Toward High Performance Photovoltaic Cells based on Conjugated Polymers
Technical Report,16 Sep 2015,15 Sep 2016
NATIONAL CHIAO TUNG UNIV HSINCHU (TAIWAN) CHIAO TUNG Taiwan
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In the pursuit of high photon-to-electron conversion efficiency of organics photovoltaics, different approaches have been used, such as designing and synthesizing organic molecules with different energy band gap and good packing order for the active layers or constructing tandem devices. In the present study, we adopted a simple concept involving ternary blends that comprises a small amount of a high bandgap small molecule with a molecular structure that was structured to have energy transfer, a low band-gap polymer with good packing order as the active layer for a single-junction photovoltaic device. The light absorptions for the small molecule and the polymer are complementary for enhancing the absorption of the solar spectrum while their energy bands are offset structure for facilitating charge separation. We synthesize the SM-4OMe small molecule and chose the PTB7-Th polymer and blend them with fullerene for being used as active layers to demonstrate our approach. We found that the power conversion efficiency of the device that incorporates a ternary blend of PTB7-ThSM-4OMePC71BM 0.90.11.5 by weight as the active layer that was processed with 2 vol di-iodine octane DIO with chlorobenzene CB increased to 10.4 from 8 for the device incorporating PTB7-thPC71BM 11.5 weight active layer that was processed in a similar way, an increase of 30. This enhancement can be reasonably attributed to the energy transfer from the high band-gap small molecule SM-4OMe to the low band-gap polymer and optimum phase-separated morphology that is owing to a partial mixing of PTB7-th with SM-4OMe because of pi-pi stacking interaction between them since both of them were constructed with the same donor units, BDT.
- Polymer Chemistry
- Electrooptical and Optoelectronic Devices