A Pyrrole-Bridged Bis(oxa[5]helicene)-Based Molecular Semiconductor for Efficient and Durable Perovskite Solar Cells: Microscopic Insights

Abstract

Exotic organic semiconductors based on helicenes are attractive because of their peculiar topology-related optoelectronic properties and good solution-processability. We herein construct pyrrole-bridged bis­(oxa[5]­helicene) and further employ it as the π-linker of a solution-processable molecular semiconductor (DOP-OMeDPA) with improved hole mobility and glass transition temperature compared with its oxa[5]­helicene counterpart. A solution-processed, doped semiconducting composite of DOP-OMeDPA presents high conductivity and slow interfacial charge recombination in perovskite solar cells, enabling the fabrication of thermostable devices with 21.3% efficiency. The DOP-OMeDPA-based thin film exhibits excellent morphology stability at 60 °C and remarkably attenuates the thermal decomposition of perovskite. Molecular dynamics modeling uncovers the microscopic origin of glass transition, that is, the torsional vibration of electron-donor for pristine materials, compared with the translational motion of molecules in doped ones.

An S-shaped double helicene showing both multi-resonance thermally activated delayed fluorescence and circularly polarized luminescence

“…Beyond chiroptical properties the high solubility of helicenes in organic solvents (compared to planar acenes), coupled with their excellent thermal stability has led to a wider array of optoelectronic applications, including as hole-transport materials in photovoltaic devices. 26–28…”

“…Beyond chiroptical properties the high solubility of helicenes in organic solvents (compared to planar acenes), coupled with their excellent thermal stability has led to a wider array of optoelectronic applications, including as hole-transport materials in photovoltaic devices. [26][27][28] Thermally activated delayed fluorescence (TADF) materials have become increasingly attractive as sensors, 29 in lasers, 30 photodetectors, 31 photocatalysis 32 and bioimaging 33 as well as both emitters and hosts in organic light-emitting diodes (OLEDs) 34 due to their ability to harvest 100% of electrically generated excitons to generate light. This is accomplished by conversion of triplet excitons into singlets via reverse intersystem crossing (RISC) [34][35][36][37][38] enabled by their small S 1 -T 1 energy gap, DE ST .…”

Intrinsic Dynamic and Static Nature of π···π Interactions in Fused Benzene-Type Helicenes and Dimers, Elucidated with QTAIM Dual Functional Analysis

“…Helicenes are chiral; as a result, they are expected to have specific functionalities. Recently, helicenes have been widely applied in various fields [ 1 , 2 , 3 , 4 , 5 ], such as organic semiconductors [ 6 , 7 , 8 , 9 , 10 ], asymmetric catalysis [ 11 , 12 , 13 , 14 , 15 , 16 ], and molecular recognition [ 17 , 18 , 19 , 20 , 21 , 22 ], due to their diverse functionalities in materials. Many studies have also been reported on self-assembly phenomena at metal surfaces [ 23 , 24 , 25 , 26 ] caused by interactions with the π-orbitals of helicenes.…”

Synthesis, Characterization, and Thin-Film Transistor Response of Benzo[i]pentahelicene-3,6-dione

“…A handful of studies are available for other types of devices, such as organic light emitting diodes [ 37 , 38 , 39 , 40 , 41 , 42 , 43 , 44 , 45 , 46 , 47 , 48 , 49 , 50 , 51 , 52 , 53 , 54 , 55 , 56 ], organic solar cells [ 57 , 58 , 59 ], and hybrid DSSC [ 60 ] and perovskite solar cells [ 61 , 62 , 63 , 64 , 65 , 66 , 67 , 68 , 69 , 70 , 71 , 72 ].…”