Pulsed Light-induced Thermal Stabilization of π-conjugated Polymers in a Roll-to-Roll Process...
Polymer solar cells (PSCs) are recognized as one of the most promising candidates for low cost solar cells because of the possibility of a fast roll‐to‐roll coating (R2R) production on flexible and large-area substrates by solution processing of polymer inks. Low-bandgap polymers blended with a soluble fullerene derivative has proven that they can provide highly efficient light harvesting across a broad area of the solar spectrum resulting in power conversion efficiencies over 8% at present. To warrant solubility during solution processing solubilizing chains are incorporated on the polymer backbone and if the chains are designed as thermally cleavable they can be removed in a post-processing heating step to ensure insolubility and high photochemical stability of the polymer. Though high temperatures are required for thermocleaving (∼200 °C) and most relevant plastic substrates for PSCs will not support these temperatures. Thermocleaving in a R2R process is a key issue needed to be solved in order to bring the PSC technology to the next level.
Schematic drawing of the potential R2R processing setup. A thermally reactive polymer/fullerene ink is coated from solution and the deposited film is subsequently thermocleaved by a high energy flashlamp resulting in a more robust material. The final device architecture of a PSC is also shown
This research project will focus on the development of a R2R processing technique, using high energy flash light, for selective heating of the polymer layer in contact with a heat sensitive substrate. The research builds on several areas including molecular design, organic synthesis and advanced processing techniques. Fast and efficient thermocleaving in a full R2R process on flexible plastic substrates is essential in order to bring commercial PSCs closer to its realization. Thus, the success of the proposed research project will be a corner stone for the efforts of establishing a Danish solar cell production directed towards bulk electricity production.