The generation of electrical energy depending on renewable sources is rapidly growing and gaining serious attention due to its green sustainability. With fewer adverse impacts on the environment, the sun is considered as a nearly infinite source of renewable energy in the production of electrical energy using photovoltaic devices. On the other end, organic photovoltaic (OPV) is the class of solar cells that offers several advantages such as mechanical flexibility, solution processability, environmental friendliness, and being lightweight. In this research, we demonstrate the manufacturing route for printed OPV device arrays based on conventional architecture and using inkjet printing technology over an industrial platform. Inkjet technology is presently considered to be one of the most matured digital manufacturing technologies because it offers inherent additive nature and last stage customization flexibility (if the main goal is to obtain custom design devices). In this research paper, commercially available electronically functional inks were carefully selected and then implemented to show the importance of compatibility between OPV material stacks and the device architecture. One of the main outcomes of this work is that the manufacturing of the OPV devices was accomplished using inkjet technology in massive numbers ranging up to 1500 containing different device sizes, all of which were deposited on a flexible polymeric film and under normal atmospheric conditions. In this investigation, it was found that with a set of correct functional materials and architecture, a manufacturing yield of more than 85% could be accomplished, which would reflect high manufacturing repeatability, deposition accuracy, and processability of the inkjet technology.

We report on ITO-free OLEDS with a transparent hybrid Cu nanoparticle grid/PEDOT:PSS electrode processed in ambient conditions. An experimentally based methodology was implemented, where studies on alternative PEDOT:PSS derivatives and Cu grid design were performed, to gradually increase the efficiency of lab scale ITO-free OLEDs. To further increase electrode performance, inkjet-printed (IJP) Cu-grids are embedded to flatten the electrode, reduce leakage current and enhance homogeneity and efficiency. Finally, embedded Cu based ITO-free OLEDs showed current and power efficiencies comparable to reference ITO-based OLEDs. Methods to manufacture large area flat embedded IJP Cu-electrodes on glass and flexible substrates are presented and upscaling prospects of the proposed ITO-free electrode are discussed.

We investigate organic polymer/fullerene (P3HT/PCBM) bulk heterojunction solar cells by means of photoinduced absorption spectroscopy (PIA). The dynamic properties of the charge carriers are studied in the temperature range of 5 K to 200 K by recording the PIA signal in the frequency domain. The mobility and the lifetime of the positive polarons are de‐ termined. The dependence of the short circuit current on the incident light intensity is also investigated. Finally, the properties of annealed and not annealed solar cells are compared. As the most interesting result, the appearance of two polaron species on different time scales is observed. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)