Interface Behaviour and Work Function Modification of Self-Assembled Monolayers on Sn-Doped In2O3

Hubmann, Andreas H.; Dietz, Dominik; Brötz, Joachim; Klein, Andreas

doi:10.3390/surfaces2020019

Cited by 3 publications

(3 citation statements)

References 60 publications

(103 reference statements)

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“… 2 However, the work function of SAM-functionalized ITO has also been found to be sensitive to the UV–O 3 treatment time. 9 A report using 2PACz SAM also demonstrated that the performance of organic solar cells depended on the duration of O 2 -plasma treatment preceding SAM deposition. 10 Since the hydroxyl group concentration on any surface is a key element for promoting SAM formation via covalent bonds, 11 , 12 hydroxyl group rich NiO processed by atomic layer deposition (ALD) is expected to promote controlled and homogeneous SAM formation.…”

Section: Introductionmentioning

confidence: 98%

“…Al-Ashouri et al reported that UV–O 3 was essential for surface activation of ITO for SAM formation in perovskite solar cells . However, the work function of SAM-functionalized ITO has also been found to be sensitive to the UV–O 3 treatment time . A report using 2PACz SAM also demonstrated that the performance of organic solar cells depended on the duration of O 2 -plasma treatment preceding SAM deposition .…”

Section: Introductionmentioning

confidence: 99%

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Enhanced Self-Assembled Monolayer Surface Coverage by ALD NiO in p-i-n Perovskite Solar Cells

Phung

Verheijen

Todinova

et al. 2021

ACS Appl. Mater. Interfaces

129

118

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Metal halide perovskites have attracted tremendous attention due to their excellent electronic properties. Recent advancements in device performance and stability of perovskite solar cells (PSCs) have been achieved with the application of self-assembled monolayers (SAMs), serving as stand-alone hole transport layers in the p-i-n architecture. Specifically, phosphonic acid SAMs, directly functionalizing indium–tin oxide (ITO), are presently adopted for highly efficient devices. Despite their successes, so far, little is known about the surface coverage of SAMs on ITO used in PSCs application, which can affect the device performance, as non-covered areas can result in shunting or low open-circuit voltage. In this study, we investigate the surface coverage of SAMs on ITO and observe that the SAM of MeO-2PACz ([2-(3,6-dimethoxy-9H-carbazol-9-yl)ethyl]phosphonic acid) inhomogeneously covers the ITO substrate. Instead, when adopting an intermediate layer of NiO between ITO and the SAM, the homogeneity, and hence the surface coverage of the SAM, improve. In this work, NiO is processed by plasma-assisted atomic layer deposition (ALD) with Ni(MeCp) 2 as the precursor and O 2 plasma as the co-reactant. Specifically, the presence of ALD NiO leads to a homogeneous distribution of SAM molecules on the metal oxide area, accompanied by a high shunt resistance in the devices with respect to those with SAM directly processed on ITO. At the same time, the SAM is key to the improvement of the open-circuit voltage of NiO + MeO-2PACz devices compared to those with NiO alone. Thus, the combination of NiO and SAM results in a narrower distribution of device performance reaching a more than 20% efficient champion device. The enhancement of SAM coverage in the presence of NiO is corroborated by several characterization techniques including advanced imaging by transmission electron microscopy (TEM), elemental composition quantification by Rutherford backscattering spectrometry (RBS), and conductive atomic force microscopy (c-AFM) mapping. We believe this finding will further promote the usage of phosphonic acid based SAM molecules in perovskite PV.

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Section: Introductionmentioning

confidence: 98%

Section: Introductionmentioning

confidence: 99%

Enhanced Self-Assembled Monolayer Surface Coverage by ALD NiO in p-i-n Perovskite Solar Cells

Phung

Verheijen

Todinova

et al. 2021

ACS Appl. Mater. Interfaces

129

118

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show abstract

“… 52 Another theory that may elucidate the phenomenon of crystalline orientation’s influence on local WF variation is the surface polarity concept, introduced by Tasker. 53 While the initial observations were for In 2 O 3 , 52 , 54 , 55 this concept can be extended to ITO. In detail, the (111) plane is a Tasker II type of surface without surface dipole perpendicular to the surface normal.…”

Section: Methodsmentioning

confidence: 99%

Impact of the TCO Microstructure on the Electronic Properties of Carbazole-Based Self-Assembled Monolayers

Kralj,

Dally,

Bampoulis

et al. 2023

ACS Materials Lett.

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Carbazole-based self-assembled monolayers (PACz-SAMs), anchored via their phosphonic acid group on a transparent conductive oxide (TCO), have demonstrated excellent performance as hole-selective layers in perovskite/ silicon tandem solar cells. Yet, whereas different PACz-SAMs have been explored, the role of the TCO, and specifically its microstructure, on the hole transport properties of the TCO/ PACz-SAMs stack has been largely overlooked. Here, we demonstrate that the TCO microstructure directly impacts the work function (WF) shift after SAM anchoring and is responsible for WF variations at the micro/nanoscale. Specifically, we studied Sn-doped In 2 O 3 (ITO) substrates with amorphous and polycrystalline (featuring either nanoscale-or microscale-sized grains) microstructures before and after 2PACz-SAMs and NiO x /2PACz-SAMs anchoring. With this, we established a direct correlation between the ITO crystal grain orientation and 2PACz-SAMs local potential distribution, i.e., the WF. Importantly, these variations vanish for amorphous oxides (either in the form of amorphous ITO or when adding an amorphous NiO x buffer layer), where a homogeneous surface potential distribution is found. These findings highlight the importance of TCO microstructure tuning, to enable both high mobility and broadband transparent electrodes while ensuring uniform WF distribution upon application of hole transport SAMs, both critical for enhanced device performance.

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Artificial optoelectronic synaptic characteristics of Bi2FeMnO6 ferroelectric memristor for neuromorphic computing

Zhong¹,

Tang²,

Liu³

et al. 2022

Materials & Design

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Interface Behaviour and Work Function Modification of Self-Assembled Monolayers on Sn-Doped In2O3

Cited by 3 publications

References 60 publications

Enhanced Self-Assembled Monolayer Surface Coverage by ALD NiO in p-i-n Perovskite Solar Cells

Enhanced Self-Assembled Monolayer Surface Coverage by ALD NiO in p-i-n Perovskite Solar Cells

Impact of the TCO Microstructure on the Electronic Properties of Carbazole-Based Self-Assembled Monolayers

Artificial optoelectronic synaptic characteristics of Bi2FeMnO6 ferroelectric memristor for neuromorphic computing

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