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Product Code M2425A1-500mg
Price $213 ex. VAT

Self-Assembled Monolayer with Carbazole-based Phosphonic Acid

2PACz, Hole transport or extraction layer for highly efficient NFA-polymer solar cells and p-i-n perovskite solar cells, CAS No. 20999-38-6


2PACz, also known as (2-(9H-carbazol-9-yl)ethyl)phosphonic acid, consists of an electron rich carbazole body with an ethyl phosphonic acid anchoring group.

This material acts as a self-assembled monolayer (SAM) onto indium-tin-oxide (ITO) substrates in organic solar cells and perovskite solar cells. It replaces PEDOT:PSS as hole transport or extracting layer material. In between the ITO substrate and the active layer materials, 2PACz changes the work function of ITO while altering the morphology of the active layer materials.

In perovskite solar cells, 2PACz exhibits a well-suited energetic alignment and a significantly reduced non-radiative recombination at the contact/perovskite interface, outperforming those based on benchmark hole transport layer materials. This self-assembled monolayer has a better band alignment to the valence band of the perovskite absorber, compared to commonly used HTL PTAA.

The use of 2PACz has enabled almost lossless contacts, minimum interfacial recombination, and improved power conversion efficiency in single-junction and tandem solar cells. 2PACz causes spontaneous vertical phase separation of photoreactive layers, forming a vertical component distribution to improve carrier yield-mobility, and suppress the trap-assisted recombination and leaking current in indoor OPVs.

World-record high efficiency of 20.17% (19.79% certified, published on 21 March 2024) was achieved for organic polymer non-fullerene solar cells by engaging 2PACz as the self-assembled interlayer (SAI) to form a a thin layer of 2–6 nm, enabling a full coverage on the substrate (not a monolayer but few layers coverage) [1].

Serving as hole selective contact for organic solar cells and perovskite solar cells, 2PACz is an alternative to PEDOT:PSS with superior performance with the convenience of solution deposition at low concentration, i.e. 1 mM.

Solution Processing Procedure

Typical processing solvents: ethanol, methanol, THF, IPA, DMF
Typical concentration: 1 mM (0.275 mg/ml) or 1.0 mg/ml (1 mg 2PACz is dissolved in 1 ml ethanol)

Typical processing procedure: 100 uL of 2PACz solution is deposited onto the centre of the substrate surface and spin-coated for 30 s at the speed of 3000 rpm . After annealing for 10 min at 100 ℃.

General Information

CAS Number 20999-38-6
Chemical Formula C14H14NO3P
Molecular Weight 275.24 g/mol
Absorption* λmax 340 nm (on ITO glass)
Fluorescence λem (n.a.)
HOMO/LUMO HOMO = 5.6 eV, LUMO = 2.1 eV [2]
Synonyms (2-(9H-carbazol-9-yl)ethyl)phosphonic acid
Classification or Family Carbazole derivatives, Self-assembly Monolayers, Hole transport layer, Hole extraction layer, p-i-n Perovskite solar cells, Organic photovoltaics

Product Details

Purity > 98% (1H NMR)
Melting Point Tm = 231 ° C
Appearance Off-white powder/crystals

Chemical Structure

2pacz - 20999-38-6 - (2-(9H-carbazol-9-yl)ethyl)phosphonic acid chemical structure
2PACz - (2-(9H-carbazol-9-yl)ethyl)phosphonic acid chemical structure, 20999-38-6


MSDS Documentation

2pacz - 20999-38-6 - (2-(9H-carbazol-9-yl)ethyl)phosphonic acid2PACz MSDS Sheet

Literature and Reviews

  1. Self-Assembled Interlayer Enables High-Performance Organic Photovoltaics with Power Conversion Efficiency Exceeding 20%, S. Guan et al., Adv. Mater., 2400342 (2024); DOI: 10.1002/adma.202400342.
  2. Advantages and challenges of self-assembled monolayer as a hole-selective contact for perovskite solar cells, S. Wang et al., Mater. Futures. 2, 012105 (2023); DOI: 10.1088/2752-5724/acbb5a.
  3. Self-Assembled Monolayer Enables Hole Transport Layer-Free Organic Solar Cells with 18% Efficiency and Improved Operational Stability, Y. Lin et al., ACS Energy Lett. , 5 (9), 2935–2944 (2020); DOI: 10.1021/acsenergylett.0c01421.
  4. Record indoor performance of organic photovoltaics with long-term stability enabled by self-assembled monolayer-based interface management, T. Kim et al., Nano Energy, 112, 108429 (2023); DOI: 10.1016/j.nanoen.2023.108429.
  5. Evaporated Self-Assembled Monolayer Hole Transport Layers: Lossless Interfaces in p-i-n Perovskite Solar Cells, A. Farag et al., Adv. Energy Mater., 13 (8), 2203982 (2023); DOI: 10.1002/aenm.202203982.
  6. Fully Textured, Production-Line Compatible Monolithic Perovskite/Silicon Tandem Solar Cells Approaching 29% Efficiency, L. Mao et al., Adv. Mater., 34 (40), 2206193 (2022); DOI: 10.1002/adma.202206193.
  7. Monolithic All-Perovskite Tandem Solar Cells with Minimized Optical and Energetic Losses, K. Datta et al., Adv. Mater., 34 (11), 2110053 (2022); DOI: 10.1002/adma.202110053.
  8. Non-Fused Ring Acceptors Achieving over 15.6% Efficiency Organic Solar Cell by Long Exciton Diffusion Length of Alloy-Like Phase and Vertical Phase Separation Induced by Hole Transport Layer, D. Luo et al., Adv. Energy Mater., 13 (6), 2203402 (2023); DOI: 10.1002/aenm.202203402.

Licensed by Helmholtz-Zentrum Berlin für Materialien und Energie GmbH in Germany and Kaunas University of Technology in Lithuania.

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