A research team at the Hong Kong University of Science and Technology (HKUST) has developed a family of polymer and fullerene materials that enables multiple high-efficiency polymer solar cells. The team, led by Prof He Yan of the Department of Chemistry, discovered a material design motif that led to three new polymers and over ten high-performance combinations yielding solar cell efficiencies of up to 10.8%, a new record for single-junction polymer solar cells.
Polymer solar cell technology is low cost and environmentally friendly, allowing solar panels to be produced using high throughput roll-to-roll printing methods similar to those used to print newspapers. Polymer solar panels are also light in weight and exhibit excellent mechanical flexibility and so can be used to charge mobile devices such as smart phones and laptop computers. Despite recent progress in the polymer solar cell field, several limitations have been holding back its development. For instance, the field lacked an effective approach to controlling the polymer:fullerene blend morphology that is critical to achieving high solar cell performance.
But Prof Yan and his team found that the temperature dependent aggregation properties of the polymers is the key to creating highly efficient polymer solar cells that can be mass produced relatively cheaply. These findings open the door to experimentation with different chemical mixtures that comprise the active layers of the cells. Prof Ade’s group specializes in characterizing polymer:fullerene morphology using various advanced X-ray techniques, and has found that the HKUST polymers enable a new “near-optimal” morphology that is distinctively different from that formed by previous state-of-the-art materials.
“Materials development efforts for polymer solar cells generally have low success rates, with limited choices of polymers and essentially only one fullerene yielding >9% cells,” Prof Yan comments. “Since we achieved our first 10% efficiency polymer in September 2013, we have applied our material design motif and developed two other polymers and numerous fullerene materials with great performance. We hope that our material development success and the morphological insights will inspire others to explore many more polymer:fullerene blends, further increasing the efficiency of solar cells, decreasing their production costs and leading to a commercially viable alternative source of energy.”