Subscriber access provided by University of Rhode Island | University Libraries
Article
Enhancing Efficiency and Durability of Inverted Perovskite Solar Cells with Phenol/Unsaturated Carbon-Carbon Double Bond Dualfunctionalized Poly(3,4-ethylenedioxythiophene) Hole Extraction Layer Yuda Li, Tiefeng Liu, Xueqing Qiu, Yinhua Zhou, and Yuan Li ACS Sustainable Chem. Eng., Just Accepted Manuscript • DOI: 10.1021/ acssuschemeng.8b04603 • Publication Date (Web): 01 Dec 2018 Downloaded from http://pubs.acs.org on December 1, 2018
Just Accepted “Just Accepted” manuscripts have been peer-reviewed and accepted for publication. They are posted online prior to technical editing, formatting for publication and author proofing. The American Chemical Society provides “Just Accepted” as a service to the research community to expedite the dissemination of scientific material as soon as possible after acceptance. “Just Accepted” manuscripts appear in full in PDF format accompanied by an HTML abstract. “Just Accepted” manuscripts have been fully peer reviewed, but should not be considered the official version of record. They are citable by the Digital Object Identifier (DOI®). “Just Accepted” is an optional service offered to authors. Therefore, the “Just Accepted” Web site may not include all articles that will be published in the journal. After a manuscript is technically edited and formatted, it will be removed from the “Just Accepted” Web site and published as an ASAP article. Note that technical editing may introduce minor changes to the manuscript text and/or graphics which could affect content, and all legal disclaimers and ethical guidelines that apply to the journal pertain. ACS cannot be held responsible for errors or consequences arising from the use of information contained in these “Just Accepted” manuscripts.
is published by the American Chemical Society. 1155 Sixteenth Street N.W., Washington, DC 20036 Published by American Chemical Society. Copyright © American Chemical Society. However, no copyright claim is made to original U.S. Government works, or works produced by employees of any Commonwealth realm Crown government in the course of their duties.
Page 1 of 24 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
ACS Sustainable Chemistry & Engineering
Enhancing Efficiency and Durability of Inverted Perovskite Solar Cells with Phenol/Unsaturated Carbon-Carbon Double Bond Dual-functionalized Poly(3,4ethylenedioxythiophene) Hole Extraction Layer Yuda Li†, Tiefeng Liu§, Xueqing Qiu*†,‡, Yinhua Zhou§, and Yuan Li*†,‡ †School
of Chemistry and Chemical Engineering, Guangdong Provincial Engineering
Research Center for Green Fine Chemicals, South China University of Technology, 381 Wushan Road, Tianhe District, Guangzhou, 510641, China ‡ State
Key Laboratory of Pulp and Paper Engineering, South China University of
Technology, 381 Wushan Road, Tianhe District, Guangzhou, 510641, China §Wuhan
National Laboratory for Optoelectronics, School of Optical and Electronic
Information, Huazhong University of Science and Technology, 1037 Luoyu Road, Hongshan District, Wuhan, 430074, China *E-mail:
[email protected] (Y. Li);
[email protected] (X. Qiu). Tel.: 86-2087114722. Fax: +86-20-87114721.
