Affiliation:
1. Institute of Organic Chemistry (IOC) Karlsruhe Institute of Technology (KIT) Fritz‐Haber‐Weg 6 76131 Karlsruhe Germany
2. Institute of Nanotechnology (INT) Karlsruhe Institute of Technology (KIT) Kaiserstraße 12 76131 Karlsruhe Germany
3. Light Technology Institute (LTI) Karlsruhe Institute of Technology (KIT) Engesserstrasse 13 76131 Karlsruhe Germany
4. Material Research Center for Energy Systems (MZE) Karlsruhe Institute of Technology (KIT) Strasse am Forum 7 76131 Karlsruhe Germany
5. Institute of Biological and Chemical Systems – Functional Molecular Systems (IBCS‐FMS) Karlsruhe Institute of Technology (KIT) Hermann‐von‐Helmholtz‐Platz 1 76344 Eggenstein‐Leopoldshafen Germany
Abstract
Abstract2,2′,7,7′‐Tetrakis(N,N‐di‐p‐methoxyphenylamine)−9,9′‐spirobifluorene (spiro‐OMeTAD) is the prevalent hole transport layer in perovskite solar cells (PSCs) with regular device architecture. Yet, its spirobifluorene core and multistep synthesis make it rather expensive. For the further technological success of PSCs, novel scalable and inexpensive alternative hole transport layers are needed. Herein, a study of the structure‐property relations of pseudo‐para‐substituted [2.2]paracyclophanes is presented. Eight different hole transport materials are synthesized via double CH activation, eliminating metal‐containing substituents for cross‐coupling reactions. The ionization potentials (IPs) of the disubstituted paracyclophanes (DiPCPs) are examined by photoelectron spectroscopy in air, cyclic voltammetry and theoretical calculations. Through variation of donor groups and π‐linkers, IPs that span a range from 5.14 to 5.86 eV are achieved, demonstrating high customizability. From the eight novel materials, five showed good solubility and are implemented into PSCs. The solar cells with a hole transport layer of undoped 4,16‐di(4‐(2‐thienyl)‐N,N‐bis(4‐methoxyphenyl)aniline)[2.2]paracyclophane (DiPCP‐2) exhibit a power conversion efficiency of 12.7% ± 0.4%. The facile synthesis of DiPCP‐2 enables an estimated cost reduction by two thirds compared to spiro‐OMeTAD.
Funder
Deutsche Forschungsgemeinschaft
Carl-Zeiss-Stiftung
Deutsche Bundesstiftung Umwelt
Subject
Electrochemistry,Condensed Matter Physics,Biomaterials,Electronic, Optical and Magnetic Materials