Analysis of charge-injection characteristics at electrode-organic interfaces: Case study of transition-metal oxides
Bibliographic record
Abstract
The formation of resistance-free or Ohmic contacts at metal/organic interfaces remains a significant challenge for achieving high-performance organic electronic devices such as organic light-emitting diodes. Several oxides have recently been reported to yield extremely low-voltage devices and thus have excited a renewed interest in developing the next generation of contacting electrodes. In this paper, major metal oxides, CuO, ${\text{Cu}}_{2}\text{O}$, ${\text{Ni}}_{2}{\text{O}}_{3}$, ${\text{Co}}_{3}{\text{O}}_{4}$, ${\text{WO}}_{3}$, ${\text{MoO}}_{3}$, ${\text{V}}_{2}{\text{O}}_{5}$, and indium tin oxide, have been systematically studied to compare their relative performance as hole injection anodes, as well as to provide an experimental database for theoretical analysis of current-voltage $(IV)$ characteristics with a diverse range of injection barrier heights. Contrary to previous reports in the literature, none of the oxides studied in this work were found to form a true Ohmic contact with commonly used hole transport layers, such as N,N-diphenyl-N, N-bis-1-naphthyl-1--1-biphenyl-4,4-diamine ($\ensuremath{\alpha}$-NPD). This discrepancy is attributed to incorrect $IV$ data analysis of the quasi-Ohmic injection regime---the region in between space-charge limited current (SCLC) and injection limited current (ILC)---in previous studies. It is found that the quasi-Ohmic regime is much larger (i.e., covers a greater range of injection barrier height) than has previously been expected. A criterion that defines Ohmic, quasi-Ohmic, and injection limited contacts has been quantified based on a time-domain simulation of charge transport across $\ensuremath{\alpha}$-NPD single-carrier devices. This criterion includes the effects of the electric field dependent mobility, organic layer thickness, and charge-injection barrier height. The effects of the built-in potential on the $IV$ characteristics are also evaluated. A barrier-thickness-voltage ``phase'' diagram that defines the regions of SCLC, quasi-Ohmic, and ILC for $\ensuremath{\alpha}$-NPD is presented.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".