Affiliation:
1. Material Research Center for Energy Systems (MZE) Karlsruhe Institute of Technology (KIT) Kaiserstrasse 12 76131 Karlsruhe Germany
2. Light Technology Institute (LTI) Karlsruhe Institute of Technology (KIT) Kaiserstrasse 12 76131 Karlsruhe Germany
3. Institute of Organic Chemistry (IOC) Karlsruhe Institute of Technology (KIT) Kaiserstrasse 12 76131 Karlsruhe Germany
4. Institute of Nanotechnology (INT) Karlsruhe Institute of Technology (KIT) Kaiserstrasse 12 76131 Karlsruhe Germany
5. Institute of Biological and Chemical Systems – Functional Molecular Systems (IBCS‐FMS) Karlsruhe Institute of Technology (KIT) Kaiserstrasse 12 76131 Karlsruhe Germany
Abstract
AbstractBecause of its excellent hole conductivity, p‐doped 2,2′7,7′‐tetrakis‐(N,N‐di‐p‐methoxyphenyl‐amine)‐9,9′‐spiro‐bifluorene (spiro‐MeOTAD) is commonly deployed for hole transport in organic metal halide perovskite solar cells, but its rather expensive synthesis prompts the research for alternatives. In this work, tetrasubstituted [2.2]paracyclophanes (PCPs) are synthesized and investigated for replacing spiro‐MeOTAD. To enhance their conductivity, different doping strategies are followed. Best conductivities are achieved by doping PCP thin films with tris(2‐(1H‐pyrazol‐1‐yl)‐4‐tert‐butylpyridine)cobalt(III) tris(bis(trifluoromethylsulfonyl)imide) (FK209), matching the conductivity of state‐of‐the‐art p‐doped spiro‐MeOTAD. Best performance in solar cells is leveraged by doping PCPs with the co‐dopants lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) and 4‐tert‐butylpyridine (tBP) which are also used to p‐dope spiro‐MeOTAD thin films in solar cells. Yet, the thermal device stability is maximized upon doping PCPs with FK209 and 2,3,5,6‐tetrafluoro‐7,7,8,8‐tetracyanoquinodimethane (F4TCNQ).
Funder
Carl-Zeiss-Stiftung
Helmholtz Association
Bundesministerium für Bildung und Forschung
Deutsche Forschungsgemeinschaft