2, University of Erlangen-Nuremberg, Erlangen, , Germany
One of the biggest attractions of the organic photovoltaics (OPV) technology is the easiness with which it can be integrated. However, despite its semitransparency and wide variety of colours, a major unresolved challenge is to fabricate optically inconspicuous organic photovoltaic modules (OPV-M) that can be integrated into visually demanding products. This is dominantly due to the visual obstruction from Z-interconnection lines inherent to module processing with classical patterning methods. We now present for the first time a solution to this problem, which utilizes a visually seamless interconnection method to elegantly minimize the conspicuity of the interconnection regime. We realize such invisible interconnects by inkjet printing highly conductive silver lines or dots, which penetrate the solar cell stack and form an electrical connection between adjacent cells. Topographical and cross-sectional images of the interconnection region are taken to illustrate how the connection is formed. Photos of the modules are also provided to showcase the stark visual difference between the classical and the new approach implemented in this work. Beside the minimal power conversion efficiencies (PCE) loss when transferred from small (0.1 cm2) single cells to 3-cell solar modules (3 cm2), we also demonstrate the effective connection between cells by special measurement structures that can precisely measure the specific interconnection resistance down to 1.5 mΩcm2. Finite element (FEM) simulation further rationalizes the excellent electrical cell-to-cell connection established with this interconnection technology. We combine this technology with a variable-geometry module design into an innovative digital inkjet printing platform for the production of state-of-the art but visually attractive solar modules. The full potential of this concept is demonstrated by various fully inkjet printed semitransparent OPV-M portraits and logos with area over 84cm2 and efficiencies over 3.5%.