Poly bulk heterojunction

Nowadays the best performing organic photovoltaic cell is represented by a bulk heterojunction (BHJ) solar cell based on the polymer poly(3-hexylthiophene) (P3HT) and the fullerene derivative [6, 6]-phenyl-C61-butyric acid methyl ester (PCBM), with reproducible efficiencies approaching 5% [262,263], However, a serious drawback for the preparation of efficient organic photovoltaic cells is represented by the low optical absorbance in the red/near-infrared region of the lightharvesting component(s), as well as their low extinction coefflcient(s). 

Mihailetchi [134] investigated the open circuit voltage of the bulk heterojunction organic solar cells based on methanol-fullerene [6,6]-phenyl C61-butyric acid methyl ester (PCBM) as electron acceptor and poly[2-methoxy-5(3 ,7 -dimethyloctyloxy)-p-phenylene vinylene] (OC1C10-PPV) as an electron donor. It is known that a single layer device follows the MIM model [166] and the open circuit voltage V0c is equal to the difference in the work functions of the metal electrodes [134], If charges accumulate in the... 

Several organics, e.g. pristine poly(3-octylthiophene), polyfluorene, bifunctional spiro compounds and polyphenyleneethynylene derivative, have been used for fabricating photOFETs. Responsivity as high as 0.5-1 A/W has been achieved in some of these transistors. We have already discussed the bulk heterojunction concept in Chapter 5. The bulk heterojunctions are fabricated using acceptor materials with high electron affinity (such as C<5o or soluble derivatives of C6o) mixed with conjugated polymers as electron donors. PhotOFETs based on conjugated polymer/fullerene blends are expected to show... 

C. Melzer, E.J. Koop, V.D. Mihailetchi, P.W.M. Blom, Hole transport in poly(phenylene vinylene)/methanofullerene bulk-heterojunction solar cells, Adv. Fund Mater. 14 (2004) 865-870. 

The first realizations of polymer-polymer bulk heterojunction solar cells were independently reported in the mid-1990s by Yu and Heeger as well as by Halls et al. [28,30]. These solar cells were prepared from blends of two poly(para-phenylenevinylene) (PPV) derivatives the well-known MEH-PPV (poly[2-methoxy-5-(2 -ethylhexyloxy)-l,4-phenylenevinylene]) was used as donor component, while cyano-PPV (CN-PPV) served as acceptor component (identical to MEH-PPV with an additional cyano (- CN) substitution at the vinylene group). The blends showed increased photocurrent and power conversion efficiency (20-100 times) when compared to the respective single component solar cells. 

Similar bulk heterojunctions with CN-PPV as acceptor polymer were realized with poly(3-hexylthiophene) (P3HT or denoted as PAT6 here) and PDPATPSi as donors, leading to a comparable behavior [31]. 

Brabec CJ, Zerza G, Cerullo G, Silvestri SD, Luzzati S, Hummelen JC, Sariciftci S (2001) Tracing photoinduced electron transfer process in conjugated poly-mer/fullerene bulk heterojunctions in real time. Chem Phys Lett 340 232... 

Mihailetchi VD, Roster LJA, Blom PWM, Melzer C, de Boer B, van Duren JKJ, Janssen RAJ (2005) Compositional dependence of the performance of poly(p-phen)dene vinylene) methanofullerene bulk-heterojunction solar cells. Adv Funct Mater 15 795... 

Dennler G, Mozer AJ, Juska G, Pivrikas A, Osterbacka R, Fuchsbauer A, Sariciftci NS (2006) Charge carrier mobility and lifetime versus composition of conjugated poly-mer/fullerene bulk-heterojunction solar cells. Org Electron 7 229... 

Schilinsky P, Asawapirom U, Scherf U, Biele M, Brabec CJ (2005) Influence of the molecular weight of poly(3-hexylthiophene) on the performance of bulk heterojunction solar ceUs. Chem Mater 17 2175... 

Rud JA, Lovell LS, Senn JW, Qiao Q, McLeskey JJT (2005) Water soluble poly-mer/carbon nanotube bulk heterojunction solar cells. J Mater Sci 40 1455... 

Magnetoresistance in Poly (3-hexyl thiophene) Based Diodes and Bulk Heterojunction Solar Cells... 

At the early development of polymer solar cells, a planar p-n junction structure represented the mainstream in mimicking conventional silicon-based solar cells. However, the obtained devices demonstrated poor photovoltaic performances due to the long distance between the exciton and junction interface and insufficient light absorption due to the thin light absorber. It was not until 1995 that the dilemma was overcome with the discovery of a novel bulk heterojunction in which donor and acceptor form interpenetrated phases. Poly[2-methoxy-5-(2 -ethylhexyloxy)-p-phenylene vinylene] was blended with Ceo or its derivatives to form the bulk heterojunction. A much improved power conversion efficiency of 2.9% was thus achieved under the illumination of 20 mW/cm. (Yu et al., 1995). The emergence of the donor/acceptor bulk-heterojunction structure had boosted the photovoltaic performances of polymer solar cells. Currently, a maximal power conversion efficiency of 10.6% had been reported on the basis of synthesizing appropriate polymer materials and designing a tandem structure (You et al., 2013). The detailed discussions are provided in Chapter 5. 

Vanderzande, D., Manca, J.V., 2009. Effect of alkyl side-chain length on photovoltaic properties of poly(3-alkylthiophene)/PCBM bulk heterojunctions. Adv. Funct. Mater. 19,3300-3306. 

Y.-Y. Lin, et al. Interfacial nanostructuring on the performance of poly-mer/TiO nanorod bulk heterojunction solar cells. Journal of the American Chemical Society, 2009. 131(10) p. 3644-3649. 

Hybrid films of ZnO nanoparticles and poly[2-methoxy - 5 - (3, 7 -dimethyloctyloxyl) -1,4-phenylene vinylene] (MDMO-PPV) have been characterized as a model hybrid bulk heterojunction photovoltaic cell [145]. 

Rathgeber S, Perlich J, KAhnlenz F, TArk S, Egbe DA, Hoppe H, et al. Correlation between polymer architecture, mesoscale structure and photovoltaic performance in side-chain-modified poly(p-arylene-ethynyl-ene)-alt-poly(p-arylene-vinylene) PCBM bulk-heterojunction solar cells. Polymer 2011 52(17) 3819-26. 

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