Lewis Acid Doping Induced Synergistic Effects on Electronic and Morphological Structure for Donor and Acceptor in Polymer Solar Cells

Abstract

Due to the attraction of optimizing the electronic structure beyond chemical synthesis, molecular doping has recently aroused wide interest in the field of organic solar cells. However, the selection of limited dopants confines its successful application. Inspired by the Lewis base characteristics of the photovoltaic materials, the Lewis acid as novel dopant is introduced in organic solar cells. In both fullerene and nonfullerene based blends, Lewis acid doping leads to increased photovoltaic performance. Detailed experiments reveal that Lewis acid doping has a synergistic effect on modifying the polymer's electronic properties and the acceptor's nanostructure even at low doping concentration, and these are simultaneously responsible for the device improvements. Based on the mechanism studies, it is proposed that the Lewis acid‐doped polymers anions produce induced dipole on the acceptor, this increases the intermolecular interaction and facilitates the morphology optimization. It is believed that the synergistic effect by Lewis acid doping greatly expands the application of doped organic solar cells, in concert with other existing methods to yield higher efficiency values.

Tailoring C60 for Efficient Inorganic CsPbI2Br Perovskite Solar Cells and Modules

“…[40] The tricoordinated organoboron compound tris(pentafluorophenyl) borane (TPFPB) with a vacant p-orbital of the boron atom is a widely used Lewis acid to coordinate with large π-conjugated carbon skeleton materials in organic solar cells. [41] Recently, Luo and co-workers utilized the TPFPB as a Lewis acidic dopant into the Lewis basic poly[bis(4-phenyl)(2,4,6-trimethylphenyl) amine] (PTAA) hole transporting layer (HTL) in PSCs, which formed a PTAA·TPFPB adduct to enhance hole mobility and shifted its HOMO/LUMO level downward. [42] In this study, we propose a codoping strategy using TPFPB and LiClO 4 to tailor the C 60 for fabrication of highly efficient inorganic CsPbI 2 Br PSCs with lower hysteresis.…”

“…In general, introducing a dopant with an electron‐accepting group may be an effective strategy . The tricoordinated organoboron compound tris(pentafluorophenyl)borane (TPFPB) with a vacant p‐orbital of the boron atom is a widely used Lewis acid to coordinate with large π‐conjugated carbon skeleton materials in organic solar cells . Recently, Luo and co‐workers utilized the TPFPB as a Lewis acidic dopant into the Lewis basic poly[bis(4‐phenyl)(2,4,6‐trimethylphenyl)amine] (PTAA) hole transporting layer (HTL) in PSCs, which formed a PTAA·TPFPB adduct to enhance hole mobility and shifted its HOMO/LUMO level downward …”

Addition of the Lewis Acid Zn(C6F5)2 Enables Organic Transistors with a Maximum Hole Mobility in Excess of 20 cm2 V−1 s−1

“…It is the emergence of these new energy states that then facilitate the charge transfer processes resulting in p ‐doping . This mechanism has been used to explain the results in a number of recent studies involving B(C 6 F 5 ), where redistribution in the electron density in the semiconductor, caused by the interaction(s) between B in B(C 6 F 5 ) 3 ) and nitrogen (N) lone pairs in the organic semiconductor, results in p ‐doping …”

“…Over the past few years the Lewis acid tris(pentafluorophenyl)borane [B(C 6 F 5 ) 3 ] was shown to offer an alternative approach to p ‐doping of OSCs . In several of these studies the benefits of incorporating B(C 6 F 5 ) 3 were shown to be twofold: p ‐doping while simultaneously altering the OSC layer's microstructure, with the latter effect drastically enhancing the semiconductor's crystallinity and charge carrier transport .…”

“…Although many questions still surround the fundamental mechanisms involved in B(C 6 F 5 ) 3 ‐induced p ‐doping, morphology change, and the relationship between the two effects, there is clear evidence that one or more synergistic mechanisms are responsible for improving the electrical performance of different electronic devices—not just OTFTs . For example, simple addition of B(C 6 F 5 ) 3 has shown to improve the performance of organic light emitting diodes, OTFT sensors, batteries, organic photovoltaics, and perovskite photovoltaics . In OTFTs, the simultaneous effects of p ‐doping and morphology changes resulted in greatly increased charge carrier hole mobility ( µ ) .…”