The field performance of 'Fuyu' and 'Hiratanenashi' Japanese persimmon (Diospyros kaki Thunb.) trees grafted onto rootstocks propagated from cuttings of root suckers of dwarfed trees (R-a and R-b) was investigated over seven years. The results were then compared with the performance of trees grafted onto seedling stocks (S) as well as that of micropropagated and own-rooted trees (O-R). Shoot growth of both cultivars on R-b was less vigorous than that on R-a, while tree height of 'Hiratanenashi' on R-a was the same as that of both S and O-R. Secondary shoots on R-b trees were scarce in both cultivars in the fifth and sixth years. On R-b, both cultivars bore flowers soon after field establishment and thereafter continued to do so abundantly, with the percentage of flower-bearing shoots on R-b trees being the highest for each study year. Yield efficiencies calculated by units of trunk cross-sectional area, canopy area, and canopy volume showed that R-b trees produced fruit most effectively, although the total yields during the three harvest years were not significantly different between rootstocks. The appearance of the graft union with R-b varied depending on the scion cultivar, but no union was damaged by the occurrence of several typhoons, which uprooted a number of trees. These results show the possibility of using R-b propagated by cutting as a dwarfing rootstock for persimmon trees. Overall, the R-b rootstock improved yield efficiency, although fruit quality requires further investigation because it is thought to be affected by rootstock type.

We demonstrate the magnetoconductance (MC) effect originated from depressing the spin mixing in encounter pairs under the external magnetic field provides quantitative information about the singlet fission, the charge recombination and the trap-related dynamics with triplet exciton in a bilayer device of pentacene (Pen) and fullerene (C 60 ). Three MC effects in low-, moderate-and high-fields were detected in the bilayer device at room temperature. Kinetic analysis of the low-field MC effect showed that the charge recombination yield at the Pen|C 60 interface is ~1 %. Quantum mechanical simulations of spin-carrying pairs following the conservation rule of spin angular momentum in recombination showed that the moderate-and high-field MC effects are caused by, respectively, the trap-related dynamics with triplet exciton and the singlet fission with a maximum yield of 52 % in the layers. The quantitative information obtained by investigating the MC effect will contribute to the development of high-efficiency OSC devices.

The magnetoconductance (MC) effect was investigated for two types of organic solar cells with single junction (SJ) and bulk junction (BJ) of poly(3-hexylthiophene) (P3HT) as donor (D) and [6,6]-phenyl-C 61 -butyric acid methyl ester (PCBM) as acceptor (A). Three components with different half-field-at-half-maximums ( B 1/2 ) of 4 ± 1, 20 ± 15 and >400 mT, hereafter referred to MC S,M,B in a sequence, were observed in the magnetic field dependence of the MC effects measured under dark and light conditions. The magnitude of the MC S,M,B components is sensitive to not only the junction structure of the cell but also the presence or absence of incident light. The bias voltage ( V ) dependence of the MC effect in the dark for the SJ-cell is maximized around the turn-on voltage ( V ON ) of the dark current, where a flat band condition of the active layer is achieved. The B 1/2 for the MC M component of the SJ-cell increases with V beyond V ON . In light, the BJ-cell exhibits the MC effect, whereas no effect is detected for the SJ-cell. The MC S,M components for the BJ-cell in light increase with the incident light power. The transient MC S,M components for the BJ-cell measured using a nanosecond pulse laser increases with the delay time after the flash. By integrating these phenomena and the phase of the MC effect, it is concluded that all of the MC components arise from the magnetic field effect on the spin conversion of nongeminate electron (e)–hole (h) pairs with spin-dependent charge recombinations at the D/A-interface. The B 1/2 values for MC S,M,B are, respectively, understood by the spin conversion due to the hyperfine interaction, the spin relaxation, and the g -factor difference for e (PCBM – ) and h (P3HT + ). Kinetic simulations of the MC S,M components for the BJ-cell observed at the short-circuit condition in light yield an efficiency of ca. 40% for the nongeminate recombination, which is accompanied by the generation of triplet excitons as well as relaxation to a ground singlet state. The loss mechanism of moderate triplet recombination suggests an important possibility to improve the power conversion efficiency by harvesting of the triplet excitons.