Bulk donor-acceptor heterojunction solar

Fig. 3 Contemporary organic solar cell devices are based on donor/acceptor heterojunction device architectures, (a) Energy level diagram, (b) Planar heterojunction conligmation. (c) Bulk heterojunction configuration...

Vandewal K, Tvingstedt K, Gadisa A, Inganas O, Manca JV (2010) Relating the open-circuit voltage to interface molecular properties of donor acceptor bulk heterojunction solar cells. Phys Rev B 81 125204... 

Fig. 5.32. Voc for solar cells using PCBM, azafulleroid 5 and ketolactam 6 as the acceptor component in bulk heterojunction solar cells comprising MDMO-PPV as electron donor...

The observed experimental result that Voc decreases linearly for bulk heterojunction solar cells allows us to conclude that, at least in the high temperature range (T > 200 K), these solar cells may be described by a diode model with Ip exp(E/kT). Here E is a parameter analogous to Eg for conventional semiconductors. For conjugated polymer/fullerene bulk heterojunction solar cells, E should correspond to the energy difference between the HOMO level of the donor and the LUMO level of the acceptor components of the active layer [as also suggested by the extrapolated value of V oc(0 K)]. 

Interpenetrating Network of Donor-Acceptor Organics. Bulk Heterojunction Solar Cells... 

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. 

The ideal schematic structure of a bulk heterojunction solar cell is displayed in Fig. 69. The donor and acceptor phases are interspaced by around... 

Fig. 69 Ideal structure of a donor-acceptor bulk heterojunction polymer solar cell...

The influence of the donor/acceptor ratio on the performance of organic bulk heterojunction solar cells. Presented at the E-MRS spring meeting, Strasbourg... 

Gebeyehu, D., Maennig, B., Drechsel, J., Leo, K., and Pfeiffer, M. 2003. Bulk-heterojunction photovoltaic devices based on donor-acceptor organic small molecule blends. Solar Energy Materials and Solar Cells 79 (l) 81-92. 

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. 

H. Zhou, L. Yang, S. Xiao, S. Liu, W. You, Donor-Acceptor Polymers Incorporating Alkylated Dithienylbenzothiadiazole for Bulk Heterojunction Solar Cells Pronounced Effect of Positioning Alkyl Chains. Macromolecules 2010, 43,811-820. 

J. U. Lee, J. W. Jung, T. Emrick, T. P. Russell, W. H. Jo, Morphology Control of a Polythiophene-Fullerene Bulk Heterojunction for Enhancement of the High-Temperature Stability of Solar Cell Performance by a New Donor-Acceptor Diblock Copolymer. Nanotechnology 2010,21,105201. 

FIGURE 10.8 The energy diagram of the photoinduced electron transfer and the main energy loss mechanisms in donor-acceptor bulk heterojunction solar cells. 

Jenekhe, Watson, and coworkers [277] reported synthesizing three new donor-acceptor conjugated polymers incorporating thieno[3,4-c]pyrrole-4,6-dione acceptor and dialkoxybithiophene or cyclopentadithiophene donor units. The thieno[3,4-c]pyrrole-4,6-dione acceptor containing materials were studied in bulk heterojunction solar cells and organic field-effect transistors. The polymers had... 

Bulk heterojunction solar cell devices were fabricated by Liu and coworkers, using the copolymers as the electron donor and ([6,6 ]-phenyl-C6i-butyric acid methyl ester) as the electron acceptor. The preliminary research has revealed power conversion efficiencies of 0.17-0.59% under AM 1.5 illumination (100 mW/cm ). 

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