We report an enhancement in the efficiency of organic solar cells via the incorporation of gold (Au) or silver (Ag) nanoparticles (NPs) in the hole-transporting buffer layer of poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS), which was formed on an indium tin oxide (ITO) surface by the spin-coating of PEDOT:PSS-Au or Ag NPs composite solution. The composite solution was synthesized by a simple in situ preparation method which involved the reduction of chloroauric acid (HAuCl4) or silver nitrate (AgNO3) with sodium borohydride (NaBH4) solution in the presence of aqueous PEDOT:PSS media. The NPs were well dispersed in the PEDOT:PSS media and showed a characteristic absorption peak due to the surface plasmon resonance effect. Organic solar cells with the structure of ITO/PEDOT:PSS-Au, Ag NPs/poly(3-hexylthiophene):[6,6]-phenyl-C61-butyric acid methyl ester (P3HT:PCBM)/LiF/Al exhibited an 8% improvement in their power conversion efficiency mainly due to the enlarged surface roughness of the PEDOT:PSS, which lead to an improvement in the charge collection and ultimately improvements in the short-circuit current density and fill factor.

The use of porous three-dimensional (3D) composite scaffolds has attracted great attention in bone tissue engineering applications because they closely simulate the major features of the natural extracellular matrix (ECM) of bone. This study aimed to prepare biomimetic composite scaffolds via a simple 3D printing of gelatin/hyaluronic acid (HA)/hydroxyapatite (HAp) and subsequent biomineralization for improved bone tissue regeneration. The resulting scaffolds exhibited uniform structure and homogeneous pore distribution. In addition, the microstructures of the composite scaffolds showed an ECM-mimetic structure with a wrinkled internal surface and a porous hierarchical architecture. The results of bioactivity assays proved that the morphological characteristics and biomineralization of the composite scaffolds influenced cell proliferation and osteogenic differentiation. In particular, the biomineralized gelatin/HA/HAp composite scaffolds with double-layer staggered orthogonal (GEHA20-ZZS) and double-layer alternative structure (GEHA20-45S) showed higher bioactivity than other scaffolds. According to these results, biomineralization has a great influence on the biological activity of cells. Hence, the biomineralized composite scaffolds can be used as new bone scaffolds in bone regeneration.

To provide adequate conditions for the regeneration of damaged bone, it is necessary to develop piezoelectric porous membranes with antioxidant and anti-inflammatory activities. In this study, composite nanofibers comprising poly(vinylidene fluoride) (PVDF) and a polyhedral oligomeric silsesquioxane–epigallocatechin gallate (POSS–EGCG) conjugate were fabricated by electrospinning methods. The resulting composite nanofibers showed three-dimensionally interconnected porous structures. Their average diameters, ranging from 936 ± 223 nm to 1094 ± 394 nm, were hardly affected by the addition of the POSS–EGCG conjugate. On the other hand, the piezoelectric β-phase increased significantly from 77.4% to 88.1% after adding the POSS–EGCG conjugate. The mechanical strength of the composite nanofibers was ameliorated by the addition of the POSS–EGCG conjugate. The results of in vitro bioactivity tests exhibited that the proliferation and differentiation of osteoblasts (MC3T3-E1) on the nanofibers increased with the content of POSS–EGCG conjugate because of the improved piezoelectricity and antioxidant and anti-inflammatory properties of the nanofibers. All results could suggest that the PVDF composite nanofibers were effective for guided bone regeneration.

At an elevated temperature of 90 °C, a chemical bath deposition using an aqueous solution of Zn(NO₃)₂·6H₂O and (CH₂)₆N₄ resulted in the formation of both nanoflowers and microrods of ZnO on F-doped SnO₂ glass with a seed layer. The nanoflowers and microrods were sensitized with dyes for application to the photoelectrodes of dye-sensitized solar cells (DSSCs). By extending the growth time of ZnO, the formation of nanoflowers was reduced and the formation of microrods favored. As the growth time was increased from 4 to 6 and then to 8 h, the open circuit voltage (V_oc) values of the DSSCs were increased, whilst the short circuit current (J_sc) values varied only slightly. Changes in the dye-loading amount, dark current, and electrochemical impedance were monitored and they revealed that the increase in V_oc was found to be due to a retardation of the charge recombination between photoinjected electrons and I₃⁻ ions and resulted from a reduction in the surface area of ZnO microrods. A reduced surface area decreased the dye contents adsorbed on the ZnO microrods, and thereby decreased the light harvesting efficiency (LHE). An increase in the electron collection efficiency attributed to the suppressed charge recombination counteracted the decreased LHE, resulting in comparable J_sc values regardless of the growth time.

By simple soaking titanium dioxide (TiO₂) films in an aqueous Na₂S solution, we could prepare surface-modified photoanodes for application to dye-sensitized solar cells (DSSCs). An improvement in both the open-circuit voltage (V_oc) and the fill factor (FF) was observed in the DSSC with the 5 min-soaked photoanode, compared with those of the control cell without any modification. The UV–visible absorbance spectra, UPS valence band spectra, and dark current measurements revealed that the Na₂S modification led to the formation of anions on the TiO₂ surface, and thereby shifted the conduction band edge of TiO₂ in the negative (upward) direction, inducing an increase of 29 mV in the V_oc. It was also found that the increased FF value in the surface-treated device was attributed to an elevation in the shunt resistance.

ZnO nanorods were formed by chemical bath deposition on fluorine–doped tin oxide (FTO) glass and the photovoltaic performance of ZnO-based dye-sensitized solar cells (DSCs) was investigated. A DSC with 8 h-grown ZnO nanorods showed a higher power conversion efficiency (PCE) than devices with 4, 6, and 10 h-grown ones. Further improvement in PCE was achieved in a cell with a silver-ion-deposited ZnO/FTO electrode. By deposition of Ag⁺ on the surface of the 8 h-grown ZnO nanorods, the dye-loading amount increased by approximately 210%, compared to that of pristine ZnO nanorods, resulting in a 1.8-times higher PCE. A DSC with the pristine ZnO/FTO electrode showed a PCE of 0.629%, while in a device with the silver-ion-deposited ZnO/FTO, the PCE increased to 1.138%. In addition, interfacial resistance at the ZnO/dye/electrolyte was reduced to approximately 170 Ω from 460 Ω for the control cell with the pristine ZnO/FTO. We attributed the higher dye-loading amount in the silver-ion-deposited ZnO/FTO to the electrostatic attraction between the positively charged ZnO and carboxylate anions (–COO⁻) of the N719 dyes.