High-Performance Silver Window Electrodes for Top-Illuminated Organic Photovoltaics Using an Organo-molybdenum Oxide Bronze Interlayer

Abstract

We report an organo-molybdenumn oxide bronze that enables the fabrication of high-performance silver window electrodes for top-illuminated solution processed organic photovoltaics without complicating the process of device fabrication. This hybrid material combines the function of wide-band-gap interlayer for efficient hole extraction with the role of metal electrode seed layer, enabling the fabrication of highly transparent, low-sheet-resistance silver window electrodes. Additionally it is also processed from ethanol, which ensures orthogonality with a large range of solution processed organic semiconductors. The key organic component is the low cost small molecule 3-mercaptopropionic acid, which (i) promotes metal film formation and imparts robustness at low metal thickness, (ii) reduces the contact resistance at the Ag/molybdenumn oxide bronze interface, (iii) and greatly improves the film forming properties. Silver electrodes with a thickness of 8 nm deposited by simple vacuum evaporation onto this hybrid interlayer have a sheet resistance as low as 9.7 Ohms per square and mean transparency ∼80% over the wavelength range 400-900 nm without the aid of an antireflecting layer, which makes them well-matched to the needs of organic photovoltaics and applicable to perovskite photovoltaics. The application of this hybrid material is demonstrated in two types of top-illuminated organic photovoltaic devices.

Stabilizing Silver Window Electrodes for Organic Photovoltaics Using a Mercaptosilane Monolayer

“…After the second MPTMS vapor deposition both Si and S are clearly present in the XPS spectrum taken from the surface of the 9 nm Ag film (Figure 2). In the S 2p binding energy region in Figure 2 there are two doublets consistent with two distinct chemical environments for the S. 20 Based on the intensity and binding energies of each pair, sulfur exists primarily as a thiolate covalently bound to Ag, and the minor component is free thiol or disulfide. Given that 8% of the surface comprises polymerized aggregation of MPTMS with a height equivalent to several MPTMS molecules, it is plausible that the free thiol is associated primarily with these localized mounds.…”

“…After the second MPTMS vapor deposition both Si and S are clearly present in the XPS spectrum taken from the surface of the 9 nm Ag film (Figure ). In the S 2p binding energy region in Figure there are two doublets consistent with two distinct chemical environments for the S . Based on the intensity and binding energies of each pair, sulfur exists primarily as a thiolate covalently bound to Ag, and the minor component is free thiol or disulfide.…”

Printed Solar Cells and Energy Storage Devices on Paper Substrates

“…nanotubes, 2D materials such as graphene, multilayer stacks of thin metal/dielectrics and a combination of these. [37,[91][92][93][94][95][96][97] The back electrode usually consists of a thin metallic film i.e. gold (Au), silver (Ag), aluminium (Al) or Platinum (Pt).…”

Emerging Novel Metal Electrodes for Photovoltaic Applications

“…Recently, the strategy of molecule treatment on the substrate or the metal oxide layer, such as (3-mercaptopropyl) trimethoxysilane (MPTMS), oxygen plasma treated ormoclear, 11-mercapto-undecanoic acid, polyethyleneimine (PEI), polyallylamine, poly(N-vinylcarbazole), and bathocuproine (BCP) can greatly improve the wetting of metal film on the substrate, by taking advantage of the strong bonding between metal atoms and the functional groups of thiol or amine in the molecules to minimize the coalesce of metal atoms into clusters. [339][340][341][342][343][344][345][346][347][348] Sub-10 nanometer metal film with smooth and continuous surface can be achieved through this approach, which enables the high transparency and conductivity of the electrode. In addition, the work function of the electrode can also be altered due to the metal film modification by the dipole layer of small molecules, which is advantageous to the performance of optoelectronic devices.…”

“…The previous strategy of coating a metal oxide layer on substrate can help the formation of continuous and smooth ultrathin metal film allowing the partial transmission of visible light. Recently, the strategy of molecule treatment on the substrate or the metal oxide layer, such as (3‐mercaptopropyl) trimethoxysilane (MPTMS), oxygen plasma treated ormoclear, 11‐mercapto‐undecanoic acid, polyethyleneimine (PEI), polyallylamine, poly( N ‐vinylcarbazole), and bathocuproine (BCP) can greatly improve the wetting of metal film on the substrate, by taking advantage of the strong bonding between metal atoms and the functional groups of thiol or amine in the molecules to minimize the coalesce of metal atoms into clusters . Sub‐10 nanometer metal film with smooth and continuous surface can be achieved through this approach, which enables the high transparency and conductivity of the electrode.…”