Cascade energy transfer versus charge separation in ladder-type oligo(<i>p</i>-phenylene)/ZnO hybrid structures for light-emitting applications

Bianchi, Francesco; Sadofev, Sergey; Schlesinger, Raphael; Kobin, Björn; Hecht, Stefan; Koch, Norbert; Henneberger, F.; Blumstengel, S.

doi:10.1063/1.4903517

Cited by 13 publications

(23 citation statements)

References 25 publications

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“…In organic/inorganic hybrid systems, for instance, their major advantages for optoelectronic applications are seen in the strong light-matter coupling of the organic components, while the inorganic counterparts excel in large carrier mobilities and thus efficient charge-carrier transport as well as small exciton binding energies. [6][7][8][9][10] Prerequisite for that is the lightinduced creation of hybrid or charge-transfer excitons, which exhibit the hole to a large extent on one side of the interface while the excited electron would reside on the other side. [4,5] Type-II alignment, in turn, is favored for a hybrid solar cell where optical absorption of sunlight is expected to directly lead to electron-hole separation.…”

Section: Introductionmentioning

confidence: 99%

Electronic and Optical Excitations at the Pyridine/ZnO(101¯0) Hybrid Interface

Turkina

Nabok

Guļāns

et al. 2018

Advcd Theory and Sims

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By combining all-electron density-functional theory with many-body perturbation theory, a prototypical inorganic/organic hybrid system, composed of pyridine molecules that are chemisorbed on the nonpolar ZnO(1010) surface is investigated. The G 0 W 0 approximation is employed to describe its one-particle excitations in terms of the quasiparticle band structure, and the Bethe-Salpeter equation is solved to obtain the absorption spectrum. The different character of the constituents leads to very diverse self-energy corrections of individual Kohn-Sham states, and thus the G 0 W 0 band structure is distinctively different from its DFT counterpart, that is, many-body effects cannot be regarded as a rigid shift of the conduction bands. The nature of the optical excitations at the interface over a wide energy range is explored and it is shown that various kinds of electron-hole pairs are formed, comprising hybrid excitons and (hybrid) charge-transfer excitations. The absorption onset is characterized by a strongly bound brightZnO-dominated hybrid exciton. For the selected examples of either exciton type, the individual contributions from the valence and conduction bands are analyzed and the binding strength and extension of the electron-hole wavefunctions are discussed.

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Section: Introductionmentioning

confidence: 99%

Electronic and Optical Excitations at the Pyridine/ZnO(101¯0) Hybrid Interface

Turkina

Nabok

Guļāns

et al. 2018

Advcd Theory and Sims

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“…The selective contacts employed in the device support both mechanisms. The phenomenon of competing charge-and energy-transfer processes is common in hybrid inorganic-organic systems, 57,58 where the rates of the two processes depend critically on the energy level alignment (ELA) at the interface, along with a host of other factors. 59 The present hybrid interface, where c-Si abuts a triplet exciton-bearing organic film, makes for a complicated system that is yet to be fully understood.…”

Section: Introductionmentioning

confidence: 99%

Crystalline silicon solar cells with tetracene interlayers: the path to silicon-singlet fission heterojunction devices

et al. 2018

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Singlet exciton fission is an exciton multiplication process that occurs in certain organic materials, converting the energy of single highly-energetic photons into pairs of triplet excitons. This could be used to boost the conversion efficiency of crystalline silicon solar cells by creating photocurrent from energy that is usually lost to thermalisation. An appealing method of implementing singlet fission with crystalline silicon is to incorporate singlet fission media directly into a crystalline silicon device. To this end, we developed a solar cell that pairs the electron-selective contact of a high-efficiency silicon heterojunction cell with an organic singlet fission material, tetracene, and a PEDOT:PSS hole extraction layer. Tetracene and n-type crystalline silicon meet in a direct organic-inorganic heterojunction. In this concept the tetracene layer selectively absorbs blue-green light, generating triplet pairs that can dissociate or resonantly transfer at the organo-silicon interface, while lower-energy light is transmitted to the silicon absorber. UV photoemission measurements of the organicinorganic interface showed an energy level alignment conducive to selective hole extraction from silicon by the organic layer. This was borne out by current-voltage measurements of devices subsequently produced. In these devices, the silicon substrate remained well-passivated beneath the tetracene thin film. Light absorption in the tetracene layer created a net reduction in current for the solar cell, but optical modelling of the external quantum efficiency spectrum suggested a small photocurrent contribution from the layer. This is a promising first result for the direct heterojunction approach to singlet fission on crystalline silicon.

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“…[51,52] With an increasing number of spiro groups, the optical gap for absorption and emission slightly decreases, which is disadvantageous with respect to resonant energy transfer with ZnO.…”

Section: Resultsmentioning

confidence: 99%

Spiro‐Bridged Ladder‐Type Oligo(para‐phenylene)s: Fine Tuning Solid State Structure and Optical Properties

Kobin

Schwarz

Braun‐Cula

et al. 2017

Adv Funct Materials

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A set of ladder-type quaterphenyls with an incremental number of spiro-bifluorene units in the bridge positions as well as an in-plane bent quaterphenyl carrying all bridges on one and the same side of the ribbon are synthesized and characterized. While spiro-bifluorene substituents lead to bathochromically shifted maxima in the UV-vis absorption spectra, this effect can be compensated by in-plane bending. The influence of different deposition techniques on the solid state structure is analyzed by X-ray diffraction of single crystals obtained by crystallization from solution as well as sublimation. An increasing number of spiro-bifluorene substituents are found to aid thin-film formation.

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Cascade energy transfer versus charge separation in ladder-type oligo(p-phenylene)/ZnO hybrid structures for light-emitting applications

Cited by 13 publications

References 25 publications

Electronic and Optical Excitations at the Pyridine/ZnO(101¯0) Hybrid Interface

Electronic and Optical Excitations at the Pyridine/ZnO(101¯0) Hybrid Interface

Crystalline silicon solar cells with tetracene interlayers: the path to silicon-singlet fission heterojunction devices

Spiro‐Bridged Ladder‐Type Oligo(para‐phenylene)s: Fine Tuning Solid State Structure and Optical Properties

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