A Triple Axial Chirality, Racemic Molecular Semiconductor Based on Thiahelicene and Ethylenedioxythiophene for Perovskite Solar Cells: Microscopic Insights on Performance Enhancement

Abstract

For the low‐cost fabrication of large‐area, durable perovskite solar cells, it is of pivotal importance to engineer organic semiconducting films with a combined property of matched energy level, sufficiently large conductivity, high glass transition temperature, and excellent solution processability. Toward this goal, herein an in silico tailored molecular semiconductor (T5HE‐OMeTPA) with triple axial chirality, by joint use of thia[5]helicene and ethylenedioxythiophene, is reported. T5HE‐OMeTPA with a reduced reorganization energy of hole transfer can be exploited as the hole transport layer for perovskite solar cells with 21% efficiency, which also display excellent long‐term stability at 60 °C. The doped, sufficiently conductive T5HE‐OMeTPA composite with a glass transition temperature of 121 °C not only exhibits persistent film morphology under thermal stress, but also surprisingly damps the motion of diffusive components of perovskite for a better control of the degradation of photoactive layer. The translational motion of both ions and molecules is intrinsically associated with the glass transition of a doped molecular semiconductor composite, which is in stark contrast to the microscopic fashion for the glass transition of an undoped molecular semiconductor, that is, thermally activated rotation of diphenylamine.

A Helicene-Based Molecular Semiconductor Enables 85 °C Stable Perovskite Solar Cells

“…Nonplanar conjugated polycycles are drawing ever-increasing attention in recent years, with a view to the peculiar topology, photophysics, charge transport, and solution processability . Helicenes characteristic of ortho-fused polycyclic aromatics are naturally tethered with chirality owing to the steric repulsion of terminal rings. , Although helicenes with various fantastic topology structures have been designed and synthesized, the use of helicenes for emerging electronic devices has not yet achieved some disruptive breakthroughs. − In this context, some archetype helicenes such as aza[5]­helicene, , oxa[5]­helicene, and thia[5]­helicene (T5H) , have been recently used as the π-linkers of donor−π–donor (D−π–D)-type HTMs for PSCs, in conjunction with the electron donor of bis­(4-methoxyphenyl)­amine (OMeDPA). However, the conductivities of these molecular semiconductors are not sufficiently high for direct applications in PSCs without doping, and the doped semiconductor composites actually present a Τ g of less than 70 °C, failing in the fabrication of 85 °C durable devices.…”

“…33,34 Although helicenes with various fantastic topology structures have been designed and synthesized, the use of helicenes for emerging electronic devices has not yet achieved some disruptive breakthroughs. 35−40 In this context, some archetype helicenes such as aza [5]helicene, 41,42 oxa [5]helicene, 43 and thia [5]helicene (T5H) 44,45 have been recently used as the π-linkers of donor−π−donor (D−π−D)-type HTMs for PSCs, in conjunction with the electron donor of bis(4-methoxyphenyl)amine (OMeDPA). However, the conductivities of these molecular semiconductors are not sufficiently high for direct applications in PSCs without doping, and the doped semiconductor composites actually present a Τ g of less than 70 °C, failing in the fabrication of 85 °C durable devices.…”

Simple Yet Efficient: Arylamine‐Terminated Carbazole Donors for Organic Hole Transporting Materials

“…PSCs based on M142 (HOMO = −5.07 eV) present a higher V oc than M144, although the later exhibits a deeper HOMO (−5.14 eV). Therefore, the interfacial charge recombination is essential for V oc of the studied devices, [ 62 ] whereas HOMO is not the key factor to influence the V oc of M142. It is known that the interfacial charge recombination depended on the film morphology and hole mobility of HTM layer.…”

Structurally Nontraditional Benzo[c]cinnoline‐Based Electron‐Transporting Materials with 3D Molecular Interaction Architecture

“…Thus, it is highly desirable to improve the T g while maintain a fast μ e for BPhen in both academic and industry communities. In general, T g could be improved by increasing molecular weight or enhancing intermolecular interactions [6] . For example, 1,4‐bis(2‐phenyl‐1,10‐phenanthrolin‐4‐yl)benzene ( p ‐bPPhenB ) with two Phen moieties exhibits a higher T g value (123.9 °C) due to a higher molecular weight [5b] .…”