Transfer-printing of active layers to achieve high quality interfaces in sequentially deposited multilayer inverted polymer solar cells fabricated in air

Abstract

Polymer solar cells (PSCs) are greatly influenced by both the vertical concentration gradient in the active layer and the quality of the various interfaces. To achieve vertical concentration gradients in inverted PSCs, a sequential deposition approach is necessary. However, a direct approach to sequential deposition by spin-coating results in partial dissolution of the underlying layers which decreases the control over the process and results in not well-defined interfaces. Here, we demonstrate that by using a transfer-printing process based on polydimethylsiloxane (PDMS) stamps we can obtain increased control over the thickness of the various layers while at the same time increasing the quality of the interfaces and the overall concentration gradient within the active layer of PSCs prepared in air. To optimize the process and understand the influence of various interlayers, our approach is based on surface free energy, spreading parameters and work of adhesion calculations. The key parameter presented here is the insertion of high quality hole transporting and electron transporting layers, respectively above and underneath the active layer of the inverted structure PSC which not only facilitates the transfer process but also induces the adequate vertical concentration gradient in the device to facilitate charge extraction. The resulting non-encapsulated devices (active layer prepared in air) demonstrate over 40% increase in power conversion efficiency with respect to the reference spin-coated inverted PSCs.

Strongly Iridescent Hybrid Photonic Sensors Based on Self-Assembled Nanoparticles for Hazardous Solvent Detection

“…As demonstrated by the photographs in Figure 1 , surface plasma treatment of the PDMS substrate is an essential step for ensuring that PS nanoparticles can be deposited from aqueous dispersions onto these high surface energy elastomeric substrates. Surface plasma treatment is a well-known technique that is often applied to improving the wetting properties of aqueous solutions onto hydrophobic layers such as poly(3,4-ethylenedioxythiophene) polystyrene sulfonate or PDMS [ 16 , 35 , 36 ].…”

All solution-processed micro-structured flexible electrodes for low-cost light-emitting pressure sensors fabrication

“…While direct deposition of the AgNWs suspension in isopropanol (IPA) does not result in homogeneously covered PDMS surfaces, depositing dense AgNWs networks on a PEDOT:PSS layer either by spin-coating or dip-coating has been previously demonstrated 17 , 18 . Furthermore, in our recent study, we used solvent additives in the PEDOT:PSS suspension and pre-deposition plasma treatment of the PDMS surface to produce PDMS substrates homogeneously covered with PEDOT:PSS 19 . We compared the performances of PDMS-based flexible electrodes by measuring their resistance at various pressures in devices containing an indium thin oxide (ITO) counter-electrode (Figure S1 , Supplementary Information).…”

Fabrication Processes to Generate Concentration Gradients in Polymer Solar Cell Active Layers

“…While lamination itself only allows for the formation of bilayer active layers, the use of micro-contact-printing or transfer-printing consists of alternative dry-transfer processes to generate multilayer active layers without any mixing between two sequentially deposited layers [72,73,74,75]. The two main issues for efficient transfer-printing are to deposit high quality films from chlorinated solvents on the substrates used as stamps and be able to entirely transfer the films from the stamp to the device substrate.…”

“…Adapted from [74,75], with permission from © 2009 Royal Society of Chemistry and © 2016 Taylor & Francis.…”