K. T. Hung

Efficiency improvement of blended poly(3-hexylthiophene) and 1-(3-methoxycarbonyl)-propyl-1-phenyl-(6,6)C61 solar cells by nanoimprinting

This work demonstrates the effects of nanoimprinting on poly(3-hexylthiophene) and 1-(3-methoxycarbonyl)-propyl-1-phenyl-(6,6)C61 (P3HT:PCBM)-blended organic solar cells at room temperature. Textured Si wafer was used as a stamp. Nanoimprinting significantly increased the open-circuit voltage, the short-circuit current, and the fill factor, increasing the power conversion efficiency by ∼50%. The fill factor contributed most to the cell efficiency. Upon nanoimprinting, not only the surface structure but also the applied pressure contributed to the performance of the device. The origin of the hydrostatic pressure-induced efficiency improvement was also investigated. The proposed approach has potential to be applied in the future to improve the efficiency of various organic solar cells.

Low-Energy Ion-Beam-Assisted Sputtering for Si Nanocrystals

This work reports the low-energy ion-beam assisted sputtering (IBAS) for synthesis of the Si-rich oxide (SRO) films. The ion beams provided additional energy for the species to form crystallinic bonding and to crack the large radical in plasma. The IBAS effectively increased the density of Si NCs and lowered the required annealing temperature. Additionally, the IBAS showed capability to modulate the size and density of Si nanocrystals (NCs) in SRO films. Room-temperature photoluminescence for the unannealed SRO films that was prepared by the IBAS was observed. The annealing increased the PL intensity and the emission wavelength. The SRO films that were prepared by sputtering and IBAS were compared, and the corresponding material and optical properties were investigated. Finally, we suggest the proposed method will be useful for future development of Si NCs.

Sodium Doping at CuPc/C60 Interface for Photovoltaic Application

Alkali metal doped CuPc has been reported to have marked energy level shifts. The fundamental physics of the metal-organic interface have been extensively applied to improve OPVs and organic light-emitting devices. Most organic-organic donor-acceptor (D-A) interfaces have very small vacuum level offset, owing to their electronic wave functions are weakly coupled. Therefore, energy-level alignment at organic-organic interfaces has been studied less than that at metal-organic interfaces.