Inkjet printing of NiO films and integration as hole transporting layers in polymer solar cells

Abstract

Stability concerns of organic solar cell devices have led to the development of alternative hole transporting layers such as NiO which lead to superior device life times over conventional Poly(3,4-ethylenedioxythiophene) Polystyrene sulfonate (PEDOT:PSS) buffered solar cells. From the printability of such devices, it is imperative to be able to print NiO layers in the organic solar cell devices with normal architecture which has so far remained unreported. In this manuscript, we report on the successful ink-jet printing of very thin NiO thin films with controlled thickness and morphology and their integration in organic solar cell devices. The parameters that were found to strongly affect the formation of a thin yet continuous NiO film were substrate surface treatment, drop spacing, and substrate temperature during printing. The effect of these parameters was investigated through detailed morphological characterization using optical and atomic force microscopy and the results suggested that one can achieve a transmittance of ~89% for a ~18 nm thin NiO film with uniform structure and morphology, fabricated using a drop spacing of 50 μm and a heat treatment temperature of 400 °C. The devices fabricated with printed NiO hole transporting layers exhibit power conversion efficiencies comparable to the devices with spin coated NiO films.

Nanocomposite of nickel oxide nanoparticles and polyethylene oxide as printable hole transport layer for organic solar cells

“…Notably, the results show that the inclusion of PEO is necessary to obtain the well performing of the NiO x HTLs, with an average PCE ¼ 2.37%. This performance is comparable to the ones obtained in literature with NiO x precursors (sol-gel method) that require a thermal treatment >200 C. 29 Our approach, thus, provides an excellent low-temperature alternative that enables inkjet printing of NiO x HTLs for solution-processed photovoltaics application.…”

“…25,26 Such sol-gel systems can be printed using inkjet, leading to injection layers which display performances in various organic and dyesensitized solar cells that are comparable to spin-coated systems. [27][28][29] In spite of these encouraging results, the high processing temperatures that are required to produce wellperforming layers are not compatible with exible plastic substrates and would be a drawback for the fabrication of costefficient devices by high-throughput printing or coating technologies. 30,31 In this work, we demonstrate a low temperature process ($100 C) for NiO x layers and their integration in organic solar cells by inkjet printing, via use of NiO x nanoparticles blended with high molecular weight polyethylene oxide (PEO) as a sacricial processing additive that do not require any high temperature treatment.…”

Microplasma-synthesized ultra-small NiO nanocrystals, a ubiquitous hole transport material

“…Also there are reports showing that non-stoichiometric NiO x nanoparticles can form an efficient hole transport layer at room temperature for high performance solar cells with different polymer or perovskite active layers. [23][24][25][26][27][28] Zhang et al 23 demonstrated a surfacenanostructured NiO x lm formed by a room-temperature solution process for achieving high performance exible perovskite solar cells with good stability and reproducibility. Irwin et al 24 showed that a thin (5-80 nm) layer of NiO as an anode layer can minimize the interfacial power losses and enhance the efficiency of polymer bulk-heterojunction solar cells.…”

P3HT-based visible-light organic photodetectors using PEI/PAA multilayers as a p-type buffer layer

“…The C 1 of the device using NiO x is slightly higher than that of the device using PEDOT:PSS because the holes transported from the active layer to the electrode are accumulated at the NiO x /P3HT interface due to the potential barrier created by NiO x having a deeper highest occupied molecular orbital (HOMO) (5.4 eV) than the HOMO of P3HT (5.0 eV). 42,43 As a result, weak band bending occurs in the downward direction at the NiO x /P3HT interface and the holes are transferred from the HOMO of P3HT to the electrode through the HOMO of NiO x . This process is illustrated in Fig.…”