The blending of organic semiconductor and insulating polymer as an active layer of organic transistors has been assessed by several studies and may open new possibilities for advantageous functions. However, studies on the use of insulating polymer doping in organic solar cells are rarely conducted. In this research, a blending film comprising regioregular poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) was doped with a soft insulating poly(methyl methacrylate) (PMMA) to act as an active layer of a solar cell. The fill factor (FF) and open-circuit voltage (V OC) of P3HT:PCBM solar cells were improved after PMMA doping. The microstructure-dependent photovoltaic properties of devices with different fractions of PMMA were investigated using spectroscopy and quantum chemical calculations. We highlight that PMMA doping leads to a more homogeneous conformation of P3HT chains, fewer vacancies, and fewer leakage pathways in blending films. Consequently, charges can be efficiently transported to the electrodes of devices, resulting in enhanced FF and V OC. The results of theoretical calculations at the microscopic molecular level also confirmed the enhanced electrical performance of devices from PMMA doping.

In this study, we fabricate ZnO thin films with nano-crystalline Si (nc-Si) quantum dots (QDs) using a ZnO/Si multilayer deposition structure and a post-annealing process, and the formation of high crystallinity of Si QDs embedded in the crystalline ZnO matrix is demonstrated. For optical properties, the essential features of ZnO material, high transmission in long-wavelength and high absorption in short-wavelength ranges, are preserved. We observe significantly enhanced light absorption and an unusual photoluminescence emission peak contributed from the nc-Si QDs in the middle-wavelength range. In addition, we confirm the formation of optical sub-bandgap and the obtained value is quite close to the unusual PL emission peak. We show that meaningful sub-bandgap can form in ZnO thin film by embedding nc-Si QDs while maintaining the advantageous properties of ZnO matrix. This newly developed composite material, nc-Si QD embedded ZnO thin films, can be useful for various electro-optical applications.

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In this study, synthesis and properties of green flame retardant of silane-functionalized expandable graphite (EG) composites were investigated. The coupling agent was used to improve the interface between the matrix and EG. Fourier transform infrared spectrophotometry and X-ray photoelectron spectroscopy were adopted to characterize the functionalized EG. It was affirmed that 3-aminopropyltriethoxsilane (APTS) has been grafted on EG. The modified EG composites improved thermal property, corresponding to functionalized EG. 29Si-nuclear magnetic resonance and scanning electron microscopies were used to study the structure and the morphology property of the modified EG composites. It showed that flake graphite existed in the matrix. Energy dispersive X-ray analysis indicated that Si atoms appeared due to APTS grafted on EG. The expanded structures of graphite were formed after burning. The foamed layer demonstrated the mechanism of protection of EG. The results present poly(methylmethacrylate)/silane-modified EG(PMMA, poly(methylmethacrylate) composites that have excellent thermal stability and flame-retardant property compared to pure PMMA resin.

A Si quantum dot (QD)-embedded ZnO thin film is successfully fabricated on a p-type Si substrate using a ZnO/Si multilayer structure. Its optical transmittance is largely improved when increasing the annealing temperature, owing to the phase transformation from amorphous to nanocrystalline Si QDs embedded in the ZnO matrix. The sample annealed at 700°C exhibits not only high optical transmittance in the long-wavelength range but also better electrical properties including low resistivity, small turn-on voltage, and high rectification ratio. By using ZnO as the QDs’ matrix, the carrier transport is dominated by the multistep tunneling mechanism, the same as in a n-ZnO/p-Si heterojunction diode, which clearly differs from that using the traditional matrix materials. Hence, the carriers transport mainly in the ZnO matrix, not through the Si QDs. The unusual transport mechanism using ZnO as matrix promises the great potential for optoelectronic devices integrating Si QDs.