| 초록 |
In developing new conjugated organic materials for BHJ solar cells, alternatively composed of weak electron-donating and strong electron-accepting units has been utilized for high VOC. The introduction of electron-donating units with different aromatic resonance stabilization energy into the A-D-A type small molecule (SM), where A is thiophene-capped diketoppyrolopyrrole (TDPP) and D is an electron-donating unit such as thiophene (T) and phenylene (Ph), would precisely control HOMO energy levels of SMs. Therefore, a series of TDPP-based SMs, (TDPP)2, T(TDPP)2, and Ph(TDPP)2, were synthesized. HOMO energy level of T(TDPP)2 (-5.17 eV) is slightly higher than (TDPP)2 (-5.19 eV) due to a strong electron-donating thiophene bridge, while HOMO energy level of Ph(TDPP)2 (-5.28 eV) is deeper than (TDPP)2 due to introduction of weak electron-donating phenylene bridge between two TDPPs. Consequently, the solar cell based on Ph(TDPP)2 achieved a PCE of 4.01% with high VOC of 0.93 V. |
