Ambipolar OLET with Distributed Light Emission
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Solution Overview
Problem
Ambipolar organic light-emitting field effect transistors (OLETs) currently exhibit spatially confined light emission, limiting their application in fields requiring a large or distributed light source, such as ambient lighting and biomedical Point of Care applications, due to their narrow illuminated region.
Innovation Solution
An organic ambipolar light emitting field effect transistor with a three-layer architecture is developed, featuring a P-type semiconductor layer, a N-type semiconductor layer, and a light emitting layer, where the effective field-effect mobility ratios and energy band differences between these layers are optimized to achieve distributed light emission exceeding 20 μm, utilizing a Host-Guest system for modified light spectra.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If conventional ambipolar OLET structure is used, then light emission efficiency is enhanced, but illuminated region is confined and small
Solution Approach 1:
The patent applies local quality by creating different semiconductor layers with distinct properties (P-type and N-type) positioned at specific locations within the channel. The P-type layer is placed near the anode and the N-type layer near the cathode, with each layer having optimized thickness and mobility characteristics to control where recombination and light emission occur, thereby expanding the illuminated region from confined to distributed
Solution Approach 2:
The patent changes key parameters including the thickness of semiconductor layers (50-200 nm range), the effective field-effect mobility ratios (0.05 to 20), and energy band differences (0.2-1.0 eV for HOMO, 0.2-0.8 eV for LUMO) to transition from confined to distributed light emission. By adjusting these parameters, the device achieves broad illumination while maintaining high luminosity
2Ease of manufacture
If three-layer OLET device is used, then spatially confined illumination is generated, but diffused illumination capability is limited
Solution Approach 1:
The patent uses composite materials by combining P-type and N-type semiconductor layers with a light-emitting layer in a three-layer structure. Each layer is made of organic semiconductor materials with complementary properties, creating a composite system that enables both ease of manufacture through solution processing and versatility in achieving diffused illumination through proper material selection and layer design
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 transistor achieves a broad light emission spread over at least 20 μm, enhancing its applicability in various fields by ensuring a significant fraction of the ambipolar channel is illuminated, with effective field-effect mobilities within specific ranges to control and optimize light distribution.
Implementation Method 1
a light emitting layer adapted to allow recombination of charge carriers of opposite sign, interposed between said P-type semiconductor layer and said N-type semiconductor layer
Data Source
AI summary
An organic ambipolar light emitting field effect transistor having an architecture with layers stacked one over the other, adapted to generate a diffused illumination is described. The transistor has a gate electrode, a dielectric layer superposed to the gate electrode, an ambipolar channel superposed to the dielectric layer having a P-type semiconductor layer whose energy band is determined by its highest occupied molecular orbital HOMO-SCp and lowest unoccupied molecular orbital LUMO-SCp, a N-type semiconductor layer whose energy band is determined by its highest occupied molecular orbital HOMO-SCn and lowest unoccupied molecular orbital LUMO-SCn and a light emitting layer adapted to allow recombination of charge carriers of opposite sign, interposed between the P-type semiconductor layer and the N-type semiconductor layer, whose energy band is determined by its highest occupied molecular orbital HOMO-R and lowest unoccupied molecular orbital LUMO-R, respectively; a source electrode adapted to inject charges of a first type and a drain electrode adapted to inject charges of a second type, said source electrode and drain electrode being in contract with a same layer of said P-type or N-type semiconductor layers, the other of said semiconductor layers being in contact with the dielectric layer.