Output current enhancement of hexylthiophene functionalized D–π-extended–A triphenylamine in dye sensitized solar cells

Abstract

In this work, we report the synthesis of triphenylamine based D–π-extended–A hexylthiophene functionalized MY-102 dye and its solar power conversion efficiency improvement in dye sensitized solar cells (DSCs). This dye was synthesized by Wittig, Suzuki and Sonogashira coupling reactions. The synthesized dye shows higher absorption wavelength and molar extinction coefficient (480 nm and 42 375 M⁻¹ cm⁻¹) compared to those of the reference TA-St-CA dye (469 nm and 21 803 M⁻¹ cm⁻¹). DFT and TD-DFT calculations of MY-102 dye show that the LUMO level of the dye lies closer to the conduction band (CB) edge of TiO₂. A power conversion efficiency of 5.07% is achieved by fabricating the solar cell with the conventional I₃⁻/I⁻ electrolyte compared to 4.26% obtained with the reference TA-St-CA dye. MY-102 dye fabricated with the Co(phen)₃²⁺ electrolyte shows an improvement in power conversion efficiency due to the increased V_OC. The I₃⁻/I⁻ electrolyte with a redox potential of 0.35 V is located at a much higher energy region compared to the HOMO level of MY-102 and near the conduction band edge of TiO₂. This limits both electron transfer to MY-102 and electron acceptance from TiO₂, affecting the V_OC and results in poor conversion efficiency. On the other hand, the Co(phen)₃²⁺ electrolyte with a redox potential of 0.62 V is located near the HOMO level of MY-102 and below the conduction band edge of TiO₂, which facilitates the efficient electron transfer and acceptance. This contributes to the V_OC of MY-102 dye and results in an outstanding conversion efficiency of 6.62%.