Injection Molding Plastic Solar Cells

Abstract

While organic photovoltaics are accessing specific application sectors taking advantage of their unique properties, it is important to identify as many differentiators as possible to expand the market penetration and consolidation of this technology. In this work, for the first time, the large-scale fabrication of organic photovoltaic modules embedded into structural plastic parts through industrial injection molding is demonstrated. Thermoplastic polyurethane is chosen as the injected material to show that this additional processing step can yield flexible, lightweight photovoltaic modules with enhanced device robustness and virtually unchanged performance. The critical optomechanical and physico-chemical material properties, as well as the plastic processing parameters to enable in-mold plastic solar cells with improved performance and stability, are discussed and provided with perspective.

Keywords: in-molds; organic photovoltaics; plastic solar cells; solution-processing; upscaling electronics.

Figure 1

In‐line fabrication and characterization of organic photovoltaic modules. a) Outline of the complete single‐junction stack. b) Appearance of the Ag nanowires layer: (top) SEM top view image, (bottom) two close‐up photographs of Ag NWs layers on top of the front Ag grid, comparing a homogeneous coverage against bubbling formation. c) Pictures of the roll‐to‐roll fabrication of the photovoltaic modules. The processing techniques used include slot‐die coating, rotary screen printing, and flexography. d) Panoramic LBIC images of 330 modules measured with a contactless, in‐line characterization system.^{[ 22 ].}

Figure 2

Injection molding processing of OPV modules. a) Schematics of the injection molding process. b) The Engel COMBI Victory 1050H/200 W/200L injection molding machine used in this study. The inset shows close‐up photographs of the mold cavity holding an OPV module in a vertical (left) or horizontal (right) position. c) Statistical performance data taken from 32 injected modules. All data points are included (left); box range 25/75th percentiles (right). d) I–V characteristics of an OPV module before and after injection (see inset picture), showing no loss in performance. e) High‐resolution LBIC images of the module shown in (d) before IM (top) and after IM (bottom). The dashed red arrow indicates the direction of the injected molten polymer; the red solid arrows point to areas of the module that show degradation upon IM.

Figure 3

Mechanical stress and accelerated degradation testing. a) Photographs of control (left) and in‐mold (right) OPV module subjected to uniaxial tensile stress until delamination. b) I–V derived performance parameters of an IM‐OPV module as a function of bending cycles. c) Efficiency evolution of 2 modules subjected to accelerated photo‐stability degradation according to ISOS‐L‐3. d) Close‐up photographs of the degraded modules in (c), showing a much lower bubbling formation and yellow coloration on the IM‐OPV modules.