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Interfacial engineering for highly efficient organic solar cells
Walker Bright James,최효성,김진영 한국물리학회 2017 Current Applied Physics Vol.17 No.3
Interfacial engineering using metal oxides, organic surface modifiers and other materials can effectively enhance the performance of conventional and inverted organic solar cells by reducing energy barriers for charge transport, while improving compatibility between organic active layer and inorganic metal oxides or transparent conducting electrodes. This short review introduces several important classes of interfacial materials which have been widely successful in improving the efficiency of organic solar cells, and covers some of the recent advances in this field.
Walker, Bright,Liu, Jianhua,Kim, Chunki,Welch, Gregory C.,Park, Jin Keun,Lin, Jason,Zalar, Peter,Proctor, Christopher M.,Seo, Jung Hwa,Bazan, Guillermo C.,Nguyen, Thuc-Quyen The Royal Society of Chemistry 2013 ENERGY AND ENVIRONMENTAL SCIENCE Vol.6 No.3
<P>We report a series of solution-processable, small-molecule, donor materials based on an architecture consisting of two diketopyrrolopyrrole (DPP) cores with different aromatic π-bridges between the DPP units and different end-capping groups. In general, this architecture leads to desirable light absorption and electronic levels for donor materials. Out of the compounds investigated, a material with a hydrolyzed dithieno(3,2-<I>b</I>;2′,3′-<I>d</I>)silole (SDT) core and 2-benzofuran (BFu) end capping groups leads to the most favorable properties for solar cells, capable of generating photocurrent up to 800 nm while producing an open-circuit voltage of over 850 mV, indicating a small loss in electrical potential compared to other bulk heterojunction systems. Device properties can be greatly improved through the use of solvent additives such as 2-chloronaphthalene and initial attempts to optimize device fabrication have resulted in power conversion efficiencies upwards of 4%.</P> <P>Graphic Abstract</P><P>A series of small-molecule donor materials based on an architecture consisting of two diketopyrrolopyrrole (DPP) moieties with different core and end groups is reported. <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=c3ee24351f'> </P>
Effect of Heterocyclic Anchoring Sequence on the Properties of Dithienogermole-Based Solar Cells
Walker, Bright,Han, Daehee,Moon, Mijin,Park, Song Yi,Kim, Ka-Hyun,Kim, Jin Young,Yang, Changduk American Chemical Society 2017 ACS APPLIED MATERIALS & INTERFACES Vol.9 No.8
<P>The synthesis and characterization of two new small molecular donor materials, DTGe(ThFBTTh2)(2) and DTGe(FBTTh3)(2), are presented for application in organic solar cells. These two materials represent structural evolutions of the high-efficiency, dithienogermole (DTGe)-cored small molecule DTGe(FBTTh2)(2), in which the conjugation length in the backbone was extended by incorporating additional thiophene units. Using the same molecular framework, we have evaluated how the anchoring sequence of heterocyclic units influences material properties and function in solar cell devices. It was found that incorporating additional thiophene units into the backbone, regardless of the position in the molecular platform, caused a small reduction in band gaps; however, both highest occupied molecular orbitals and lowest unoccupied molecular orbital energy bands were at lower energies when the thiophenes were incorporated near the terminus of the molecule. The film morphologies of both materials could be controlled by either thermal or solvent vapor annealing to yield phase separation on the order of tens of nanometers and improved crystallinity. Peak power-conversion efficiencies of 3.6% and 3.1% were obtained using DTGe(ThFBTTh2)(2) and DTGe(FBTTh3)(2), after solvent vapor treatment and thermal annealing, respectively. Our study provides a detailed analysis of how the ordering sequence of heterocyclic building blocks influences the properties and function of organic solar cells.</P>
Size tailoring of aqueous germanium nanoparticle dispersions.
Kim, Seongbeom,Walker, Bright,Park, Song Yi,Choi, Hyosung,Ko, Seo-Jin,Jeong, Jaeki,Yun, Myoung Hee,Lee, Jeong Chul,Kim, Dong Suk,Kim, Jin Young RSC Pub 2014 Nanoscale Vol.6 No.17
<P>We demonstrate a practical route to synthesize Ge nanoparticles (NPs) in multi-gram quantities via the laser pyrolysis of GeH4 gas. The size of the as-produced Ge NPs can be precisely controlled in the range of 19.0 to 65.9 nm via a subsequent etching procedure using a dilute H2O2 solution. Stable water dispersions of Ge NPs yield particles with a Ge/GeO2 core-shell structure, however, the oxide shell can easily be removed and passivated by treatment with HCl. The feed materials used in this process are readily available and lead to non-toxic, water-based dispersions of Ge NPs. The scalability and convenience of this procedure make it attractive as a method to obtain Ge NP dispersions for use in applications such as optoelectronic devices and biosensors.</P>