Phenanthrene‐Fused‐Quinoxaline as a Key Building Block for Highly Efficient and Stable Sensitizers in Copper‐Electrolyte‐Based Dye‐Sensitized Solar Cells

Synthesis And Photovoltaic Performance of Carbazole (Donor) Based Photosensitizers in Dye-Sensitized Solar Cells (DSSC): A Review

Carbazoles are nitrogen-containing aromatic heterocycles, having widespread applications in the field of photovoltaics. Carbazole-based photosensitizers have tunable features for absorption on semi-conductor (tellurium dioxide or zinc oxide) layers to create sufficient push-pull force in the conversion of sunlight into electrical energy, thus presenting as promising heterocyclic donor candidates to be used in dye-sensitized solar cells. For the synthesis of these dyes, various structural designs are available, namely, D-A, D-π-A, D-D-π-A, D-A-π-A, A-π-D-π-A-π-A, and D2-π-A that all involve incorporating carbazole as a donor (D), along with spacer (π-extender) moieties, such as thiophene, phenol, ethynylene, nitromethane, azine, thiadiazole, or acetonitrile. Additionally, acceptors (A) employed in the designs include cyanoacrylic acids, carboxylic acids, malononitrile, rhodanine-3-acetic acid, 4-aminobenzoic acid, or 4-amino salicylic acid. This comprehensive review explores the synthesis and photovoltaic performances of numerous carbazole-based photosensitizers tailored for dye-sensitized solar cells, covering the period of 2019-2023.

Quinoxaline derivatives as attractive electron-transporting materials

This review article provides a comprehensive overview of recent advancements in electron transport materials derived from quinoxaline, along with their applications in various electronic devices. We focus on their utilization in organic solar cells (OSCs), dye-sensitized solar cells (DSSCs), organic field-effect transistors (OFETs), organic-light emitting diodes (OLEDs) and other organic electronic technologies. Notably, the potential of quinoxaline derivatives as non-fullerene acceptors in OSCs, auxiliary acceptors and bridging materials in DSSCs, and n-type semiconductors in transistor devices is discussed in detail. Additionally, their significance as thermally activated delayed fluorescence emitters and chromophores for OLEDs, sensors and electrochromic devices is explored. The review emphasizes the remarkable characteristics and versatility of quinoxaline derivatives in electron transport applications. Furthermore, ongoing research efforts aimed at enhancing their performance and addressing key challenges in various applications are presented.

Theoretical and experimental insights into the properties of donor–σ–acceptor type derivatives of quinoxaline and methanone containing different donor moieties

A strategy of fused electron accepting moieties was employed to synthesise a series of donor-substituted quinoxaline–methanone derivatives as red TADF emitters.

Stable Dye-Sensitized Solar Cells Based on Copper(II/I) Redox Mediators Bearing a Pentadentate Ligand

In recent years, copper redox mediators have attracted growing interest in dye-sensitized solar cells (DSCs). However, experiments revealed that ubiquitously used Lewis-base additives in the electrolytes coordinate to the Cu^II species, which restricts further enhancement of device performance and stability. We report the application of copper complexes endowed with diamine-tripyridine pentadentate ligands, [Cu(tpe)]^2+/+ (tpe=N-benzyl-N,N',N'-tris(pyridin-2-ylmethyl)ethylenediamine) and [Cu(tme)]^2+/+ (tme=N-benzyl-N,N',N'-tris(6-methylpyridin-2-ylmethyl)ethylenediamine), as redox mediators in DSCs. Experimental measurements demonstrate that the coordination environment of Cu(II) complexes with pentadentate ligands remains unchanged in the presence of TBP, which is in stark contrast to the state-of-the-art bipyridyl counterpart. DSCs based on [Cu(tme)]^2+/+ complexes exhibit an excellent long-term stability and maintain more than 90 % of the initial efficiency after 400 h under continuous illumination, which outperform the reference devices incorporating the bipyridyl counterpart (less than 80 %) under identical conditions.

A Coplanar π-Extended Quinoxaline Based Hole-Transporting Material Enabling over 21 % Efficiency for Dopant-Free Perovskite Solar Cells

Developing dopant-free hole transporting materials (HTMs) is of vital importance for addressing the notorious stability issue of perovskite solar cells (PSCs). However, efficient dopant-free HTMs are scarce. Herein, we improve the performance of dopant-free HTMs featuring with a quinoxaline core via rational π-extension. Upon incorporating rotatable or chemically fixed thienyl substitutes on the pyrazine ring, the resulting molecular HTMs TQ3 and TQ4 show completely different molecular arrangement as well as charge transporting capabilities. Comparing with TQ3, the coplanar π-extended quinoxaline based TQ4 endows enriched intermolecular interactions and stronger π-π stacking, thus achieving a higher hole mobility of 2.08×10^-4  cm²  V^-1  s^-1 . It also shows matched energy levels and high thermal stability for application in PSCs. Planar n-i-p structured PSCs employing dopant-free TQ4 as HTM exhibits power conversion efficiency (PCE) over 21 % with excellent long-term stability.