Doped Copper Phthalocyanine via an Aqueous Solution Process for Normal and Inverted Perovskite Solar Cells
Jin-Miao Wang, Zhao-Kui Wang,* Meng Li, Cong-Cong Zhang, Lu-Lu Jiang, Ke-Hao Hu, Qing-Qing Ye, and Liang-Sheng Liao*
Jiangsu Key Laboratory for Carbon-Based Functional Materials and Devices Institute of Functional Nano and Soft Materials (FUNSOM) Soochow University, Suzhou 215123, China
Great efforts toward developing novel and efficient hole-transporting materials are needed to further improve the device efficiency and enhance the cell stability of perovskite solar cells (PSCs). The poor film conductivity and the low carrier mobility of organic small-molecule-based hole-transporting materials restrict their application in PSCs. This study develops an efficient and stable hole-transporting material, tetrafluorotetracyanoquinodimethane(F4-TCNQ)-doped copper phthalocyanine-3,4′,4′′,4′′′-tetra-sulfonated acid tetra sodium salt (TS-CuPc) via a solution process, in planar structure PSCs.The p-type-doped TS-CuPc film demonstrates improved film conductivity and hole mobility owing to the strong electron affinity of F4-TCNQ. By theF4-TCNQ tailoring, the composite film gives the highest occupied molecular orbital level as high as 5.3 eV, which is beneficial for hole extraction. In addition, the aqueous solution processed TS-CuPc:F4-TCNQ precursor is almost neutral with good stability for avoiding the electrode erosion. As a result, the fabricated PSCs employing TS-CuPc:F4-TCNQ as the hole-transporting material exhibit a power conversion efficiency of 16.14% in a p–i–n structure and 20.16% in an n–i–p structure, respectively. The developed organic small molecule of TS-CuPc provides the diversification of hole-transporting materials in planar PSCs.