Correlating Interface Heterostructure, Charge Recombination, and Device Efficiency of Poly(3-hexyl thiophene)/TiO₂ Nanorod Solar Cell

The charge recombination rate in poly(3-hexyl thiophene)/TiO2 nanorod solar cells is demonstrated to correlate to the morphology of the bulk heterojunction (BHJ) and the interfacial properties between poly(3-hexyl thiophene) (P3HT) and TiO2. The recombination resistance is obtained in P3HT/TiO2 nanorod devices by impedance spectroscopy. Surface morphology and phase separation of the bulk heterojunction are characterized by atomic force microscopy (AFM). The surface charge of bulk heterojunction is investigated by Kelvin probe force microscopy (KPFM). Lower charge recombination rate and lifetime have been observed for the charge carriers in appropriate heterostructures of hybrid P3HT/TiO2 nanorod processed via high boiling point solvent and made of high molecular weight P3HT. Additionally, through surface modification on TiO2 nan,orod, decreased recombination rate and longer charge carrier lifetime are obtained owing to creation of a barrier between the donor phases (P3HT) and the acceptor phases (TiO2). The effect of the film morphology of hybrid and interfacial properties on charge carrier recombination finally leads to different outcome of photovoltaic I–V characteristics. The BHJ fabricated from dye-modified TiO2 blended with P3HT exhibits 2.6 times increase in power conversion efficiency due to the decrease of recombination rate by almost 2 orders of magnitude as compared with the BHJ made with unmodified TiO2. In addition, the interface heterostructure, charge lifetime, and device efficiency of P3HT/TiO2 nanorod solar cells are correlated

Surface roughness of CP-Ti, Ti6Al4V and sputtered Ti specimen after oxygen plasma treatment for different lengths of time, respectively.

<p>Star sign means significant difference (<i>p</i> < 0.05).</p

Normalized XPS spectra of (a) CP-Ti, (b) Ti6Al4V and (c) sputtered Ti before and after oxygen plasma treatment for different lengths of time.

<p>Normalized XPS spectra of (a) CP-Ti, (b) Ti6Al4V and (c) sputtered Ti before and after oxygen plasma treatment for different lengths of time.</p

Surface roughness of CP-Ti, Ti6Al4V and sputtered Ti specimen after oxygen plasma treatment for different lengths of time, respectively.

<p>Star sign means significant difference (<i>p</i> < 0.05).</p

Topographic images with section analysis of sputtered Ti substrates: (a) untreated, (b) OPT for 5 minutes, (c) OPT for 10 minutes and (d) OPT for 30 minutes.

<p>Topographic images with section analysis of sputtered Ti substrates: (a) untreated, (b) OPT for 5 minutes, (c) OPT for 10 minutes and (d) OPT for 30 minutes.</p

Water contact angles of CP-Ti and Ti6Al4V specimen treated by oxygen plasma.

<p>Water contact angles of CP-Ti and Ti6Al4V specimen treated by oxygen plasma.</p

The results of MTT assay of CP-Ti and Ti6Al4V.

<p>In CP-Ti groups, star sign means significant difference; as well as Ti6Al4V groups, different letter meant statistic different. (<i>p</i> < 0.05).</p

The F-actin immunofluorescence staining of MG-63 cell line cultured on CP-Ti and Ti6Al4V (200x).

<p>(a) is CP-Ti, and (b) is Ti6Al4V. The blue ovoid to round dots was the portion of cell nuclei. The cell shape of CP-Ti Control was polygonal, as well as spindle shape of other groups. All cells cultured on Ti6Al4V displayed spindle shape.</p

Reaction Kinetics and Formation Mechanism of TiO₂ Nanorods in Solution: An Insight into Oriented Attachment

The reaction kinetics and formation mechanism of oriented attachment for shaped nanoparticles in solution are not well-understood. We present the reaction kinetics and formation mechanism of organic-capped anatase TiO₂ nanorods in solution as a case study for the oriented attachment process using small-angle X-ray scattering (SAXS) and transmission electronic microscopy. The SAXS analysis qualitatively and quantitatively provides in-depth understanding of the mechanism, including the structural evolution, interparticle interaction, and spatial orientation of nanoparticles developed from nanodots to nanorods during the nucleation, isotropic, and anisotropic growth steps. The present study demonstrates the growth details of oriented attachment of nanoparticles in solution. An ordered lamellar structure in the solution is constructed by the balance of interaction forces among surface ligands, functional groups, and solvent molecules serving as a natural template. The template allows the alignment of spherical nanoparticles into ordered chain arrays and facilitates simultaneous transformation from spherical to rod shape via proximity attachment. The proposed model reveals an insight into the oriented attachment mechanism. This multistep formation mechanism of TiO₂ nanorods in solution can provide the fundamental understanding of how to tune the shape of nanoparticles and further control the aggregation of spatial nanorod networks in solution