ABSTRACT: Lignosulfonate (LS) with lots of active phenol and unsaturated carboncarbon double bond groups is applied as template and dispersant to prepare PEDOT:LS complex which possesses some superior properties including high work function (WF), superior homogeneity and excellent waterproofness compared to the popular conducting
polymer,
poly(3,4-ethylenedioxythiophene):poly(styrene
sulfonate)
(PEDOT:PSS). The reactivity of phenol and unsaturated carbon-carbon double bond groups can result in a covalent bonding between LS and PEDOT improving the homogeneity of PEDOT:LS. The thermal crosslinking activity of phenol and unsaturated carbon-carbon double bond groups can result in a dense PEDOT:LS film
ACS Paragon Plus Environment
ACS Sustainable Chemistry & Engineering 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
with excellent waterproofness. Inspired by the aforementioned merits, PEDOT:LS is applied as hole extraction material (HEM) in inverted methylammonium-lead iodide perovskite solar cell (PSC).The PEDOT:LS-based PSC shows an enhanced power conversion efficiency (PCE) of 12.85%, outperforming the PEDOT:PSS reference device exhibiting a PCE of 12.10% owing to the enhanced WF and homogeneity of HEL. More importantly, the PEDOT:LS-based PSC shows a higher long-term stability compared with PEDOT:PSS reference device due to the excellent waterproofness of HEL. Our research provides a strategy for developing new template for conducting polymer based on lignin, a rich renewable biomass containing lots of active phenol and unsaturated carbon-carbon double bond groups. KEYWORDS: Crosslinkable conducting polymer; lignin; homogeneity; CH3NH3PbI3based PSCs; device stability INTRODUCTION The most widely used water-solution processable conducting polymer is poly(3,4ethylenedioxythiophene):polystyrene sulfonic acid (PEDOT:PSS). It commonly acts as hole extraction layer (HEL) or hole injection layer in normal organic optoelectronic devices. However, there still are some demerits for PEDOT:PSS: (1) the relatively low work function (WF) (4.8-5.1 eV) limit the hole extraction from or injection into adjacent functional layer;1 (2) the relatively inferior film homogeneity caused by the excess and free PSS insulator should result in an inefficient hole transport process;2 (3) the high hydrophilic nature and inferior waterproofness could degrade device stability.3 Recently, a plenty of efforts, e.g. additive treatment 4-7 and utilization of alternatives of PSS,8, 9 including our recent works,2, 3, 7, 10-12 have been made to improve the application performance of PEDOT film. These progresses, especially the development of alternatives of PSS, will encourage researchers to seek new template for fundamentally altering the nature and improving the property of aqueous PEDOT dispersions.
ACS Paragon Plus Environment
Page 2 of 24
Page 3 of 24 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
ACS Sustainable Chemistry & Engineering
Figure 1. Molecular structures of templates PSS and LS In the last decades, lignosulfonate (LS), a rich renewable resource, was mainly used in the field of chemical industry including dyestuff dispersants, coal water slurry dispersants, oil dispersants and concrete admixtures owing to its natures of environmentally friendly, well dispersity and pretty cheap.13 The molecular structures of templates PSS and LS are shown in Figure 1. In 2012, Inganas et al14 reported that the phenol group in lignin could storage charges and they utilized LS as dispersant to prepare polypyrrole conducting polymer and successfully applied in supercapacitor. Recently, we firstly reported the hole transporting property of LS and successfully applied LS and its derivatives as template and dispersant for PEDOT in organic electronics. 10, 11, 15 Especially, in PSC, using grafted sulfonated-acetone-formaldehyde lignin as the template and dispersant to prepare PEDOT HEL, we obtained an enhanced power conversion efficiency of 14.94%, outperforming the PEDOT:PSS reference device with a PCE of 12.6%.10 However, the previous works focused on the hole transporting and charge storage properties of LS and its derivatives. The reactivity of phenol and unsaturated carbon-carbon double bond groups in LS under oxidant and heating as well as the structural homogeneity and waterproofness of the LS doped PEDOT conducting polymer are ignored. Moreover, their device stabilities have not been investigated. In this work, LS was applied as template and dispersant to prepare PEDOT:LS conducting polymer. The crosslinking activity of phenol and unsaturated carbon-carbon double bond groups in LS during the oxidation polymerization process of EDOT as well as during the heat treatment process was systematically investigated by UV-vis, FTIR and GPC measurements. The resulted covalent bonding between LS and PEDOT
