Although the binary all-PSCs have abundant progress, the narrow absorption range of blend active layer hinders the device performance. With better sunlight absorption and charge carrier transfer, ternary PSCs using two donors and an acceptor or a donor and two acceptors have been extensively researched and obtained many encouraging advances.
Now, researchers in Southern University of Science and Technology and Peking University fabricated an efficient ternary all-PSCs by introducing a chlorinated polymer donor named PBClT as an additional donor into PTB7-Th and NDP-V-C7 blend films. The binary all-PSCs using PBClT has a moderate PCE of 6.44%, but the VOC is rather high, up to 0.93 V.
The PBClT and PTB7-Th are belonging to well-known PTB family polymers with TT and BDT units, they have very similar structure, and could form a kind of intimate complex like “polymer alloy” in blend films because they are analogs and have good compatibility from the film morphology. With the optimizing of PBClT contents, the chlorinated ternary all-PSCs pushed the PCE to 9.03%. The enhanced performance ascribed increased VOC and FF due to enhanced build-in potential and morphology via importing PBClT.
The results indicate that ternary approach, especially using polymer analogs with different absorption peaks as codonors, is an effective measurement to boost the PCE of all-PSCs. It will give very similar polymer morphology packing in binary system with broad coverage of the sunlight resource. The paper describing this work was published on Nov. 9 in Science China Chemistry.