Conduction band shift and interfacial charge transfer transition by adsorbed 4-teriary butyl pyridine analogues on TiO2: A density functional theory study

Additives are regular components in dye sensitized solar cell (DSSC) electrolyte preparations. 4-teriary butyl pyridine (4-TBP) is one of the most common additives in DSSC electrolytes. The role of 4-TBP at enhancing the open circuit voltage via negative shift of the conduction band edge of TiO2 is widely recognised, however, its capability for interfacial charge transfer transition (ICTT) is unknown. In this contribution we use DFT to examine adsorption of 4-TBP and its analogues on TiO2. The results show that 4-TBP is capable of ICTT in the UV region. Analogues bearing electron donating groups display ICTT in the visible region. While analogues bearing electron withdrawing groups may display no ICTT and cationic analogue displayed reversed ICTT. The results provide insights on the effect substituents on the negative shift of the conduction band edge of TiO2. The results also revealed wider scope for selection of additives for enhancing the performance of DSSCs.