18.4 % Organic Solar Cells Using a High Ionization Energy Self‐Assembled Monolayer as Hole‐Extraction Interlayer

Abstract

Self-assembled monolayers (SAMs) based on Br-2PACz ([2-(3,6dibromo-9H-carbazol-9-yl)ethyl]phosphonic acid) 2PACz ethyl]phosphonic acid) and ethyl]phosphonic acid) molecules were investigated as hole-extracting interlayers in organic photovoltaics (OPVs). The highest occupied molecular orbital (HOMO) energies of these SAMs were measured at À 6.01 and À 5.30 eV for Br-2PACz and MeO-2PACz, respectively, and found to induce significant changes in the work function (WF) of indium-tin-oxide (ITO) electrodes upon chemical functionalization. OPV cells based on PM6 (poly [(2,6-(4,8-bis(5-(2-ethylhexyl-3- ([6,6]-phenyl-C71-bu-tyric acid methyl ester) using ITO/Br-2PACz anodes exhibited a maximum power conversion efficiency (PCE) of 18.4 %, outperforming devices with ITO/MeO-2PACz (14.5 %) and ITO/poly (3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PE-DOT : PSS) (17.5 %). The higher PCE was found to originate from the much higher WF of ITO/Br-2PACz (À 5.81 eV) compared to ITO/MeO-2PACz (4.58 eV) and ITO/PEDOT : PSS (4.9 eV), resulting in lower interface resistance, improved hole transport/extraction, lower trap-assisted recombination, and longer carrier lifetimes. Importantly, the ITO/Br-2PACz electrode was chemically stable, and after removal of the SAM it could be recycled and reused to construct fresh OPVs with equally impressive performance.

Aminonaphthalimide‐Based Molecular Cathode Interlayers for As‐Cast Organic Solar Cells

“…As we all know, high degree of crystalline order, good thermal stability and weak dependence on the thicknesses of interface are of significance for cathode interfacial materials to prepare efficient industrial OSCs. [33][34][35][36] Thus, it is highly desirable to develop a high quality cathode interlayer with low processing cost and simple synthesis route, enabling the potential commercialization of OSCs. [37] Herein, we developed three low-cost and simple imidebased molecules with different amine side-chains, namely Ndimethylaminopropyl-4-bromo-1,8-naphthalimide (NA), Ndimethylaminopropyl-4-dimethylaminopropylamino-1,8-naphthalimide (NAA), and N-dimethylaminopropyl-4-aminoethylamino-1,8-naphthalimide (NEA), used as cathode interlayers in OSCs (Scheme 1 and Figure 1a).…”

Tuning the antiaromatic character and charge transport of pentalene-based antiaromatic compounds by substitution

“…Aromaticity is a fundamentally important and intriguing property of numerous organic chemical structures and has stimulated a myriad of experimental and theoretical investigations. 1–3 Since Hückel first codified the (4 n + 2) π-electron rule for monocyclic rings as the guideline for aromaticity, 4 additional aromatic mono/oligocyclic rings have been reported 5–7 and investigated in research fields as diverse as materials science, 8–10 photonics, 11–13 agriculture, pharmaceuticals, 14 and biomedicine. 15 Antiaromaticity, where (4 n ) π-electrons are present in a conjugated cyclic structure, as the inverse concept of aromaticity, was first proposed by Breslow in 1967.…”

Eliminating the Detrimental Effect of Secondary Doping on PEDOT : PSS Hole Transporting Material Performance

“…[5][6][7] Apart from the development of acceptors, interface engineering upon electrodes, that is, developing hole/electron transporting materials (HTMs/ETMs), is also a most effective strategy to further enhance the performance of OSCs to a new level. [16][17][18][19][20][21][22][23][24][25][26][27] As for ETM development, multiple types of materials including metal oxides, small-molecule organic compounds, and nonconjugated/conjugated polymers endowed high performance for OSCs. [28][29][30] In sharp contrast, the development of HTMs is comparatively lagging behind.…”