Synthesis and characterization of free base and metal porphyrins and their interaction with CdTe QDs

• The binding interaction of QDs with porphyrins having different number of methoxy groups and their electron transfer feasibilities was studied.
• The insertion of metal increases the binding affinity with QDs as compared to free base porphyrins.
• Porphyrin anion radical was observed in transient absorption measurements which reveal the electron transfer from QDs to porphyrin.
• The overall results will provide prolific information for the future modification of quantum dot solar cells.

Free base porphyrins and metalloporphyrins with different number of methoxy groups were synthesized to investigate the consequence of methoxy groups in the porphyrins on interaction with quantum dots through steady state, time resolved and transient absorption measurements. Spectral changes in the absorption and photoluminescence of quantum dots in the presence of porphyrins elucidate the binding affinity between them. From the photoluminescence quenching analysis, higher number of methoxy substituted zinc porphyrin was found to possess better binding affinity with quantum dots than the other porphyrins which divulges the role of methoxy substituents. The calculated reduction potential of the synthesized porphyrins was feasible for accepting electrons from the photoexcited quantum dots. Electron transfer mechanism is suggested based on energy level diagram, Rehm–Weller equation and transient absorption measurements.

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