Metal Ion/Dendrimer Complexes with Tunable Work Functions in a Wide Range and Their Application as Electron‐ and Hole‐Transport Materials of Non‐Fullerene Organic Solar Cells |
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| Authors: | Zhimeng Yu Bichen Li Jianyong Ouyang |
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| Affiliation: | 1. Department of Materials Science and Engineering, National University of Singapore, Singapore, Singapore;2. Solar Energy Research Institute of Singapore (SERIS), National University of Singapore, Singapore, Singapore |
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| Abstract: | The work functions of electrodes can be modified by adding charge transport layers to have good energy level matching with the active materials for organic solar cells (OSCs). Usually, a certain material gives rise to one definite work function of an electrode. In this work it is demonstrated that complexes of poly(amido amine) (generation 3) (PAMAM) with Cu2+ can continuously tune the work function of indium tin oxide (ITO) in a range of 4–5 eV by controlling the ratio of Cu2+ to PAMAM. PAMAM can lower the work function of ITO from 4.60 to 4.07 eV, while Cu2+‐PAMAM can increase the work function. The work function increase depends on the Cu2+‐to‐PAMAM molar ratio, and the work function can be up to 4.96 eV. The Cu2+ effect is ascribed the Cu2+‐caused change in the dipole moment of PAMAM. Moreover, this method can be used to continuously modify the work function of other materials, including Ag, Au, poly(3,4‐ethylenedioxythiophene):polystyrene sulfonate, and reduced graphene oxide. In addition, PAMAM and Cu2+‐PAMAM are investigated as the charge collection buffer materials of non‐fullerene OSCs of poly(2,6‐(4,8‐bis(5‐(2‐ethylhexyl)thiophen‐2‐yl)‐benzo1,2‐b:4,5‐b′]dithiophene))‐alt‐(5,5‐(1′,3′‐di‐2‐thienyl‐5′,7′‐bis(2‐ethylhexyl)benzo1′,2′‐c:4′,5′‐c′]dithiophene‐4,8‐dione))]: 3,9‐bis(2‐methylene‐(3‐(1,1‐dicyanomethylene)‐indanone))‐5,5,11,11‐tetrakis(4‐hexylphenyl)‐dithieno2,3‐d:2′,3′‐d′]‐s‐indaceno1,2‐b:5,6‐b′]dithiophene). The power conversion efficiency can reach 9.2%, which is comparable to that using conventional charge transport materials. |
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| Keywords: | ITO metal complexes organic solar cells poly(amido amine) PAMAM work function |
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