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High-Performance Regular Perovskite Solar Cells Employing Low-Cost Poly(ethylenedioxythiophene) as a Hole-Transporting Material

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ABSTRACT

Herein, we successfully applied a facile in-situ solid-state synthesis of conducting polymer poly(3,4-ethylenedioxythiophene) (PEDOT) as a HTM, directly on top of the perovskite layer, in conventional mesoscopic perovskite solar cells (PSCs) (n-i-p structure). The fabrication of the PEDOT film only involved a very simple in-situ solid-state polymerisation step from a monomer 2,5-dibromo-3,4-ethylenedioxythiophene (DBEDOT) made from a commercially available and cheap starting material. The ultraviolet photoelectron spectroscopy (UPS) demonstrated that the as-prepared PEDOT film possesses the highest occupied molecular orbital (HOMO) energy level of −5.5 eV, which facilitates an effective hole extraction from the perovskite absorber as confirmed by the photoluminescence measurements. Optimised PSC devices employing this polymeric HTM in combination with a low-cost vacuum-free carbon cathode (replacing the gold), show an excellent power conversion efficiency (PCE) of 17.0% measured at 100 mW cm−2 illumination (AM 1.5G), with an open-circuit voltage (Voc) of 1.05 V, a short-circuit current density (Jsc) of 23.5 mA/cm2 and a fill factor (FF) of 0.69, respectively. The present finding highlights the potential application of PEDOT made from solid-state polymerisation as a HTM for cost-effective and highly efficient PSCs.

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(a) Photographs of monomer DBEDOT and PEDOT prepared on glass substrates. (b) Optical microscopy images of monomer DBEDOT (left) and PEDOT (right) formed from solid-state synthesis (magnification 200x). (c) SEM image of the surface of PEDOT fabricated from solid-state synthesis. (d) XRD spectra of monomer DBEDOT (black) and PEDOT fabricated from in-situ polymerisation method (red) on glass substrates.
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f2: (a) Photographs of monomer DBEDOT and PEDOT prepared on glass substrates. (b) Optical microscopy images of monomer DBEDOT (left) and PEDOT (right) formed from solid-state synthesis (magnification 200x). (c) SEM image of the surface of PEDOT fabricated from solid-state synthesis. (d) XRD spectra of monomer DBEDOT (black) and PEDOT fabricated from in-situ polymerisation method (red) on glass substrates.

Mentions: DBEDOT (Fig. 1) was chosen as the solid-state polymerisable monomer for the synthesis of conducting polymer PEDOT. DBEDOT was synthesized via a common bromination method from a commercially available and cheap starting material 3,4-ethylenedioxythiophene (EDOT) as reported previously45, which was confirmed by 1H NMR spectroscopy (Figure S1, Supporting Information (SI)). Conducting polymer PEDOT was subsequently prepared through an in-situ solid-state polymerisation of DBEDOT analogous to a reported method4546. The schematic solid-state synthesis route is presented in Fig. 1. Monomer DBEDOT was incubated at 80 °C for 4 h in a closed vial, during which period the color of the material changed from white to dark blue in the state of thin films (Fig. 2a). It indicates that the annealing process facilitated the transformation of monomer DBEDOT to polymer PEDOT. In Fig. 2b, the optical microscopy images clearly show that the colorless needle-shaped crystals of DBEDOT was transformed to black crystals of PEDOT. Scanning electron microscopy (SEM) image of the surface of PEDOT fabricated from solid-state synthesis is presented in Fig. 2c. The transformation of DBEDOT to polymer PEDOT was further confirmed by x-ray diffraction (XRD), as shown in Fig. 2d. The crystalline DBEDOT thin film shows main diffraction peaks at 2θ = 8.5, 16.8, 25.4, 27.0 and 34°. By stark contrast, a strong and sharp (line width ca. 0.2°) diffraction peak at 2θ = 30° was observed for the PEDOT thin film sample, which obviously do not belong to the DBEDOT and must be attributed to the structure of the formed polymer45.


