Guanwen Yang

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Following the development of the bulk heterojunction1 structure, recent years have seen a dramatic improvement in the efficiency of polymer solar cells. Maximizing the open-circuit voltage in a low-bandgap polymer is one of the critical factors towards enabling high-efficiency solar cells. Study of the relation between open-circuit voltage and the energy(More)
Since the discovery of efficient electron transfer between fullerenes and conjugated polymers in bulk-heterojunction (BHJ) polymer solar cells, a lot of attention has been focused on engineering the properties of these systems. Especially, over the last five years, major improvements have been achieved in the performance of polymer solar cells. The(More)
Amethodwhichenables the investigationof theburied interfaceswithoutaltering the properties of the polymer films is used to study vertical phase separation of spin-coated poly(3-hexylthiophene) (P3HT):fullerene derivative blends. X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM) analysis reveals the P3HT enrichment at the free (air)(More)
Polymer-inorganic nanocrystal composites offer an attractive means to combine the merits of organic and inorganic materials into novel electronic and photonic systems. However, many applications of these composites are limited by the solubility and distribution of the nanocrystals in the polymer matrices. Here we show that blending CdTe nanoparticles into a(More)
Hsiang-Yu Chen,† Hoichang Yang,‡ Guanwen Yang,† Srinivas Sista,† Ruben Zadoyan,§ Gang Li, and Yang Yang*,† Department of Materials Science and Engineering, UniVersity of CaliforniasLos Angeles, Los Angeles, California 90095, Department of AdVanced Fiber Engineering, Inha UniVersity, Yonghyun-dong 253, Incheon 402-751, Korea, Technology and Applications(More)
Various mechanisms have been proposed to interpret switching effect in thermally evaporated organic memory devices. In this work, we demonstrate a nonvolatile memory device having tristates, one OFF state and two different ON states lower-ON state, higher-ON state in the metal-insulator-metal MIM structure. Detailed study has revealed that different(More)
The mechanical properties of glassy films and glass surfaces have been studied using an atomic force microscope (AFM) through various imaging modes and measuring methods. In this paper, we discuss the viscoelastic response of a glassy surface probed using an AFM. We analyzed the force-distance curves measured on a glassy film or a glassy surface at(More)
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