局部表面電漿，添加劑與不同溶劑對塊材異質界面高分子/富勒烯碳球太陽能電池主動層光吸收與形貌之影響

Polymer solar cells can be fabricated from a wide range of materials with different aesthetic and optoelectronic properties by a multiple set of processes. This results in a unique versatility in device form factor and functionality, which will enable performance optimization and commercialization. The relationship between process and morphology of device active layer is unique and multiple, therefore, controlling the active layer morphology with new conjugated polymer and fullerene derivatives has been a subject of attention for many researchers. The signature optical property of noble metal nanoparticles (NPs) is their localized surface plasmon resonance (LSPR). This phenomenon leads to enhanced light absorption and scattering cross sections for electromagnetic waves, as well as a strongly enhanced of the power conversion efficiency (PCE) of polymer solar cells. The PCE of polymer/fullerene solar cells are critically dependent on the morphologies of their active layers, which are typically processed from solution. The structural transition from solutions to solid films of the crystalline polymer is one of the grand challenges in the field. Simultaneously, the morphology of the active layer can be influenced to some extent by varying such parameters as the chemical composition, the solvent used, and the postproduction treatment conditions, but often it is not understood a priori. The use of a solvent additive to control the morphology of the active layer is one of the simplest and most effective methods for optimizing the performance of a BHJ device. PCE can also be significantly affected by the orientation of face- and edge-on polymer lamellar crystals, relative to the substrate surface, as well as the sizes of the fractal-like PC71BM clusters in the active layer. In the first, we investigated the effects of plasmonic resonances induced by gold nanodots (Au NDs), thermally deposited on the active layer, and octahedral gold nanoparticles (Au NPs), incorporated within the hole transport layer, on the performance of bulk heterojunction polymer solar cells (PSCs) based on poly(3-hexyl thiophene) (P3HT) and [6,6]-phenyl-C61butyric acid methyl ester (PC61BM). Thermally deposited Au-NDs and embedding Au NPs within the poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) to form a dual metallic nanostructure can further enhance PCE to 4.8%—that is about 20% greater than that of the conventional P3HT:PC61BM cell. In the second, using synchrotron wide- and small-angle X-ray scattering, we have elucidated the intricate mechanism of the hierarchical structural transitions from solutions to solid films of the crystalline polymer poly[bis(dodecyl)thiophene- thieno[3,4-c]pyrrole-4,6-dione] (PBTTPD) and [6,6]-phenyl-C71-butyric acid methyl ester (PC71BM), including the effect of the solvent additive 1,6-diiodohexane (DIH). We found that the local assembly of rigid-rod PBTTPD segments (ordered nano-domains) that formed in solution instantly and then relaxed within several hundred seconds upon cooling to room temperature from 90℃ could develop into seeds for subsequent crystallization of the polymer in the solid films. Concurrently, the sizes of the PBTTPD network structures in the blend solutions decreased and became more compact, and the PC71BM-rich domains increased upon decreasing the temperature; in the presence of additive DIH, these variations in the structures in solutions that were subject to the same cooling were substantially mitigated. The polymer’s crystallinity and the fullerene packing were both enhanced in the subsequent solid films that were processed involving DIH when the solvent removal process was relatively rapid. Our results provide a detailed understanding of the mechanism behind the structural development of polymer/fullerene blends upon their transitions from solution to the solid state, as well as the key functions of the additive. In the third, we used (i) synchrotron grazing-incidence small-/wide-angle X-ray scattering to elucidate the crystallinity of the polymer PBTC12TPD and the sizes of the clusters of the fullerenes PC61BM and ThC61BM and (ii) transmission electron microscopy/electron energy loss spectroscopy to decipher both horizontal and vertical distributions of fullerenes in PBTC12TPD/fullerene films processed with chloroform, chlorobenzene and dichlorobezene. We found that the crystallinity of the polymer and the sizes along with the distributions of the fullerene clusters were critically dependent on the solubility of the polymer in the processing solvent when the solubility of fullerenes is much higher than that of the polymer in the solvent. Finally, we employed 1-chloronaphthalene (CN) and 1,8-diiodooctane (DIO) as binary additives exhibiting relatively complementary preferential solubility for the crystalline conjugated polymer poly[bis(dodecyl)thiophene-dodecyl-thieno[3,4-c] pyrrole-4,6-dione] (PBTC12TPD) and the fullerene [6,6]-phenyl-C71-butyric acid methyl ester (PC71BM) in chloroform, allowing us to tune the amount of edge-on and face-on polymer lamellae and size of PC71BM clusters in the active layer in bulk heterojunction (BHJ) solar cells. The power conversion efficiency of a device incorporating an active layer of PBTC12TPD/PC71BM (1:1.5, w/w) processed with 0.5% DIO and 1% CN as additives in chloroform increased to 6.8% from a value of 4.9%, a relative increase of 40%, for the corresponding device containing the same active layer but processed without any additive.