High-Performance Regular Perovskite Solar Cells Employing Low-Cost Poly(ethylenedioxythiophene) as a Hole-Transporting Material
(a) Photographs of monomer DBEDOT and PEDOT prepared on glass substrates. (b) Optical microscopy images of monomer DBEDOT (left) and PEDOT (right) formed from solid-state synthesis (magnification 200x). (c) SEM image of the surface of PEDOT fabricated from solid-state synthesis. (d) XRD spectra of monomer DBEDOT (black) and PEDOT fabricated from in-situ polymerisation method (red) on glass substrates.
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Related In: Results  -  Collection

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f2: (a) Photographs of monomer DBEDOT and PEDOT prepared on glass substrates. (b) Optical microscopy images of monomer DBEDOT (left) and PEDOT (right) formed from solid-state synthesis (magnification 200x). (c) SEM image of the surface of PEDOT fabricated from solid-state synthesis. (d) XRD spectra of monomer DBEDOT (black) and PEDOT fabricated from in-situ polymerisation method (red) on glass substrates.
Mentions: DBEDOT (Fig. 1) was chosen as the solid-state polymerisable monomer for the synthesis of conducting polymer PEDOT. DBEDOT was synthesized via a common bromination method from a commercially available and cheap starting material 3,4-ethylenedioxythiophene (EDOT) as reported previously45, which was confirmed by 1H NMR spectroscopy (Figure S1, Supporting Information (SI)). Conducting polymer PEDOT was subsequently prepared through an in-situ solid-state polymerisation of DBEDOT analogous to a reported method4546. The schematic solid-state synthesis route is presented in Fig. 1. Monomer DBEDOT was incubated at 80 °C for 4 h in a closed vial, during which period the color of the material changed from white to dark blue in the state of thin films (Fig. 2a). It indicates that the annealing process facilitated the transformation of monomer DBEDOT to polymer PEDOT. In Fig. 2b, the optical microscopy images clearly show that the colorless needle-shaped crystals of DBEDOT was transformed to black crystals of PEDOT. Scanning electron microscopy (SEM) image of the surface of PEDOT fabricated from solid-state synthesis is presented in Fig. 2c. The transformation of DBEDOT to polymer PEDOT was further confirmed by x-ray diffraction (XRD), as shown in Fig. 2d. The crystalline DBEDOT thin film shows main diffraction peaks at 2θ = 8.5, 16.8, 25.4, 27.0 and 34°. By stark contrast, a strong and sharp (line width ca. 0.2°) diffraction peak at 2θ = 30° was observed for the PEDOT thin film sample, which obviously do not belong to the DBEDOT and must be attributed to the structure of the formed polymer45.

View Article: PubMed Central - PubMed

ABSTRACT

Herein, we successfully applied a facile in-situ solid-state synthesis of conducting polymer poly(3,4-ethylenedioxythiophene) (PEDOT) as a HTM, directly on top of the perovskite layer, in conventional mesoscopic perovskite solar cells (PSCs) (n-i-p structure). The fabrication of the PEDOT film only involved a very simple in-situ solid-state polymerisation step from a monomer 2,5-dibromo-3,4-ethylenedioxythiophene (DBEDOT) made from a commercially available and cheap starting material. The ultraviolet photoelectron spectroscopy (UPS) demonstrated that the as-prepared PEDOT film possesses the highest occupied molecular orbital (HOMO) energy level of −5.5 eV, which facilitates an effective hole extraction from the perovskite absorber as confirmed by the photoluminescence measurements. Optimised PSC devices employing this polymeric HTM in combination with a low-cost vacuum-free carbon cathode (replacing the gold), show an excellent power conversion efficiency (PCE) of 17.0% measured at 100 mW cm−2 illumination (AM 1.5G), with an open-circuit voltage (Voc) of 1.05 V, a short-circuit current density (Jsc) of 23.5 mA/cm2 and a fill factor (FF) of 0.69, respectively. The present finding highlights the potential application of PEDOT made from solid-state polymerisation as a HTM for cost-effective and highly efficient PSCs.

No MeSH data available.


Related in: MedlinePlus