Molecular Structure Effect of Pyridine-Based Surface Ligand on the Performance of P3HT:TiO₂ Hybrid Solar Cell

Abstract

Colloid TiO(2) nanorods are used for solution-processable poly(3-hexyl thiophene): TiO(2) hybrid solar cell. The nanorods were covered by insulating ligand of oleic acid (OA) after sol-gel synthesis. Three more conducting pyridine type ligands: pyridine, 2,6-lutidine (Lut) and 4-tert-butylpyridine (tBP) were investigated respectively to replace OA. The power conversion efficiency (PCE) of the solar cell was increased because the electronic mobility of pyridine-type ligand-modified TiO(2) is higher than that of TiO(2)-OA. The enhancement of PCE is in the descending order of Lut > pyridine > tBP because of the effective replacement of OA by Lut. The PCE of solar cell can be further enhanced by ligand exchange of pyridine type ligand with conjugating molecule of 2-cyano-3-(5-(7-(thiophen-2-yl)-benzothiadiazol-4-yl) thiophen-2-yl) acrylic acid (W4) on TiO(2) nanorods because W4 has aligned bandgap with P3HT and TiO(2) to facilitate charge separation and transport. The electronic mobility of two-stage ligand exchanged TiO(2) is improved furthermore except Lut, because it adheres well and difficult to be replaced by W4. The amount of W4 on TiO(2)-tBP is 3 times more than that of TiO(2)-Lut (0.20 mol % vs. 0.06 mol %). Thus, the increased extent of PCE of solar cell is in the decreasing order of tBP > pyridine > Lut. The TiO(2)-tBP-W4 device has the best performance with 1.4 and 2.6 times more than TiO(2)-pyridine-W4 and TiO(2)-Lut-W4 devices, respectively. The pKa of the pyridine derivatives plays the major role to determine the ease of ligand exchange on TiO(2) which is the key factor mandating the PCE of P3HT:TiO(2) hybrid solar cell. The results of this study provide new insights of the significance of acid-base reaction on the TiO(2) surface for TiO(2)-based solar cells. The obtained knowledge can be extended to other hybrid solar cell systems.

Copolymerization of EDOT with Pyrrole on TiO2 Semiconductor Films by One-Step Reaction, Structure-Dependent Electronic Properties, and Charge Conduction Models of the Composite Films

“…22 Recently, an improved poly(3-hexylthiophene)-TiO 2 heterojunction was achieved by anchoring a conjugated molecule of 2-cyano-3-(5-(7-(thiophen-2-yl)-benzothiadiazol-4-yl)thiophen-2-yl) acrylic acid on the colloid TiO 2 nanorods. 23 Also, to obtain an intimate poly(3-hexylthiophene)-TiO 2 heterojunction, a biomimetic initiator was grafted onto the TiO 2 surface to induce the ring-opening metathesis polymerization of 5-norbornene-2-methanol-3-thiopheneacetic acid ester monomers, followed by the oxidation polymerization of 3-hexylthiophene propagating at the thiophene derivative chain. 24 In the above strategies, a stepwise synthesis was usually employed to form the new heterojunctions.…”

Quasi-solid electrolyte with polyamidoamine dendron modified-talc applied to dye-sensitized solar cells

“…The phenomenon was also observed in a study of the addition of 4-tert-butylpyridine [47,49] or guanidinium [48] in liquid electrolytes and addition of montmorillonite in a gel electrolyte [4]. Additionally, the primary amine (pKa ¼ 7e9) [50] at the surface of the PAMAM dendron are strongest basic groups than the tert-butylpyridine molecule (pka ¼ 6) [51]. When the interlayer space of the organotalc increases, the organic groups of the dendron are more exposed to interact with TiO 2 surface.…”

Towards efficient and cost-effective inverted hybrid organic solar cells using inorganic semiconductor in the active layer

“…From Table 1, R s decreased from 9.1 to 7.7 X-cm 2 with increasing amounts of both nanoparticles. This decrease in R s value is referred to decrease in material resistivity with the addition of metal oxide as the addition leads to additional crosslink in the network of the active layer (Lin et al 2013). In contrast, a significant increase in R sh from 1120 to 2490 Xcm 2 because of suppression of leakage current caused by p and n-type NPs network (Saunders and Turner 2008;Huang et al 2009).…”