Yu, J.J.YuShen, T.-L.T.-L.ShenWeng, W.-H.W.-H.WengHuang, Y.-C.Y.-C.HuangHuang, C.-I.C.-I.HuangSu, W.-F.W.-F.SuRwei, S.-P.S.-P.RweiHo, K.-C.K.-C.HoWEI-FANG SUKUO-CHUAN HOCHING-I HUANG2020-06-232020-06-23201216146832https://scholars.lib.ntu.edu.tw/handle/123456789/504239The heterojunction of poly(3-hexylthiophene) (P3HT) and TiO 2 in hybrid solar cells is systematically engineered with four cyanoacrylic acid-containing conjugated molecules with various lowest unoccupied molecular orbital (LUMO) levels, WL-1 to WL-4, which are prepared by the formylation of thiophene derivatives in a Vilsmeier-Haack reaction, followed by treatment with cyanoacetic acid. The optical characteristics, redox properties, and intrinsic dipole moments of these interfacial modifiers (IMs) are examined using UV-vis spectrophotometry, cyclic voltammetry, and density functional theory calculations. Using cyanoacrylic acid as a terminal anchoring group in IMs increases the electron affinity in regions close to the titania surface and forms a molecular dipole that is orientated away from the TiO 2 surface, enabling both open-circuit voltage (V OC) and short-circuit current density to be increased simultaneously. Photovoltaic measurements demonstrate that V OC increases with the dipole moment of IMs along the molecular backbone. Moreover, the external quantum efficiency (EQE) spectra display a bimodal distribution, revealing that both IMs and P3HT contribute to the photocurrent. The EQE at 570 nm is identified as characteristic of P3HT. More importantly, the LUMO of the IMs decisively determines the dissociation efficiency of P3HT excitons. The device based on P3HT/WL-4/TiO 2 exhibits the highest power conversion efficiency of 2.87%. © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.[SDGs]SDG7Anchoring groups; Bimodal distribution; Conjugated molecules; Cyanoacetic acids; Density functional theory calculations; Dissociation efficiency; External quantum efficiency; Formylation; Hybrid solar cells; Interfacial modifiers; Intrinsic dipole moment; Lowest unoccupied molecular orbital; Molecular design; Molecular dipole; Optical characteristics; Photovoltaic measurements; Poly-3-hexylthiophene; Power conversion efficiencies; Redox property; Thiophene derivatives; TiO; Titania surfaces; UV-vis spectrophotometry; Vilsmeier-Haack reaction; Conversion efficiency; Cyclic voltammetry; Density functional theory; Heterojunctions; Open circuit voltage; Quantum chemistry; Thiophene; Titanium dioxide; Solar cellsjournal article10.1002/aenm.201100581