Efficient polymer nanocrystal hybrid solar cells by improved nanocrystal composition

Zhou, Yun; Eck, Michael J.; Men, Cong; Rauscher, Frank; Niyamakom, Phenwisa; Yilmaz, Seyfullah; Dumsch, Ines; Allard, Sybille; Scherf, Ullrich; Krüger, Michael

doi:10.1016/j.solmat.2011.07.015

Cited by 48 publications

(30 citation statements)

References 27 publications

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“…Higher electron-transfer rates from the polymer-dot fi lms may be obtained via mild QD ligand-exchange processes such as those reported in recent demonstrations of effi cient polymer-PbS QD solar cells. [15][16][17][18][19][20] QD emission quenching was also investigated to probe charge transfer originating in the QDs. In the steady-state experiments the PL was quasi-resonantly excited at 850 nm so excitations were photogenerated solely in the QD component of the blends.…”

Section: Full Papermentioning

confidence: 99%

“…The composition was chosen based on optimization studies of previously reported hybrid photodiodes. [ 24 ] Hybrid solar cells require in general higher QD loadings up to 90% wt [15][16][17][18][19][20] however the simultaneous tuning of the QD size and blend in a wide range is impractical so the infl uence of the latter will be studied elsewhere. Binary and ternary fi lms as well as reference pristine nanocrystal and polymer fi lms were deposited on quartz substrates using a doctor-blade technique under ambient conditions.…”

Section: Full Papermentioning

confidence: 99%

“…Control over blend nanomorphology [11][12][13][14][15] and the shape and aspect ratio of the NCs [ 11-13 , 16 ] has proven to be critical in improving performance. A further increase in effi ciency was enabled by two important developments: i) the use of mild postfabrication chemical treatments to replace bulky insulating QD ligands with shorter capping molecules to allow better charge extraction [15][16][17][18][19][20] and ii) the employment of new low-bandgap copolymers. [15][16][17][18][19][20][21][22] The photophysics of bulk heterojunctions of a high-performance, low-gap silicon-bridged dithiophene polymer with oleic acid capped PbS quantum dots (QDs) are studied to assess the material potential for light harvesting in the visible-and IR-light ranges.…”

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confidence: 99%

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Size‐Dependent Charge Transfer in Blends of PbS Quantum Dots with a Low‐Gap Silicon‐Bridged Copolymer

Itskos

Papagiorgis

Τσόκκου

et al. 2013

Advanced Energy Materials

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overcoming several key obstacles, and achieving more than two orders of magnitude effi ciency increase towards the anticipated milestone solar cell effi ciency of 10%. [ 1,2 ] Equally impressive has been the progress in light harvesting based on colloidal quantum dots (QDs) with successful demonstrations based on all-QD active regions of Schottky [ 3,4 ] solar cells and recently of depleted heterojunction [ 5 ] and p-n junction [ 6 ] types of devices. While high-performance light sensors can be produced based on fully organic or fully nanocrystal active regions, composites of the two systems exhibit important advantages. Organic devices can benefi t from the higher absorption of nanocrystals (NCs) compared to the fullerene acceptors, size-tunable levels to tailor band-offsets, control over NC shape to optimize composite morphologies, and the possibility of higher stability arising from the incorporation of a less-volatile inorganic moiety. For QD devices an extended network of highly absorbing conducting organic components can signifi cantly enhance light harvesting and can provide pathways for effi cient charge, energy, and even multiexciton extraction. [ 7,8 ] The seminal proposal by Alivisatos and co-workers [ 9 ] to replace fullerenes with colloidal quantum dots (QDs) as the acceptor material in organic bulk heterojunctions (BHJs) paved the way for hybrid polymer-nanocrystal structures. Research on hybrid PVs intensifi ed with the publication of another article by the same group demonstrating a power conversion efficiency (PCE) of over 2% by using a mixture of CdSe NCs and P3HT as the active layer in a BHJ architecture. [ 10 ] Numerous reports followed, i.e. see recent reviews, [ 11,12 ] mainly based on Cd chalcogenide quantum dots and phenylenevinylene (PPV) and polythiophene (P3HT) conjugated polymers. Control over blend nanomorphology [11][12][13][14][15] and the shape and aspect ratio of the NCs [ 11-13 , 16 ] has proven to be critical in improving performance. A further increase in effi ciency was enabled by two important developments: i) the use of mild postfabrication chemical treatments to replace bulky insulating QD ligands with shorter capping molecules to allow better charge extraction [15][16][17][18][19][20] and ii) the employment of new low-bandgap copolymers. [15][16][17][18][19][20][21][22] The photophysics of bulk heterojunctions of a high-performance, low-gap silicon-bridged dithiophene polymer with oleic acid capped PbS quantum dots (QDs) are studied to assess the material potential for light harvesting in the visible-and IR-light ranges. By employing a wide range of nanocrystal sizes, systematic dependences of electron and hole transfer on quantum-dot size are established for the fi rst time on a low-gap polymer-dot system. The studied system exhibits type II band offsets for dot sizes up to ca. 4 nm, whch allow fast hole transfer from the quantum dots to the polymer that competes favorably with the intrinsic QD recombination. Electron transfer from the polymer is also observed although i...

