A series of quinoxaline-based sensitizers were designed through the elongation of π-conjugation length based on the sense of directional electron transport from donor to acceptor. To facilitate an efficient intramolecular charge transfer, we introduced additional donor moieties and thiophene unit as light-absorbing chromophore and π-bridge. The photophysical and electrochemical properties of the synthesized dyes were investigated, and photovoltaic performances of the solar cells based on the sensitizers were also explored. Under AM 1.5 G simulated solar illumination, the dye with a pair of dimeric phenothiazine donors gave the best overall power conversion efficiency of 5.41% owing to its intense and broad visible light absorption. The insertion of a thiophene bridge between the phenothiazine and the quinoxaline ring improved the photovoltaic efficiency by impeding charge recombination and increasing electron lifetime. Optimization of the photovoltaic performance condition gave an overall efficiency of 6.48% for NQX8. The results led us to conclude that proper π-conjugation length, location of π-spacer, and molecular conformation should be considered when designing novel sensitizer structures for dye-sensitized solar cells (DSSCs).
Bibliographical noteFunding Information:
This work was supported by the Technology Innovation Program and the New and Renewable Energy Core Technology Program of the Korea Institute of Energy Technology Evaluation and Planning (KETEP) , and the granted financial resources from the Ministry of Trade, Industry and Energy, Republic of Korea (No. 10047756 and No. 20163030013960 ) The authors would also like to thank Prof. Sung Hoon Jeong (Smart Organic Materials Laboratory, Hanyang University, Korea) and Prof. Min Jae Ko (Advanced Energy Materials Laboratory, Hanyang University, Korea) for allowing us to use their equipment related to cell fabrication, solar simulators, EQE measurements, and EIS measurements.
All Science Journal Classification (ASJC) codes
- Chemical Engineering(all)
- Process Chemistry and Technology