Donor‐π‐Acceptor N‐Methyl‐4,5‐Diazacarbazole Based Ultra‐High Performance Organic Solar Cells: A Density Functional Theory Study

Abstract

The organic conjugated semiconductors have attracted the immense attention of scientists due to their pivotal role during charge transfer processes in organic solar cells (OSCs), [1] light-emitting diodes (LEDs), [2] and organic fields transistors (OFETs). [3] As compared to the commercially used inorganic materials, organic semiconductors are superior in their abundance, easy fabrication, low cost, flexibility, and extended π-conjugation. [4,5] In photovoltaic and solar cell devices suitable electronic properties i.e., bandgaps and charge transfer are key parameters governing their performance. [6] Therefore, the research to explore the structure-property relationship of organic semiconductors is immensely important. [7,8] Many research studies have been published, illustrating the modifications of organic materials to decrease their gaps and increase charge mobility. [9,10] It is illustrated that the incorporation of electron-deficient (acceptor) in an electron-rich donor unit leads to the fabrication or development of suitable organic photovoltaic materials with excellent performance. [11][12][13] This type of tailoring is not only effective in narrowing the HOMO-LUMO bandgaps but also enhances intramolecular charge transfer from the electron-rich donor part to the electron-deficient acceptor unit, which can be facilitated through the highly conjugated connector (bridge). [14] Thiophene has unique advantages over other conjugated bridges including benzene and furan because of its higher ability to reduce charge recombination and higher optical activity shown by Palomares et al., [15] and Kumar et al., [16] respectively. In the context of materials discovery, the search for suitable or appropriate pairs of donor and acceptor units became the most crucial step for better control of PV devices. [17,18] This strategy allows for the rational design of donor (D)-acceptor (A) based organic molecules having high activity in the UV-visible region of the electromagnetic spectrum. [19] In this regard, both fullerenes [20] and non-fullerenes [21] materials have been tested. However, the non-fullerene-based materials are superior to fullerene systems in terms of easy handling, synthesis, and purification, high absorption in the solar spectrum, ease in tuning the energy levels, etc. [21,22] In recent years, non-fullerene-based acceptor molecules

Exploration of the synergistic effect of chrysene-based core and benzothiophene acceptors on photovoltaic properties of organic solar cells

“…MEPs are assessed to elucidate the quantitative representation of intermolecular charge distribution between the donor and acceptor regions of a molecular system 47 . MEP surfaces resemble a cloud with three main colors, each indicating a specific strength of the molecule's electrostatic potential.…”

Theoretical Insights into the Structural and Optical Properties of D−π–A-based Cyanostilbene Systems of α and β Variants

“…Cyanostilbene appended donor–π–acceptor (D−π–A) type systems, where the cyano moiety acts as the acceptor (A), are the more straightforward model for a comprehensive understanding of the effect of positional isomerism of α and β analogs of cyanostilbene because it allows flexibility in molecular design by changing either conjugating moiety (π) or donor unit (D) systematically. ,− Such systems are capable of fabricating excellent hole and electron transport facilities and executing push–pull effects, allowing electron transfer from the donor to the acceptor through the conjugated π-units. − Furthermore, D−π–A architecture having functionalized acrylonitrile compounds offers better nonlinear optical (NLO) performance. − For example, Singh and co-workers recently synthesized a series of cyanostilbene-based D−π–A systems containing the 9,9-dimethyl-9 H -fluoren-2-amine type of chromophores and observed a significant enhancement in the first hyperpolarizability and related intrinsic hyperpolarizability by modulating the π-conjugation pathways . In a continued work, the same group compared the first hyperpolarizabilities by extending the π-conjugation of D−π–A systems and found that lengthening of π-conjugation beyond a certain limit hardly improves the NLO response.…”