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Section: Full Papermentioning

confidence: 99%

Section: Full Papermentioning

confidence: 99%

mentioning

confidence: 99%

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Size‐Dependent Charge Transfer in Blends of PbS Quantum Dots with a Low‐Gap Silicon‐Bridged Copolymer

Itskos

Papagiorgis

Τσόκκου

et al. 2013

Advanced Energy Materials

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“…They studied charge [29] or zinc oxide [30], medium bandgap materials like cadmium sulfide [31], selenide [8,32,33] or telluride [34], copper indium sulfide [35] and selenide [36], as well as low band gap materials like lead sulfide [6], or selenide [37]. Recently, also other abundant and non-toxic materials like SnS 2 [38], FeS 2 [39] or Bi 2 S 3 [40] as well as silicon nanoparticles [41] have been researched concerning the incorporation in hybrid solar cells.…”

Section: Introductionmentioning

confidence: 99%

In situ syntheses of semiconducting nanoparticles in conjugated polymer matrices and their application in photovoltaics.

Rath¹,

Trimmel²

2014

Hybrid Materials

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Hybrid solar cells based on conjugated polymers and inorganic semiconducting nanoparticles combine beneficial properties of organic and inorganic semiconductors and are, therefore, an exciting alternative to pure organic or inorganic solar cell technologies. Several approaches for the fabrication of hybrid solar cells are already elaborated and explored. In the last years routes have emerged, where the nanoparticles are prepared directly in the matrix of the conjugated polymer. Here, the conjugated polymer prevents the nanoparticles from excessive growth and thereby makes additional capping agents obsolete. This review focuses on in situ preparation methods of inorganic semiconducting nanoparticles in conjugated polymers in view of applications in hybrid solar cells. The details, advantages and disadvantages of the different in situ methods are critically examined and put in comparison to the classical route where pre-synthesized nanoparticles are used. Various key factors influencing the solar cell performance as well as future strategies for increasing the overall efficiency of hybrid solar cells prepared via in situ routes are discussed. KeywordsInorganic-organic hybrid solar cell • Nanocomposite • OPV

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“…The decrease of R s may be attributed to the effective circumvention of charge transport by hopping for larger-sized NPs. [ 28 ] In addition, less capped citrate ions of the larger-sized NPs signify less electron trap which contributes to the low resistance. For comparison, the R s of vacuum evaporated gold fi lm with the thickness of 60 nm is also measured.…”

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confidence: 99%

Dip‐Coated Gold Nanoparticle Electrodes for Aqueous‐Solution‐Processed Large‐Area Solar Cells

Chen

et al. 2014

Advanced Energy Materials

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gold NPs monolayer was introduced on the interface between the water and n-hexane and then dip-coating technique was adopted to generate a large area gold NPs fi lm ( Scheme 1 ). Fabricating a 2D gold fi lm by this water/oil method was proposed in past work. [ 24,25 ] However, to the best of our knowledge, this is the fi rst time to investigate it as an electrode for solar cells. It is worth noting that when 15 nm and 35 nm gold NPs were used to generate the multilayer gold fi lms, thermal treatment was required to avoid the dissolution of gold fi lm by subsequent dip-coating process. Nevertheless, in the case of 60nm gold NPs, stewing the fi lm in air for a while was enough for the next layer dip-coating. We attribute this phenomenon to the different solubility of gold NPs with varying size. Relatively, the smaller NPs have more citrate ions capped than the bigger NPs and possess better solubility. Upon annealing, the gold NPs fi lm would experience processes of melting, interparticle coalescence and dewetting, [ 26 ] thus making it more hydrophobic. As for the 60 nm gold NPs, with less citrate ions capping, lower solubility and larger size made the fi lm difficult to dissolve in water after stewing in the air for a while.The electric resistance of gold fi lms with different NP sizes and different dip-coated layers (1, 2, 3, and 4) was investigated previously. Figure 1 shows the electric resistance of the gold NPs fi lms measured by the four-point probe meter. Detailed information is shown in Table 1 . The electric resistance decreases dramatically when the layer number of gold fi lms increases. In the case of the 60 nm gold NPs, the electric resistance values are 897 Ω/ٗ, 4.5 Ω/ٗ, 2 Ω/ٗ and 1.3 Ω/ٗ respectively for 1 to 4 layers. To illustrate this relationship, TEM and scanning electron microscopy (SEM) characterizations ( Figure 2 ) are conducted. For one layer, the gold nanoparticles are assembled incompactly with inhomogeneously interparticle distances, which are adverse for electron transfer. Due to the inhomogeneous arrangement of NPs in the monolayer, the R s values show slight fl uctuation when different positions of the fi lms are measured. As more layers are dip-coated, the interparticle distances become much smaller, which is in accordance with the decrease in R s . Moreover, the R s values measured in different positions of the fi lms become more stable. The gold fi lms with three layers and four layers show similar R s values, both of which are very small. As shown

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Efficient polymer nanocrystal hybrid solar cells by improved nanocrystal composition

Cited by 48 publications

References 27 publications

Size‐Dependent Charge Transfer in Blends of PbS Quantum Dots with a Low‐Gap Silicon‐Bridged Copolymer

Size‐Dependent Charge Transfer in Blends of PbS Quantum Dots with a Low‐Gap Silicon‐Bridged Copolymer

In situ syntheses of semiconducting nanoparticles in conjugated polymer matrices and their application in photovoltaics.

Dip‐Coated Gold Nanoparticle Electrodes for Aqueous‐Solution‐Processed Large‐Area Solar Cells

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