Sulfonate Poly(aryl ether sulfone)-Modified PEDOT:PSS as Hole Transport Layer and Transparent Electrode for High Performance Polymer Solar Cells

Polymer solar cells (PSCs) with high short current density (<i>J</i>_sc) have been fabricated through a facile way by using a low-cost polyelectrolyte-modified poly­(3,4- ethylenedioxythiophene):poly­(styrenesulfonate) (PEDOT:PSS, P VP Al 4083) bilayer film as anode buffer layer. Spin-coating a layer of sulfonate poly­(aryl ether sulfone) (SPES) on the surface of PEDOT:PSS hole-transporting layer (HTL) is found to dramatically improve the <i>J</i>_sc value even up to 21.66 mA cm^–2. The notable <i>J</i>_sc is demonstrated to be correlated with interaction between the SPES and PEDOT, which removes the insulator of PSS with formation of continuous PEDOT domains, consequently leading to the improved conductivity and more imitate interfacial contact. It should be noted that the notable <i>J</i>_sc also partly results from the effect of a second anode due to the high conductivity of SPES-modified PEDOT:PSS. Through systematically investigation on a series of devices with different areas, it can be found that a real effective area of the devices should be carefully addressed to exclude the effect of a second anode, especially when a highly conductive interfacial material is incorporated. More interestingly, apart from the successful application in HTL, SPES also works well as transparent electrode. Compared with the pristine PEDOT:PSS (PH1000) anode, SPES-modified PH1000 as transparent anode achieves a dramatically increased performance in the ITO-free PSCs together with overall improved parameters, even equal to the one based on ITO anode. These findings indicate that solution-processed SPES shows a great potential in the fabrication of highly efficient PSCs as well as large-area, flexible printable PSCs

High-Performance Polymer Solar Cells Realized by Regulating the Surface Properties of PEDOT:PSS Interlayer from Ionic Liquids

Significant efforts have been dedicated to the interface engineering of organic photovoltaic device, suggesting that the performance and aging of the device are not only dependent on the active layer, but also governed by the interface with electrodes. In this work, controllable interfacial dipole and conductivity have been achieved in ionic liquids (ILs) modified poly­(3,4-ethylenedioxythiophene):poly­(styrenesulfonate) (PEDOT:PSS). We conclude that an appropriate interfacial conductivity is as essential as the suitable work function for an efficient buffer layer. Through forming favorable dipoles for hole transportation and reducing the film resistance by [HOEMIm]­[HSO4] treatment, an averaged performance of 8.64% is obtained for OPVs based on PTB7:PC71BM bulk heterojunction with improved stability. However, the improvement of performance is inconspicuous for OPVs based on PTB7-Th:PC71BM bulk heterojunction due to the incompetent energy level of high concentration ILs-modified PEDOT:PSS. The enhanced in-plane conductivity will reduce shunt resistance, and produce a fake high short-circuit current density (<i>J</i>_sc) with a lower fill factor. We point out that the <i>J</i>_sc can be improved by decreasing series resistance; meanwhile, the accompanying reduced shunt resistance has an unfavorable effect on device performance