1. Nafion-Modified PEDOT:PSS/c-Si Solar Cells
The 77th JSAP
Autumn
Meeting
15p-P13-2
Nafion-Modified PEDOT:PSS/c-Si Solar Cells
Graduate School of Science and Engineering, Saitama University, Saitama , Japan
Qiming Liu, Jaker Hossain, Takuya Miura, Koji Kasahara,
Daisuke Harada, Ryo Ishikawa, Keiji Ueno, and Hajime Shirai
We demonstrate the chemistry of amphiphilic perfluorosulfonic copolymer Nafion coated conductive poly(3,4-ethyelenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) and its effect on the photovoltaic performance of PEDOT:PSS/c-Si heterojunction solar cells. Solution-processed Nafion-coated PEDOT:PSS/c-Si heterojunction solar cells exhibit a power conversion efficiency of 14.0% with better stability for light soaking rather than that of the pristine PEDOT:PSS/c-Si device by adjusting the layer thickness of Nafion. These results originate from the chemical stability of fluorocarbon backbone of Nafion, diffusivity of silver paste into Nafion and contact with PEDOT:PSS, and Nafion as an antireflection layer.
Methods and Results
Characteristics: SE, XPS, SEM, Raman
Highly hydrophobic
fluorocarbon backbone
(Left) Optical model used for the spectra analysis including best fitted results. (Right) The n and k spectra of bulk component of bottom PEDOT:PSS layer, PEDOT:PSS-Nafion intermixing layer, and top Nafion layer, respectively of a typical 2wt% Nafion-coated PEDOT:PSS thin films. Ag
Nafion modified
PEDOT:PSS
InGa
C-Si
Hydrophilic -SO3-
Device Schematic Molecular Structure
PSS
PEDOT
Nafion
Modified
(a) Depth profile of XPS S(2p) core level spectra of 2 wt% Nafion-coated PEDOT:PSS films. (b) Raman spectra of Nafion-coated PEDOT:PSS thin films with different Nafion concentrations. (c,d) Cross sectional SEM images of Nafion/PEDOT:PSS/c-Si and Ag/Nafion/PEDOT:PSS/c-Si solar cell structures.
(Left)J-V curves of PEDOT:PSS/c-Si heterojunction solar cells with and without Nafion coating. (Right)J-V curves of Nafion-doped PEDOT:PSS/ c-Si heterojunction solar cells with different concentrations.
(a)
(b)
Quinoid
Benzoid
Stability of the J-V curves of (Left) Pristine and (Right) 2wt% Nafion-coated PEDOT:PSS/c-Si heterojunction solar cells for light soaking under AM1.5 simulated solar light exposure.
Conclusions: The photovoltaic performance of Nafion modified PEDOT:PSS/c-Si devices exhibit a higher efficiency of 14.0% with increasing Jsc up to 32.7 mA/cm2 and an improved stability for light soaking. These findings originate from following contributions: 1) Increased carrier mobility due to the extension of π-conjugation of PEDOT, 2) The resistance of the moisture and impurity due to Nafion layer, 3) Nafion over layer acts as an antireflection layer and 4) Silver paste as a top grid electrode diffuse and/or preferentially dissolved with Nafion, resulting in a good contact with underneath PEDOT:PSS.
Acknowledgements: Q. Liu appreciates the financial support by the Sasakawa Scientific Research Grant.