ACS Paragon Plus Environment
ACS Sustainable Chemistry & Engineering 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
during the oxidation polymerization process could improve the homogeneity of PEDOT:LS which was investigated by AFM and phase separation experiment. The crosslinking between LSs during heating process could result in a dense film with excellent waterproofness which was studied by contact measurement. Moreover, the properties including conductivity, electrochemical behaviour and WF of PEDOT:LS film were systematically studied and compared with that of PEDOT:PSS film. By taking advantages of the high WF, superior homogeneity and well waterproofness of PEDOT:LS, its application potential as HEL was evaluated in inverted methylammonium lead tri-iodide-based (MAPbI3-based) PSCs. EXPERIMENTAL SECTION Materials. 3,4-Ethylenedioxythiophene (EDOT) monomer was purchased from Sigma-Aldrich Co. Ammonium persulphate ((NH4)2S2O8, APS) oxidant was purchased from Sigma-Aldrich Co. Russian sodium lignosulfonate (LS) template was extracted from pine pulping liquor and purified by a dialysis membrane (molecular weight cutoff of 1000 Da ). PEDOT:PSS (CleviosTM P VP AI 4083, the weight ratio of PEDOT to PSS is 1:6) used for comparison was obtained from Hersbit Chemical Material Co. Ltd. The weight concentration of PEDOT:PSS aqueous dispersion was 1.0%. All other chemicals were analytical grade and used without further purification. Preparation of PEDOT:LS aqueous dispersion. LS, as template and dispersant, was used to prepare PEDOT:LS conducting polymer. The preparation procedure as follow: In a 50 mL conical flask 1.0 g of LS and 0.2 g of EDOT were mixed in 25 mL of deionized water and stirred vigorously at room temperature for 30 min. Then HCl (3 M) was added to adjust the pH of the mixture to 2 and 0.417 g of APS was added. This aqueous dispersion was stirred vigorously for 48 h and purified by a dialysis membrane (molecular weight cutoff of 1000) for five days. Subsequently, the obtained solution of PEDOT:LS was concentrated to about 1.0% by weight by rotary evaporation. Characterizations. FT-IR measurements were carried out on a Nicolet Avatar 320 FT-IR spectrophotometer. UV–vis spectra were measured by a UV-3100 UV–vis spectrophotometer. Molecular weight distributions were obtained by a Waters 1515 gel
ACS Paragon Plus Environment
Page 4 of 24
Page 5 of 24 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
ACS Sustainable Chemistry & Engineering
permeation chromatography (GPC) detector. Particle size distributions were obtained by a Brookhaven Zeta Potential Analyzer and pH values were measured by a Mettler Toledo LE410 pH probe. Film thicknesses were measured with a Dektak150 step profiler. Electrical conductivities were determined by using a RTS-9 four-point probe meter. Cyclic voltammetric (CV) studies were carried out in an electrolyte solution of 0.1 M tetrabutylammoniumhexa fluorophosphates (Bu4NPF6) by utilizing a three electrode system with ITO glass substrate coated with the polymer film as working electrode, Ag electrode as reference electrode, and Pt wire as counter electrode, respectively. Atomic force microscopy (AFM) images were obtained by a Park XE-100 instrument. Waterproofness of the PEDOT films were assessed by a JC2000C1 static contact angle instrument. Electron spin resonance (ESR) spectra were measured by a JES-FA200 spectrometer. Ultraviolet photoelectron spectroscopy (UPS) spectra were obtained by a Thermo Fisher VG Scienta R400 instrument. Raman spectra were recorded on a Thermo Fisher DXRTMxi spectrometer. Photographs were taken using iPhone 8. Fabrication and Characterization of inverted PSCs. Before fabrication, the indium tin oxide (ITO) glass substrates were sequentially rinsed by ultrasonication in detergent solution, water, acetone and ethanol. After drying at 130 °C for 15 min, the substrates were cleaned by oxygen plasma for 6 min. The HELs were obtained via spin-coating (2500 rpm, 1 min) the PEDOT aqueous dispersions onto the cleaned substrates, and then heated at 120 °C for 12 min. The MAPbI3 layer was then spin-coated (4000 rpm, 30 s) onto the surface of HEL via anti-solvent method from precursor solution, followed by baking at 100 °C for 5 min. The MAPbI3 precursor solution was prepared by stirring theγ-GBL/DMSO=7:3 (v/v) mixture containing MAI and PbI2 at 60 °C for 30 min. Afterwards, the PC60BM (20 mg ml-1 in chlorobenzene) and polyethylenimine (PEI, 0.1 wt.% in isopropanol) were sequentially spin-coated at 2000 rpm for 40 s and 5000 rpm for 60 s, respectively. Finally, silver cathode was thermally evaporated under high vacuum (
