Contact resistance measurement - observations on technique and test parameters

Cl, Br, or I) where a monovalent molecular cation and divalent metal cation are occupied in the A-site and the B-site, respectively to active layers in various ways. [3] Thanks to their defect tolerance properties, many researchers have tried to control charge transport behaviors by minimizing defects that possibly exist in grain boundaries (GBs), interfaces, and structural imperfections. [4][5][6][7][8] In early research, single-crystal methyl-ammonium lead iodide (MAPbI 3 ) TFTs were reported whose maximum hole mobility (μ h ) was 4.7 cm 2 V −1 s −1 with bottom-gate bottom-contact (BGBC) configuration by Yu et al. [7] Recently, Zhu et al. reported 2D phenethylammonium tin iodide ((PEA) 2 SnI 4 ) TFTs with the methods of enlarging grain sizes by mixing the Lewis-based solvents and passivating iodide vacancies by oxygen treatment. [8] Comprehensively, these trials were based on optimizing morphologies of the films to overcome the Schottky barrier which is detrimental to the injection in the channel layers during the switching operation. Despite their feasible controllability, they still have unresolved problems in adjusting TFTs due to weak charge conduction, environmental instabilities, and gate-screening effect from ion migration. [9][10][11] Here, the defect-controlled inorganic halide perovskites (IHPs) were investigated. IHPs consisting of the extensive inorganic framework are considered to be alternative semiconducting materials, allowing TFTs to be operated for a longterm period and better conduction. [12,13] Among them, we chose cesium lead iodide (CsPbI 3 ) that has high intrinsic carrier mobility and diffusion length. [14] Even at the experimental value of the carrier mobility of the cubic (α)-CsPbI 3 film through a terahertz spectroscopy method, a charge carrier mobility of CsPbI 3 is above 30 cm 2 V −1 s −1 . [15] This value is higher than that of MAPbI 3 , MAPbI 3-x Cl x , FASnI 3 , FAPbBr 3 , and PEASnI 4, considering that the carrier mobility measurement method is the same. [16] Furthermore, extrinsic point defects can be formed by adding various additives, which can further improve the carrier mobility of the conventional α-CsPbI 3 . This electrically promising potential of α-CsPbI 3 is the main reason why we choose the active layer in TFT.However, high hole-doped HPs can be disadvantageous to TFT devices due to the difficulty to inhibit an overabundance of the hole carriers even in the off-state operation. [17] This can So far, it has been difficult to fabricate thin-film field-effect transistors (TFTs) based on inorganic halide perovskites (IHPs) due to their phase-instability and uncontrollable trap density. Here, the bottom-gate bottom-contact structured p-type TFTs are presented using the optimized IHP in the active layer. The stable cubic-CsPbI 3 phase is successfully synthesized by doping bismuth iodide and reduced defect densities by adding potassium bromide. The IHP TFTs based on the tailored cubic-CsPbI 3 show high hole mobility of ≈10 cm 2 V −1 s −1 , an on-off current ratio of 10 3 , a...

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“…With the measured R T (Figure 3c), R c according to the type of IHP can be calculated by Equation (2). [31] =…”

Section: Device Performancementioning

confidence: 99%

High Hole Mobility Inorganic Halide Perovskite Field‐Effect Transistors with Enhanced Phase Stability and Interfacial Defect Tolerance

Lee

Han

Lee

et al. 2021

Adv Elect Materials

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Section: Nanoprobing Strategy For Contact Resistance Measurementmentioning

confidence: 99%

“…To experimentally quantify the nanoprobing contact resistance, the transmission-line method (TLM) was employed [26]. The TLM is a rapid, accurate, and cost-effective technique for contact resistance measurement [26], and requires simpler testing structures than the cross-bridge Kelvin resistor structures [27]. It assumes linear dependence of the measured resistance (between the two probes) on the probe spacing (which is true for our Si nanowires with uniform surface conductivity), and involves multiple resistance measurements (at different probe spacings) from which the contact resistance can be extracted [26].…”

