Photoelectric Conversion Device Off-Leakage Current Reduction
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Solution Overview
Problem
Conventional photoelectric conversion devices experience high off-leakage currents due to the thinness of the photoelectric conversion layer in inclined parts of the lower electrode, leading to potential cracks and increased electric current under reverse bias voltage.
Innovation Solution
A photoelectric conversion device structure is implemented where the lower electrode of the photodiode is connected to the drain electrode of a thin film transistor via a contact hole in a first insulating layer, with no photoelectric conversion layer directly above the contact hole, preventing the thinness and cracking issues.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a contact hole is secured directly below a photodiode to connect the lower electrode to the drain electrode, then electrical connection is achieved, but the photoelectric conversion layer becomes thin in the inclined part causing high off-leakage current
Solution Approach 1:
The patent extracts the photoelectric conversion layer from directly above the contact hole, creating a void space. This prevents the formation of thin inclined portions that cause high off-leakage current, while still maintaining electrical connection through the contact hole to the drain electrode.
Solution Approach 2:
The patent segments the photoelectric conversion layer structure by creating a discontinuity above the contact hole. The photoelectric conversion layer is present in regions where it is needed for light conversion but absent above the contact hole, dividing the structure into functional zones with different properties.
2Ease of manufacture
If the photoelectric conversion layer is made thin to accommodate the contact hole structure, then connection is enabled, but cracks occur in the i layer leading to increased reverse bias current
Solution Approach 1:
The photoelectric conversion layer is extracted or removed from the region directly above the contact hole, eliminating the thin, vulnerable sections that are prone to cracking. This maintains structural integrity while preserving electrical connectivity.
Solution Approach 2:
By preemptively removing the photoelectric conversion layer above the contact hole, the patent prevents future cracking and device failure. This prior removal acts as a cushioning measure that eliminates the root cause of reliability issues before they manifest.
3Area of stationary object
If photoelectric conversion layer is provided continuously over the lower electrode, then light conversion area is maximized, but off-leakage current increases due to thin inclined portions
Solution Approach 1:
The patent applies local quality by making the photoelectric conversion layer absent in the specific local region above the contact hole, while maintaining it in other regions. This localized modification reduces off-leakage current without significantly compromising the overall light conversion area.
Solution Approach 2:
The photoelectric conversion layer is taken out or removed from the specific area above the contact hole, creating a localized absence that prevents thin-layer formation and associated reliability issues while preserving the majority of the photoelectric conversion functionality.
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
This configuration significantly reduces the off-leakage current of the photodiode, improves light irradiation efficiency, and minimizes parasitic capacitance between electrodes.
Implementation Method 1
a photodiode including an upper electrode, a lower electrode, and a photoelectric conversion layer which is provided between the upper electrode and the lower electrode
Data Source
AI summary
An off-leakage current of a photodiode is reduced in a photoelectric conversion device. A photoelectric conversion device (100) includes: an oxide semiconductor layer (5) provided on a substrate (1); a passivation film (6) and a planarizing film (7) which are stacked on the oxide semiconductor layer; and a photodiode (9) including a lower electrode (91), a photoelectric conversion layer (92), and an upper electrode (93). The lower electrode is connected to a source electrode (4) via a contact hole provided in the passivation film and the planarizing film. No photoelectric conversion layer is provided directly above the contact hole.