High Performance Polymer Solar Cells Based On Metallic Film Substrate

Polymer solar cells have the advantages such as wide sources of raw materials,solution-processed manufacturing technology, ease of roll-to-roll large areafabrication and installation, et al. So they have broad prospects in practical application.But most polymer researches are still based on ITO transparent electrode, whichcontains expensive indium elements, needs expensive manufacturing equipment,complex preparation process.These will weaken polymer solar cells’ advantages oflow cost, limit the commercialization prospects in the future. This article has mainlycarried on the study of the alternative to indium doped tin oxide (ITO) transparentelectrode and the preparation of high performance polymer solar cells based on themetal substrate, which provide a new avenue to the realization of high performanceITO-free devices.Firstly, I have systematicly summarized the realization ways to ITO-freepolymer solar cell devices, analyzed the advantages and disadvantages of these ways,and decided to prepare high performance polymer solar cells based on metal filmtransparent electrode. Cu film was selected by simulation of the distribution ofoptical-electric field, short current density, transparency and reflection of the devicesusing Cu&Ag transparent film, these results turned out that the performance of Cudevices was higher than that of Ag devices.Secondly, we optimized the thickness of Cu to15nm, which had thetransparency of77%between300~800nm wavelength. Its roughness was loweredand the work function was down from4.68eV to4.34eV by inserting a PFN layer.We fabricated four devices separately, and their performances were shown as follows:Cu devices (Voc:0.74V, Jsc:7.2mA/cm2, PCE:2.8%), Cu-PFN devices (Voc:0.93V,Jsc:7.4mA/cm2, PCE:3.6%), ITO devices (Voc:0.63V, Jsc:9.7mA/cm2, PCE:3.1%),ITO-PFN devices (Voc:0.92V, Jsc:9.8mA/cm2, PCE:5.0%). The results showed thatVocof Cu-based and ITO-based devices with PFN had been improved greatly. Itproved that the electron-extract barrier between electrode and active layer was lowered and better interface contacts had been achieved, which were advantageous tothe electron collection.Finally, we verified that different performances between devices were due to thedifferences of the transparency, absorption of the transparent electrodes, theoptical-elcetric field, recombination mechanisms and carriers lifetime in the devicesby optical simulation, transient photo-voltage, EQE measurement.