An investigation was carried out into the effect of uniaxial optical anisotropy in poly(3,4-ethylenedioxythiophene):poly(styrenesulfonic acid) (PEDOT:PSS) on the photovoltaic performance of crystalline Si/PEDOT:PSS heterojunction solar cells fabricated by spin coating using either a methanol (MeOH) solvent alone or using MeOH and ethylene glycol (EG) as cosolvents. Spectroscopic ellipsometry revealed that the extraordinary index of refraction increased by the use of the cosolvents. In contrast, the ordinary index of refraction indicated metallic properties and was almost independent of the concentration of MeOH or EG. The highest conductivity was found for a (PEDOT:PSS):(MeOH):(EG) weight ratio of 1:1:0.1, and this sample exhibited a relatively high power conversion efficiency of 11.23%. These findings suggest that the increase in the extraordinary index of refraction leads to an enhancement of the hole mobility in PEDOT:PSS, resulting in improved photovoltaic performance.

Real-time monitoring of optical anisotropy during growth by the chemical mist deposition of poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) films was carried out using spectroscopic ellipsometry. The microstructure of the grown films was found to be primarily determined by the DC bias applied to the mesh electrode. The ellipsometry results revealed that uniaxial anisotropy appeared for film thicknesses of about 5 nm and above, which corresponds to the average size of PEDOT crystallites. The extraordinary refractive index was found to be strongly correlated with the carrier mobility. Both the degree of optical anisotropy and the carrier mobility could be controlled during film growth by adjusting the DC bias.

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We investigated the graphene oxide (GO) based n-type crystalline silicon (c-Si)/conductive poly(ethylene dioxythiophene):poly(styrenesulfonate)(PEDOT:PSS) Schottky junction devices with optical characterization and carrier transport measurement techniques. The optical transmittance in the UV region decreased markedly for the films with increasing the concentration of GO whereas it increased markedly in the visible-infrared regions. Spectroscopic ellipsometry revealed that the ordinary and extraordinary index of refraction increased with increasing the concentration of GO. The hole mobility also increased from 1.14 for pristine film to 1.85 cm2/V s for the 12–15 wt. % GO modified film with no significant increases of carrier concentration. The highest conductivity was found for a 15 wt. % GO modified PEDOT:PSS film: the c-Si/PEDOT:PSS:GO device using this sample exhibited a relatively high power conversion efficiency of 11.04%. In addition, the insertion of a 2–3 nm-thick GO thin layer at the c-Si/PEDOT:PSS interface suppressed the carrier recombination efficiency of dark electron and photo-generated hole at the anode, resulting in the increased photovoltaic performance. This study indicates that the GO can be good candidates for hole transporting layer of c-Si/PEDOT:PSS Schottky junction solar cell.

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The above article, published online on 25 July 2012 in Wiley Online Library (http://wileyonlinelibrary.com), has been retracted by agreement between the authors, the journal Editor‐in‐Chief, Stefan Hildebrandt, and Wiley‐VCH GmbH & Co. KGaA. The retraction has been agreed since the contents of the article have already been published by the corresponding author in Jpn. J. Appl. Phys. 51, 061602 (2012) on 4 June 2012. The manuscript submitted to physica status solidi (c) was part of the E‐MRS 2012 Spring Meeting, Symposium A, Proceedings. The authors regret the dual publication and express their sincere apologies to readers.

The above article, published online on 25 July 2015 in Wiley Online Library (http://wileyonlinelibrary.com), has been retracted by agreement between the authors, the journal Editor‐in‐Chief, Stefan Hildebrandt, and Wiley‐VCH GmbH & Co. KGaA. The retraction has been agreed since the contents of the article have already been published by the corresponding author in Jpn. J. Appl. Phys. 51, 061602 (2015) on 4 June 2015. The manuscript submitted to physica status solidi (c) was part of the E‐MRS 2015 Spring Meeting, Symposium A, Proceedings. The authors regret the dual publication and express their sincere apologies to readers. (© 2015 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Electrospray-deposited poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) was investigated using several solvent solutions as a hole-transporting layer for spin-coated poly(3-hexylthiophene-2,5-diyl):[6,6]-phenyl-C61 butyric acid methyl ester (P3HT:PCBM) mixture organic thin-film solar cells (OSCs). Among them, the uniform deposition of PEDOT:PSS films was realized using 70% N,N-dimethylformamide solvent solution. The P3HT:PCBM solar cells with electrospray-deposited PEDOT:PSS as a hole transport layer showed a relatively high performance with an open-circuit voltage V oc of 0.47 V, a short-circuit current J sc of 8.9 mA/cm2, a fill factor FF of 0.48, and a power conversion efficiency of 2.0%, which were almost the same as those with a spin-coated PEDOT:PSS layer. These findings imply that the electrospray-deposited PEDOT:PSS is a possible material for use as a hole transport layer for conjugated polymer-based OSCs.