Abstract

In this work, we present a comparative study of benzoid poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT:PSS) as electrode and as hole carrier transport layer (HTL) in the manufacture of organic photovoltaic devices using Fischer metal-carbene complexes. The performance of the different devices was evaluated for solar cell applications. Scanning electronic microscopy (SEM) and X-ray diffraction (XRD) were used to characterize the thin films that integrated the devices. A more ordered and crystallized active film microstructure is observed when using benzoid PEDOT:PSS as nucleation layer. The optical gap for both direct and indirect electronic transitions was evaluated from ultraviolet-visible spectroscopy data (UV-vis), as well as the absorption coefficient (α), and the values are in the range of 2.10–2.93 eV. Photovoltaic devices with conventional architecture, using two different chromium carbenes as active layers, were manufactured, and their electrical behavior was studied. The devices were irradiated with different wavelengths between the infrared and ultraviolet regions of the electromagnetic spectrum. Using the PEDOT:PSS film as hole carrier transport layer (HTL) decreases the slope on the ohmic and space charge limited current (SCLC) regions and eliminates the trap-charge limited current (T-CLC) mechanism. Furthermore, a saturation current of ~1.95 × 10−10 A and higher current values ~1.75 × 10−2 A at 4 V, ~4 orders in magnitude larger were observed. The PEDOT:PSS films as HTL in the devices reduced the injection barrier, thus showing a better performance than as anodes in this type of organic solar cells.

Highlights

A photovoltaic cell is a device that converts sunlight into electricity using semiconductor materials [1]
The films deposited on PEDOT:PSS (Figure 2c,d) show a flake-like morphology [42], the films are more homogeneous and the number of hollows decreases with respect to the films deposited on indium tin oxide (ITO); the same occurs with the carbenes particle size
If the transport of charges is more efficient in films with ordered structures, a better electrical behavior can be expected in devices made with PEDOT:PSS films

Summary

Introduction

A photovoltaic cell is a device that converts sunlight into electricity using semiconductor materials [1]. Polymers 2020, 12, 2808 absorption coefficients, which make them good chromophores for optoelectronic applications [2,3]. Another important optoelectronic characteristic in organic semiconductors is the fact that their electronic band gap can be engineered by chemical synthesis [2]. Group 6 Fischer metal-carbene complexes are an example of the above; depending on the metal, the functional group or the substituent found in the molecular structure is the charge transfer capacity and in general, the optoelectronic properties that the carbene presents [4,5,6,7,8,9,10,11,12,13,14]. Organic semiconductors can be classified into two classes: molecular semiconductors (MSCs), like the Fischer metal-carbene complexes, and π-conjugated polymers [14]

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