Highly Efficient Perovskite Solar Cells Employing an Easily Attainable Bifluorenylidene-Based Hole-Transporting Material

Abstract

The 4,4′-dimethoxydiphenylamine-substituted 9,9′-bifluorenylidene (KR216) hole transporting material has been synthesized using a straightforward two-step procedure from commercially available and inexpensive starting reagents, mimicking the synthetically challenging 9,9′-spirobifluorene moiety of the well-studied spiro-OMeTAD. A power conversion efficiency of 17.8 % has been reached employing a novel HTM in a perovskite solar cells.