Synergistic Effect of Processing Additives and Optical Spacers in Bulk‐Heterojunction Solar Cells

Processing a bulk-heterojunction (BHJ) solar cell with a narrow-bandgap polymer (P1) and a fullerene (PC71BM) results in a smooth surface morphology, and better performance is observed when a 1-chloronaphthalene solvent additive is used. The smooth surface enables the introduction of a titanium suboxide (TiOx) optical spacer between the BHJ layer and the electrode, which increases light absorption by redistributing the light intensity. TiOx incorporation leads to increases in the power conversion efficiency and device lifetime. Detailed facts of importance to specialist readers are published as ”Supporting Information”. Such documents are peer-reviewed, but not copy-edited or typeset. They are made available as submitted by the authors. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.