Hideo Ohkita

We report herein a comparison of the photophysics of a series of polythiophenes with ionization potentials ranging from 4.8 to 5.6 eV as pristine films and when blended with 5 wt % 1-(3-methoxycarbonyl)propyl-1-phenyl-[6,6]C61 (PCBM). Three polymers are observed to give amorphous films, attributed to a nonplanar geometry of their backbone while the other five polymers, including poly(3-hexylthiophene), give more crystalline films. Optical excitation of the pristine films of the amorphous polymer

Abstract Selective dye loading at the polymer/fullerene interface was studied for ternary blend bulk heterojunction solar cells, consisting of regioregular poly(3‐hexylthiophene) (RR‐P3HT), a fullerene derivative (PCBM), and a silicon phthalocyanine derivative (SiPc) as a light‐harvesting dye. The photocurrent density and power conversion efficiency of the ternary blend solar cells were most improved by loading SiPc with a content of 4.8 wt%. The absorption and surface energy measurements sugges

Polymer-based solar cells have made great progress during the past decade and consequently are now attracting extensive academic and commercial interest because of their potential advantages: lightweight, flexible, low cost, and high-throughput production. On the other hand, the recent progress in analytical tools has profoundly enhanced our understanding of the underlying mechanism of polymer-based solar cells, which can provide valuable guidelines for materials design and device engineering an

Multi-colored dye-sensitized polymer/fullerene solar cells with two different near-IR dyes, silicon phthalocyanine bis(trihexylsilyl oxide) (SiPc) and silicon naphthalocyanine bis(trihexylsilyl oxide) (SiNc), enhanced power conversion efficiency up to 4.3%, compared to that of the individual ternary blend solar cells with a single dye under AM1.5G illumination.

Initial improvement in power conversion efficiency (PCE) during ambient storage is often seen in perovskite solar cells (PSCs). In this work, we studied the origin of PCE enhancement by ambient storage on typical n-i-p PSCs. We found improvements in both fill factor and open-circuit voltage during the first 2 days of storage. By analyzing temperature and light intensity-dependent VOC, we found that the charge recombination mechanism changed from surface- to bulk-dominated because of defect passi

Ternary-blend polymer solar cells can be effectively improved by incorporating a heterostructured near-IR dye, which has a hexyl group compatible with the polymer and a benzyl group compatible with the fullerene. Because of the compatibility with both materials, the heterostructured dye can be loaded up to 15 wt% and hence can boost the photocurrent generation by 30%.

The photophysical properties of carbazole excimers were investigated using syn- and anti-[3.3](3,9)carbazolophanes: the syn-carbazolophane is a model compound for a fully overlapped carbazole excimer and the anti-carbazolophane for a partially overlapped carbazole excimer the structures of which have been determined by X-ray analysis. 1H NMR spectra showed that two carbazole moieties in the syn- and anti-[3.3](3,9)carbazolophanes did not flip even in solution owing to short [3.3](3,9)linkage: ge

Efficient triplet formation is observed for films of high ionisation potential polythiophenes blended with a fullerene derivative, and assigned to formation via geminate charge recombination of bound radical ion pair states.

In this review, we summarize recent progress in the development of π-conjugated polymers and molecules for organic photovoltaics that enable small photon energy loss and high power conversion efficiency at the same time.

The behavior of a photoejected electron with the parent cation formed through two-photon ionization of a dopant chromophore in poly(alkyl methacrylate)s and polystyrene was studied by measurement of the emission spectra of the charge recombination luminescence, i.e., isothermal luminescence (ITL) at 20 K and thermoluminescence (TL) at temperatures from 20 to 300 K. The ITL spectral shape remained the same between 10 min and 10 h after the photoirradiation. On the other hand, the intensity ratio

Time-resolved spectroscopy is a powerful tool for studying fundamental photophysics in optoelectronic materials on a molecular temporal scale. In this review, we describe transient spectroscopic studies on fundamental photovoltaic conversion processes in polymer solar cells, which consist of a series of conversion processes such as photon absorption, exciton diffusion into a donor/acceptor interface, charge transfer at the interface, charge dissociation into free charge carriers, and charge coll