Networked Conductive Polythiophene/Polyaniline Bottlebrushes with Modified Carbon Nanotubes As Hole Transport Layer in Organic Photovoltaics
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Three types of hole transport layers (HTLs) were developed based on multi-walled carbon nanotubes (CNTs), including pure CNT thin films, CNT:poly(3-thiophene ethanol) (P3ThEt)-g-polyaniline (PANI) nanocomposites, and CNT-g-poly(3-dodecyl thiophene) (PDDT):P3ThEt-g-PANI interconnected networks, and utilized in poly[benzodithiophene-bis(decyltetradecyl-thien) naphthothiadiazole] (PBDT-DTNT):phenyl-C61-butyric acid methyl ester (PC61BM) and poly[bis(triiso-propylsilylethynyl) benzodithiophene-bis(decyltetradecyl-thien) naphthobisthiadiazole] (PBDT-TIPS-DTNT-DT):PC61BM solar cells. Pure CNTs were not the appropriate candidates for application instead of conventional poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) HTLs. To tackle this issue, the CNT:P3ThEt-g-PANI and CNT-g-PDDT:P3ThEt-g-PANI films were focused with thicknesses of 10 nm and 20 nm. The prominent characteristics peaked at 20-nm thin films of CNT-g-PDDT:P3ThEt-g-PANI, demonstrating the largest power conversion efficiencies (PCE) of 5.65 (12.84 mA/cm2, 62%, and 0.71 V) and 4.80% (11.59 mA/cm2, 60%, and 0.69 V) in the BDT-DTNT and PBDT-TIPS-DTNT-DT based devices, respectively. The CNT-g-PDDT:P3ThEt-g-PANI thin films which possess an interconnected network, composed of grafted-CNTs and P3ThEt-g-PANI bottlebrushes, were proper alternatives for conventional PEDOT:PSS HTLs and warranted the superior photovoltaic results by smooth morphologies (root mean square = 1.0–1.1 nm) and low sheet resistance (2.2–8.3 × 104 Ω/sq). The corresponding systems without grafting of CNT precursors were the second categories of well-functioned HTLs (3.13–4.04%) and had somehow decreased physical and photovoltaic properties.
KeywordsHTL CNT polythiophene PANI PCE
Project funded by China Postdoctoral Science Foundation, the Electronic Fence System project, the Project of FDCT, and the Project of the Macao Foundation.
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