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.
Highlights
Conducting polymers constitute another major class of organic HTMs in perovskite solar cells (PSCs)
PSCs employing this polymeric HTM show an impressive power conversion efficiency (PCE) of 17.0% measured at 100 mW cm−2 illumination (AM 1.5G), which is one of the highest reported value for conducting polymer-based HTMs
DBEDOT was synthesized via a common bromination method from a commercially available and cheap starting material 3,4-ethylenedioxythiophene (EDOT) as reported previously[45], which was confirmed by 1H NMR spectroscopy (Figure S1, Supporting Information (SI))
Summary
Conducting polymers constitute another major class of organic HTMs in PSCs. A number of conducting polymers have been used as HTMs in PSCs. Other type of thiophene-based conducting polymers have been tested as HTMs in PSCs, exhibiting poor efficiencies below 10%27,33–35. High overall efficiencies of PSC devices based on polymeric HTMs have been rarely reported far. The high-performing polymeric HTMs reported so far typically require complicated synthesis, especially for the monomers (tedious synthesis and high purity required), resulting in high production costs. We report facile solid-state synthesis of conducting polymer PEDOT as a HTM in mesoporous PSCs based on a (FAPbI3)0.85(MAPbBr3)0.15 light absorber. PSCs employing this polymeric HTM show an impressive PCE of 17.0% measured at 100 mW cm−2 illumination (AM 1.5G), which is one of the highest reported value for conducting polymer-based HTMs. The present finding highlights the potential application of PEDOT made from solid-state synthesis as a HTM for cost-effective and high-performing PSCs
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