Section: Nanoprobing Strategy For Contact Resistance Measurementmentioning

confidence: 99%

“…This consistent landing operation ensures a relatively consistent level of contact force. In addition, it has been shown previously that unequally spaced contact points in the TLM provide more accurate measurement results [26], and this is the reason why the four contact points for a single nanowire (figure 6) were randomly selected in our experiments. Also note that the reason why we move the 'mobileelectrode' nanoprobe from the initial rightmost contact location towards the other probe (arrow directions in figure 6) is to ensure we always probe on intact portions of the nanowire and thus avoid the effect of probing-induced sample damage on the measurement data.…”

Section: R Wmentioning

confidence: 99%

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Investigating the impact of SEM chamber conditions and imaging parameters on contact resistance ofin situnanoprobing

Qu¹,

Lee²,

Hilke³

et al. 2017

Nanotechnology

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In this paper, we investigate the impact of vacuum chamber conditions (cleanliness level and vacuum pressure) and imaging parameters (magnification and acceleration voltage) of scanning electron microscopy (SEM) on the contact resistance of two-point in situ nanoprobing of nanomaterials. Using two typical types of conductive nanoprobe, two-point nanoprobing is performed on silicon nanowires, during which changing trends of the nanoprobing contact resistance with the SEM chamber conditions and imaging parameters are quantified. The mechanisms underlying the experimental observations are also explained. Through systematically adjusting the experimental parameters, the probe-sample contact resistance is significantly reduced from the mega-ohm level to the kilo-ohm level. The experimental results can serve as a guideline to evaluate electrical contacts of nanoprobing and instruct how to reduce the contact resistance in SEM-based, two-point nanoprobing.

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“…Bosco studied the fatigue of solder bonds due to thermomechanical stress at different climatic sites . Nevertheless, there are only few publications about outdoor exposure of modules and outdoor measurement techniques for cracks and fractures and fatigue of cell connectors due to temperature cycles and deformation …”

Section: Introductionmentioning

confidence: 99%

Evolution of cell cracks in PV‐modules under field and laboratory conditions

Buerhop‐Lutz

Wirsching

Bemm

et al. 2017

Progress in Photovoltaics

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Damaged modules, especially with cell cracks, can be observed quite often in photovoltaicinstallations. Little knowledge exists about long-term stability of precracked modules at real operating conditions. Previous investigations and existing standards focus on the degradation of new, defect-free modules. This work highlights a twofold approach for life-time study of precracked modules: (1) outdoor exposure of 54 precracked modules for 1 year and (2) artificial stressing of 20 representative precracked modules with a novel load test setup simulating snow and wind loads. The outdoor exposure reveals that at moderate weather conditions, no changes were detectable, neither in electric performance nor in EL-images. However, the accelerated static load tests with stepwise increasing pressures point out that above a certain threshold, cracks grow.Below this threshold, formerly unseen cracks become visible at the loaded stage. In addition, modules with a smaller number of damaged cells have a stronger tendency to degrade further than modules with an already large number of cracked cells. Remarkably, the power output measured with a solar simulator after a stress test up to 2500 Pa (describing conservative proof conditions for severe snow loads according IEC 61215) remains unchanged for almost all modules.

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Contact resistance measurement - observations on technique and test parameters

Cited by 16 publications

References 8 publications

High Hole Mobility Inorganic Halide Perovskite Field‐Effect Transistors with Enhanced Phase Stability and Interfacial Defect Tolerance

High Hole Mobility Inorganic Halide Perovskite Field‐Effect Transistors with Enhanced Phase Stability and Interfacial Defect Tolerance

Investigating the impact of SEM chamber conditions and imaging parameters on contact resistance ofin situnanoprobing

Evolution of cell cracks in PV‐modules under field and laboratory conditions

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