Inkjet-printing of hybrid transparent conducting electrodes for organic solar cells

We developed metal-grid hybrid transparent conducting electrodes (TCEs) by combining a metal grid with a conducting polymer. Metal-grid hybrid TCEs were prepared by inkjet-printing with both PEDOT: PSS and Ag nanoparticle inks and applied to the fabrication of organic solar cells (OSCs) instead of indium tin oxide (ITO). The electrical and optical properties of the metal-grid hybrid TCEs were optimized by modulating the Ag grid's line-to-line spacing (pitch). With a Ag-grid pitch of 1 mm, the metal-grid hybrid TCEs exhibited a sheet resistance of 10.3 Omega sq(-1) and an optical transmittance of 73% which represented <= 10% reduction when compared to the optical transmittance of inkjet-printed PEDOT: PSS films without Ag grids. Ag covering factor (ACF) was defined using the geometry of the Ag-grid and incorporated in a theoretical model to calculate the electrical and optical properties of the inkjet-printed metal-grid hybrid TCEs. It was found that the experimental values of the TCEs' electrical and optical properties were in good agreement with the calculation results based on the ACF-incorporated theoretical model. OSCs fabricated with the metal-grid hybrid TCEs showed a power-conversion cell efficiency comparable to those of conventional OCSs using ITO. This indicates that the inkjet-printed metal-grid hybrid TCE is a promising replacement for ITO to realize cost-effective OSCs. (C) 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim