Abstract
Boron dipyrromethene (BODIPY) being a chromophoric dye molecule has been extensively studied in dye sensitized solar cell (DSSC), imaging, and dye laser application. BODIPY is a stable boron complex with a broad absorption and photoluminescence (PL) in the visible region of solar radiation. This class of molecules show anomalous photophysical properties, which varies with concentration of the molecule. Here, we report the thorough analysis of photophysical study after synthesized the BODIPY molecule, which made up of two thiophene BODIPY cores comprising a phenyl spacer in between, coded as TG2 dye molecule. Steady state and time resolved concentration dependent PL reveal that, at very low concentration (nM) TG2 shows both Si (first excited state) and S-2 (second excited state) PL. Importantly, at higher concentration (mM) TG2 found to exist in aggregated state. Optical absorption and PL studies confirmed that TG2 exists in mixture of J-/H- aggregate state. Moreover, femtosecond transient absorption (fs-TA) analysis has been studied following 400 nm optical pump, which reveals that the excited singlet state converted to the mixed aggregated state with in an average time constant of 6 ps.