Leverage of Pyridine Isomer on Phenothiazine Core: Organic Semiconductors as Selective Layers in Perovskite Solar Cells

Abstract

To drive the development of perovskite solar cells (PSCs), hole-transporting materials are imperative. In this context, pyridine derivatives are being probed as small molecules-based hole-transporting materials due to their Lewis base and electron-deficient unit. Herein, we focused our investigation on pyridine isomer molecules 4,4′-(10-(pyridin- x -yl)-10H-phenothiazine-3,7-diyl)­bis­(N,N-bis­(4-methoxyphenyl)­aniline) ( x = 2, 3, or 4), in which the pyridine nitrogen heteroatom is located at the 2, 3, and 4 positions, named as 2PyPTPDAn, 3PyPTPDAn, and 4PyPTPDAn, respectively. We decipher the structure–properties–device performance relationship impacted by the different N-atom positions in pyridine. In the case of 3PyPTPDAn, the partial orbital overlap between highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) favors the generation of neutral excitons and hole transport, as well as improves the film-formation ability, and this induces efficient hole extraction as compared to their 2,4 analogues. The solar cells fabricated with 3PyPTPDAn gave on-par photovoltaic performance as that of typical Spiro-OMeTAD, and higher performance than those of 2PyPTPDAn and 4PyPTPDAn. The hydrophobicity and homogeneous film properties of 3PyPTPDAn add merits to the stability. This work emphasizes the guidelines to develop small molecules for organic solar cells, organic light-emitting diodes, and thermally activated delayed fluorescence.

Synthesis of dimethyl‐ and diphenylsilane‐based oligo(azine)s: Thermal, optical, electronic, and morphological properties

“…These materials have been extensively studied as advanced functional materials in the fields of photovoltaic, organic electronics, and sensing devices 67,68 . In this sense, the hydrophobicity shown by PAZ‐4 could be the start‐point for the design of new architectures based on oligo/poly(azine)s that allows the preparation of moisture stable thin‐film nano/microstructures with high potential in optoelectronic applications 67,69,70 …”

“…67,68 In this sense, the hydrophobicity shown by PAZ-4 could be the start-point for the design of new architectures based on oligo/poly(azine)s that allows the preparation of moisture stable thin-film nano/microstructures with high potential in optoelectronic applications. 67,69,70 The surface free energy (SFE) of PAZ-4 thin-films was analyzed according to the Owens-Wendt approach using its dispersive (nonpolar) and non-dispersive (polar) components (Figure 10a). 71 For this, surface tension values of water (total = 72.8 dyne/cm, dispersive = 21.8 dyne/cm and polar = 51 dyne/cm), glycerol (total = 64.0 dyne/cm, dispersive = 34.0 dyne/cm and polar = 30 dyne/cm), and diiodomethane (total = 50.8 dyne/cm, dispersive = 50.8 dyne/cm and polar = 0 dyne/cm) were considered.…”

Thia[5]helicene-Based D−π–A-type Molecular Semiconductors for Stable and Efficient Perovskite Solar Cells: A Theoretical Study

“…Besides developing new helicene-type π-linkers, rational tailoring of the molecular architecture, including D−π–A- (or D–A), − D−π–D-, ,, D–A–D-, ,− and D–A−π–A–D-type scaffolds, is an effective approach to enhance the performance of HTMs and to passivate the surface trap states of the perovskite. In contrast to traditional planar-type and spiro-type HTMs, the HTMs with the D–A-type architecture usually exhibit a variety of fascinating properties, such as the tunable energy levels, easy purification, effortless charge transport, and stable electron-rich arylamine system. , Particularly, a low-cost and eco-friendly D–A-type molecule MPA-BT-CA was reported by Guo et al through structural engineering with cyanoacrylic acid .…”

“…As one of the most promising alternatives to traditional silicon-based photovoltaic technology, organic–inorganic halide perovskite solar cells (PSCs) have attracted great research interest in the past decade due to the rapidly increased cell efficiencies and low-cost solution processing. − Currently, the PSCs have three typical device architectures, including the mesoporous structure, planar n-i-p structures, and p–i–n structures, and in all the state-of-the-art PSCs, hole-transporting materials (HTMs) play a very important role in promoting the dissociation of photogenerated excitons and the following hole transport. − Up to now, many efforts have been devoted to improve the property of HTMs by regulating the molecular skeleton and chemical composition. − Very recently, a series of helicene-type molecular semiconductors with curved π-surfaces have been developed as high-efficient HTMs to obtain the durable and cost-effective PSCs. − …”

Molecular Tailoring of Pyridine Core-Based Hole Selective Layer for Lead Free Double Perovskite Solar Cells Fabrication

“…The pyridine can be served as an electron-deficient and passivation function unit to create new HSLs . Pyridine-based HSLs and associated synthesis methodologies have been reported. , We put forward the linking topology of the pyridine core and common arms, as well as the N -position effects on pyridine-based HSLs. , …”