Discrepancy of Optimum Ratio in Bulk Heterojunction Photovoltaic Devices: Initial Cell Efficiency vs Long-Term Stability

Organic photovoltaic devices are difficult to commercialize because of their vulnerability to chemical degradation related with oxygen and water and to physical degradation with aging at high temperatures. We investigated the photophysical degradation behaviors of a series of poly­(3-hexylthiophene) (P3HT)/[6,6]-phenyl C61-butyric acid methyl ester (PC₆₀BM) bulk heterojunctions (BHJs) as a model system according to the donor–acceptor ratio. We found that the optimum P3HT:PC₆₀BM ratio in terms of long-term stability differs from that in terms of initial cell efficiency. On the basis of cell performance decays and time-resolved photoluminescence measurements, we investigated the effects of oxygen and material self-aggregation on the stability of an organic photovoltaic device. We also observed the changes in morphological geometry and analyzed the surface elements to verify the mechanisms of degradation

Direct Low-Temperature Growth of Single-Crystalline Anatase TiO₂ Nanorod Arrays on Transparent Conducting Oxide Substrates for Use in PbS Quantum-Dot Solar Cells

We report on the direct growth of anatase TiO₂ nanorod arrays (A-NRs) on transparent conducting oxide (TCO) substrates that can be directly applied to various photovoltaic devices via a seed layer mediated epitaxial growth using a facile low-temperature hydrothermal method. We found that the crystallinity of the seed layer and the addition of an amine functional group play crucial roles in the A-NR growth process. The A-NRs exhibit a pure anatase phase with a high crystallinity and preferred growth orientation in the [001] direction. Importantly, for depleted heterojunction solar cells (TiO₂/PbS), the A-NRs improve both electron transport and injection properties, thereby largely increasing the short-circuit current density and doubling their efficiency compared to TiO₂ nanoparticle-based solar cells

Iridium Complexes Containing Bis(imidazoline thione) and Bis(imidazoline selone) Ligands for Visible-Light-Induced Oxidative Coupling of Benzylamines to Imines

Novel iridium­(III) complexes containing bis­(N-heterocyclic carbene), bis­(imidazoline thione) <b>L2</b>, and bis­(imidazoline selone) <b>L3</b> were prepared. The iridium complexes bearing <b>L2</b> and <b>L3</b> showed the significant absorption of visible light with maximum intensity at ∼460 nm. Bis­(2-(2′-benzothienyl)­pyridinato)­iridium­(III) complexes (<b>Ir-6</b>) with <b>L3</b> showed excellent ability as a photosensitizer of visible light. Under blue LED irradiation with maximum emission at 460 nm, 0.25 mol % <b>Ir-6</b> showed 94% conversion of benzylamine for 5 h at room temperature. Through mechanistic studies, it was suggested that the photoinduced oxidative coupling of benzylamine by <b>Ir-6</b> follows a singlet oxygen pathway. The excellent performance of <b>Ir-6</b> originated from the efficient visible light absorption at 460 nm and the enhanced triplet state due to the heavy-atom effect of <b>L3</b>. This work shows that bis­(imidazoline thione) and bis­(imidazoline selone) can be efficient ligands for tuning the optical properties of iridium­(III) complexes

Hollow Microporous Organic Networks Bearing Triphenylamines and Anthraquinones: Diffusion Pathway Effect in Visible Light-Driven Oxidative Coupling of Benzylamines

Hollow microporous organic networks were prepared by using silica spheres as the template and tris­(4-ethynylphenyl)­amine and 2,6-diiodo-9,10-anthraquinone as the building blocks for the Sonogashira coupling. The resultant materials bearing triphenylamine and anthraquinone moieties showed efficient visible light absorption and catalytic activities in the photochemical oxidative coupling of benzylamines. Through the comparison studies of hollow and nonhollow catalytic materials, the diffusion pathway effect of the substrates was clearly observed in the photochemical conversion of benzylamines