Multiple Charge Transfer States in Donor–Acceptor Heterojunctions with Large Frontier Orbital Energy Offsets
| Autor: | Bjoern Niesen, Yoann Olivier, Terry Chien-Jen Yang, Michael A. Fusella, Xiao Liu, Saeed Uz Zaman Khan, Alyssa N. Brigeman, Barry P. Rand, Noel C. Giebink, David Beljonne, Jordan T. Dull, Gabriele D'Avino, Luca Muccioli, Giacomo Londi |
|---|---|
| Přispěvatelé: | Princeton University, University of Mons [Belgium] (UMONS), Théorie de la Matière Condensée (TMC ), Institut Néel (NEEL), Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019])-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019]), Laboratoire de Chimie des Polymères Organiques (LCPO), Centre National de la Recherche Scientifique (CNRS)-Institut Polytechnique de Bordeaux-Ecole Nationale Supérieure de Chimie, de Biologie et de Physique (ENSCBP)-Université de Bordeaux (UB)-Institut de Chimie du CNRS (INC), IMT Neuchâtel (IMT), Université de Neuchâtel (UNINE)-IMT, Université de Mons (UMons), Khan, Saeed-Uz-Zaman, Londi, Giacomo, Liu, Xiao, Fusella, Michael A., D’Avino, Gabriele, Muccioli, Luca, Brigeman, Alyssa N., Niesen, Bjoern, Yang, Terry Chien-Jen, Olivier, Yoann, Dull, Jordan T., Giebink, Noel C., Beljonne, David, Rand, Barry P. |
| Jazyk: | angličtina |
| Rok vydání: | 2019 |
| Předmět: |
separation
Work (thermodynamics) Materials science General Chemical Engineering 02 engineering and technology organic solar-cells 010402 general chemistry 01 natural sciences Molecular physics hot exciton dissociation generation crystals Materials Chemistry Range (particle radiation) Charge (physics) Heterojunction dependence General Chemistry [CHIM.MATE]Chemical Sciences/Material chemistry 021001 nanoscience & nanotechnology 0104 chemical sciences Amorphous solid Specific orbital energy open-circuit voltage efficiency [PHYS.COND.CM-MS]Physics [physics]/Condensed Matter [cond-mat]/Materials Science [cond-mat.mtrl-sci] 0210 nano-technology Donor acceptor high bandgap absorption force |
| Zdroj: | Chemistry of Materials Chemistry of Materials, American Chemical Society, 2019, 31 (17), pp.6808-6817. ⟨10.1021/acs.chemmater.9b01279⟩ |
| ISSN: | 0897-4756 1520-5002 |
| DOI: | 10.1021/acs.chemmater.9b01279 |
| Popis: | International audience; In this work, we demonstrate several organic amorphous donor−acceptor systems that exhibit sub-bandgap features over a more than 2 eV spectral range. An in-depth study of one of these systems, NPB:HAT-CN (NPB is N,N′-di(1-naphthyl)-N,N′-diphenyl-(1,1′-biphenyl)-4,4′-diamine and HAT-CN is 1,4,5,8,9,11-hexaazatriphenylenehexacarbonitrile), reveals that the broad sub-bandgap features are attributed to multiple electronic charge transfer (CT) state transitions, broadened by energetic disorder sourcing from the fluctuations of intramolecular conformations and by the disordered intermolecular environment. These unique CT features originate from an unconventional donor and acceptor selection that reveals new insight about photocurrent generation and nonradiative recombination. Unlike materials employed in high performing organic solar cells, the materials studied here feature large optical energy gaps with very large frontier orbital energy level offsets, creating high bandgap devices with low open-circuit voltage. In addition to multiple electronic CT levels, we reveal that the internal quantum efficiency of these multiple CT transitions is not constant but photon energy dependent and with photoluminescence that originates primarily from the second lowest electronic CT state implying slow (relative to radiative and nonradiative rates) internal conversion within the CT manifold. Overall, this class of donor−acceptor pairs provides an opportunity to probe CT states in unique ways to potentially unravel their role in carrier generation−recombination and energy loss mechanisms. ■ INTRODUCTION With more than 15% power conversion efficiency recently achieved 1 and coupled with the ability to be grown on flexible substrates on a large scale with low-cost fabrication techniques, organic solar cells are making a strong case for energy conversion applications. Most advances in power conversion efficiency are the result of impressive material and interface engineering and innovation. However, due to the lack of a complete understanding and consensus of carrier generation and recombination processes as well as loss mechanisms at charge generating donor−acceptor (D-A) interfaces, 2 the actual limits of organic solar cell performance remain unknown. In this context, intermolecular charge transfer (CT) excitations at D−A interfaces play an important role in the photophysical processes and energy losses of organic solar cells. 3−6 In order to understand how carrier generation and recombination are affected by CT states, a better comprehension of their origin and energetic distribution is crucial. More specifically, some key issues that are currently under inquiry include whether the carrier dissociation efficiency Special Issue: Jean-Luc Bredas Festschrift |
| Databáze: | OpenAIRE |
| Externí odkaz: |
|