Favorable electronic structure for organic solar cells induced by strong interaction at interface

Wang, Shenghao; Sakurai, Takayasu; Hao, Xia; Fu, Wei; Masuda, S.; Akimoto, Katsuhiro

doi:10.1063/1.4829905

Cited by 8 publications

(5 citation statements)

References 20 publications

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“…The binding energy between the BCP and Ag is 0.15 eV calculated as the difference in the total energy. The predicted molecular structure is consistent with the recent X-ray photoemission study on BCP and Mg complex where a strong bond between the nitrogen atoms of BCP and the metal atom was suggested …”

Section: Resultssupporting

confidence: 89%

Electron Transport in Bathocuproine Interlayer in Organic Semiconductor Devices

Yoshida

2015

J. Phys. Chem. C

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When a thin layer of bathocuproine (BCP) is inserted between the metal electrode and organic layer of organic semiconductor device, the electron injection/collection efficiency at the interface is significantly improved. However, the mechanism of electron transport through the BCP layer has not been clarified yet. In this study, we directly observed the unoccupied electronic states of the Ag/BCP interface using low-energy inverse photoemission spectroscopy. The result shows that Ag strongly interacts with the BCP molecule and the lowest unoccupied molecular orbital (LUMO) level of the Ag-BCP complex aligns with the Fermi level indicating that the electron transport occurs through the LUMO level of the complex. With the aid of DFT calculation, we identify the reaction product

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Section: Resultssupporting

confidence: 89%

Electron Transport in Bathocuproine Interlayer in Organic Semiconductor Devices

Yoshida

2015

J. Phys. Chem. C

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“…15,16) In our previous work, we have clarified the electronic properties of BCP=metal interface. [17][18][19] We also have demonstrated that BCP can be used as a buffer layer in inverted OSCs. 20) However, the function of BCP in an inverted OSC is still not yet fully understood.…”

Section: Introductionmentioning

confidence: 84%

Effect of bathocuproine buffer layer in small molecule organic solar cells with inverted structure

Hao

Wang

Sakurai

et al. 2015

Jpn. J. Appl. Phys.

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Inverted organic solar cells (OSCs) based on boron subphthalocynine chloride (SubPc) and fullerene (C 60 ) were fabricated and the device structure was optimized by inserting a bathocuproine (C 26 H 20 N 2 ) buffer layer. The power conversion efficiency was greatly improved from 0.8 to 1.6%. The roles of bathocuproine in this inverted device were investigated by photoluminescence and transient photovoltage/photocurrent measurements. The results show that the bathocuproine in the device not only blocks the exciton quenching, but also prohibits the build-up of charge trapping and suppresses the trap-assisted recombination.

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“…In addition, the origin of the gap states is the Al-BCP complex formation. 14 The unoccupied gap states should act as a transport level from C 60 to the Al cathode since the BCP LUMO is energetically too far to accept electrons. From the well-matched theoretical results with the UPS and IPES measurements, the formation of the Al-BCP complex giving occupied and unoccupied gap states in the original band gap of BCP is confirmed.…”

Section: B Theoretical Studymentioning

confidence: 99%

“…To determine the transport levels of BCP, the electronic structures of the Al/BCP interface have been studied and interfacial gap states have been reported. [14][15][16][17] In addition, Nakayama et al reported another gap state at the BCP/C 60 interface. 18 However, in these studies, only occupied gap states below the Fermi level (E F ) were measured, which are not an associated level for electron transport directly.…”

Section: Introductionmentioning

confidence: 99%

Electron transport mechanism of bathocuproine exciton blocking layer in organic photovoltaics

Lee

Park

Lee

et al. 2016

Phys. Chem. Chem. Phys.

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Efficient exciton management is a key issue to improve the power conversion efficiency of organic photovoltaics (OPVs). It is well known that the insertion of an exciton blocking layer (ExBL) having a large band gap promotes the efficient dissociation of photogenerated excitons at the donor-acceptor interface. However, the large band gap induces an energy barrier which disrupts the charge transport. Therefore, building an adequate strategy based on the knowledge of the true charge transport mechanism is necessary. In this study, the true electron transport mechanism of a bathocuproine (BCP) ExBL in OPVs is comprehensively investigated by in situ ultraviolet photoemission spectroscopy, inverse photoemission spectroscopy, density functional theory calculation, and impedance spectroscopy. The chemical interaction between deposited Al and BCP induces new states within the band gap of BCP, so that electrons can transport through these new energy levels. Localized trap states are also formed upon the Al-BCP interaction. The activation energy of these traps is estimated with temperature-dependent conductance measurements to be 0.20 eV. The Al-BCP interaction induces both transport and trap levels in the energy gap of BCP and their interplay results in the electron transport observed.

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Favorable electronic structure for organic solar cells induced by strong interaction at interface

Abstract: Articles you may be interested inEffect of co-adsorption dye on the electrode interface (Ru complex/TiO2) of dye-sensitized solar cells AIP Advances 3, 072113 (2013);

Cited by 8 publications

References 20 publications

Electron Transport in Bathocuproine Interlayer in Organic Semiconductor Devices

Electron Transport in Bathocuproine Interlayer in Organic Semiconductor Devices

Effect of bathocuproine buffer layer in small molecule organic solar cells with inverted structure

Electron transport mechanism of bathocuproine exciton blocking layer in organic photovoltaics

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