| 1. |
- Hou, Lintao, et al.
(författare)
-
Lateral Phase Separation Gradients in Spin-Coated Thin Films of High-Performance Polymer: Fullerene Photovoltaic Blends
- 2011
-
Ingår i: Advanced Functional Materials. - : Wiley. - 1616-3028 .- 1616-301X. ; 21:16, s. 3169-3175
-
Tidskriftsartikel (refereegranskat)abstract
- In this study, it is demonstrated that a finer nanostructure produced under a rapid rate of solvent removal significantly improves charge separation in a high-performance polymer: fullerene bulk-heterojunction blend. During spin-coating, variations in solvent evaporation rate give rise to lateral phase separation gradients with the degree of coarseness decreasing away from the center of rotation. As a result, across spin-coated thin films the photocurrent at the first interference maximum varies as much as 25%, which is much larger than any optical effect. This is investigated by combining information on the surface morphology of the active layer imaged by atomic force microscopy, the 3D nanostructure imaged by electron tomography, film formation during the spin coating process imaged by optical interference and photocurrent generation distribution in devices imaged by a scanning light pulse technique. The observation that the nanostructure of organic photovoltaic blends can strongly vary across spin-coated thin films will aid the design of solvent mixtures suitable for high molecular-weight polymers and of coating techniques amenable to large area processing.
|
|
| 2. |
- Wang, Ergang, 1981, et al.
(författare)
-
Side-Chain Architectures of 2,7-Carbazole and Quinoxaline-Based Polymers for Efficient Polymer Solar Cells
- 2011
-
Ingår i: Macromolecules. - : American Chemical Society (ACS). - 1520-5835 .- 0024-9297. ; 44:7, s. 2067-2073
-
Tidskriftsartikel (refereegranskat)abstract
- Three polymers bearing a common carbazole thiophene quinoxaline thiophene backbone, but different side chains, were designed and synthesized in order to investigate the effect of side chains on their photovoltaic performance. Their photophysical, electrochemical, and photovoltaic properties were investigated and compared. The polymer EWC3, with the largest amount of side chains, showed the highest power conversion efficiency of 3.7% with an open-circuit voltage (V-oc) of 0.92 V. The atomic force microscopy images of the active layers of the devices showed that the morphology was highly influenced by the choice of the solvent and processing additive. It is worth noting that polymer solar cells (PSCs) fabricated from EWC3, with branched side chains on the carbazole units, gave a much higher V-oc than the devices made from EWC1, which bears the same electron-deficient segment as EWC3 but straight side chains on carbazole units. This study offered a useful and important guideline for designing 2,7-carbazole-based polymers for high-performance PSCs.
|
|
| 3. |
- Wang, Zhongqiang, et al.
(författare)
-
Mixed solvents for reproducible photovoltaic bulk heterojunctions
- 2011
-
Ingår i: Journal of Photonics for Energy. - : SPIE-Intl Soc Optical Eng. - 1947-7988. ; 1:1 (Special Section on Organic Photovoltaics), s. 011122-
-
Tidskriftsartikel (refereegranskat)abstract
- Most efficient polymer solar cells are usually fabricated from toxic organic solvents, such as chloroform, chlorobenzene, or dichlorobenzene (ODCB). Here, we demonstrate a power conversion efficiency of 4.5% in solar cells with a new blue polymer poly[2,3-bis-(3-octyloxyphenyl)quinoxaline-5,8-diyl-alt-thiophene-2,5-diyl] (TQ1) mixed with PC71BM and processed from mixed solvents of toluene and ODCB in a ratio of 9:1. Decreasing the content of ODCB makes device processing more compatible with the environment for large scale production, with 10% reduction of photocurrent compared to devices from pure ODCB under optimized conditions. In addition, less variation of photocurrent is obtained in solar cells processed from mixed solvents than from pure ODCB due to varying nanostructure in the blends, which is also critical for production.
|
|
