Photodiode Array Buffer Thickness for Reduced Electrode Leakage
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Solution Overview
Problem
Optical sensors using organic photodiodes experience leakage currents between adjacent lower electrodes due to the provision of buffer layers across multiple photodiodes.
Innovation Solution
A detection device with a substrate and photodiodes stacked in a specific order, featuring an insulating film between adjacent lower electrodes, where the lower buffer layer has varying thicknesses to create high resistance regions, reducing leakage currents.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a buffer layer is provided across multiple adjacent photodiodes to simplify manufacturing, then manufacturing ease is improved, but leakage currents occur between adjacent lower electrodes
Solution Approach 1:
The lower buffer layer is designed with spatially varying thickness: a first thickness over the lower electrode and a second thickness over the insulating film. This local quality variation allows the buffer layer to maintain electrical isolation at electrode boundaries (reducing leakage current) while remaining continuous across the photodiode array (maintaining manufacturing ease).
Solution Approach 2:
The thickness parameter of the lower buffer layer is changed across different regions. By making the thickness smaller over the insulating film compared to the electrode region, the electrical resistance increases at the electrode boundaries, effectively reducing leakage current while preserving the overall continuity of the buffer layer structure.
2Measurement precision
If the gap between adjacent lower electrodes is reduced to improve detection sensitivity, then detection precision is improved, but leakage currents increase between electrodes
Solution Approach 1:
The lower buffer layer exhibits different thickness characteristics in different spatial locations: thicker over electrodes and thinner over insulating films. This allows small electrode gaps to be used for improved detection precision while the thin buffer layer sections over insulating films maintain electrical isolation to prevent leakage currents.
Solution Approach 2:
The insulating film acts as an intermediary structure between adjacent lower electrodes. The lower buffer layer is designed to be thinner over this intermediary, allowing the buffer layer to conform to the insulating film and create a natural electrical barrier that prevents leakage currents even when electrodes are closely spaced.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The configuration effectively minimizes leakage currents and enhances detection sensitivity and definition by maintaining a smaller gap between electrodes, improving the overall performance of the detection device.
Implementation Method 1
an insulating film provided between a plurality of the adjacent lower electrodes
Implementation Method 2
A thickness of the insulating-film overlap portion of the lower buffer layer is smaller than a thickness of the electrode-overlap portion of the lower buffer layer
Implementation Method 3
Optical sensors capable of detecting fingerprint patterns and vascular patterns are known... each include a plurality of photodiodes
Data Source
AI summary
According to an aspect, a detection device includes: a substrate; a plurality of photodiodes in which a lower electrode, a lower buffer layer, an active layer, an upper buffer layer, and an upper electrode are stacked on the substrate in the order as listed; and an insulating film provided between a plurality of the adjacent lower electrodes. The lower buffer layer includes an electrode-overlap portion that overlaps the lower electrode and an insulating-film overlap portion that overlaps at least a portion of the insulating film. A thickness of the insulating-film overlap portion of the lower buffer layer is smaller than a thickness of the electrode-overlap portion of the lower buffer layer.