Strategies for optimizing the performance of carbazole thiophene appended unsymmetrical squaraine dyes for dye-sensitized solar cells.
Unsymmetrical squaraine dyes (CTSQ-1 and CTSQ-2) with carbazole thiophene donor units were synthesized, characterized and used as sensitizers in dye-sensitized solar cells (DSSCs). These squaraines exhibited intense absorption in the near IR-visible region of the solar spectrum both in solution and on TiO2 surface. The LUMO level of the parent sensitizer (CTSQ-2) was positioned at a potential much close to the conduction band of TiO2 resulting in lack of enough driving force for electron injection which was modulated by structurally changing the donor carbazole moiety (CTSQ-1), pushing the LUMO more positive thereby enhancing the driving force. Theoretical calculations were carried out in order to have a better understanding of the electron density distribution in CTSQ-1 and CTSQ-2. Electron injection dynamics in CTSQ-1 was studied in detail by changing the Li(+) concentration and its effects on photovoltaic parameters were discussed with the help of JV, IPCE, lifetime and EIS measurements.
Photosciences and Photonics Section, Chemical Sciences and Technology Division, CSIR-National Institute for Interdisciplinary Science and Technology, Trivandrum, 695 019, India. suraj@niist.res.in.
Suraj
S
Soman
M A
MA
Rahim
S
S
Lingamoorthy
Cherumuttathu H
CH
Suresh
Suresh
S
Das