Solution-processed bulk heterojunction films

Janssen and coworkers have synthesized solution-processable conjugated oligomeric materials (221-222) combining electron-rich 2,5-dithienyl-N-dodecylpyrrole and electron-deficient 2,1,3-ben-zothiadiazole units. Bandgap of 1.60 and 1.46 eV was measured for thin films of 221 and 222, respectively. Bulk heterojunction realized with 221 and PCBM gave an efficiency of 0.34% [415]. 

However, only small changes have a pronounced impact on the morphology of bulk heterojunction thin films as well as their charge carrier separation and transportation. This in turn influences the photovoltaic properties of the small molecule-based bulk heterojunction devices. Solution-processed organic solar cells based on the molecules with the shortest methyl end groups exhibit a high short circuit current and fill factor (128). 

---