Spiroxanthene Compound for OLED Electron Transport
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Solution Overview
Problem
Current organic light-emitting diodes (OLEDs) face challenges in achieving low operational voltage, high power efficiency, and good thermal characteristics, particularly due to uncertainties regarding the applicability of spiroxanthene-based compounds in electron transport and doped layers, which affect their thermal stability and hole blocking functions.
Innovation Solution
A compound according to Formula 1 is used in electron transporting or injecting layers, specifically designed to form a high-barrier hole blocking layer with a nominal thickness of less than 50 nm, enhancing thermal stability and electron transport capabilities, and can be combined with electrical dopants to improve conductivity and charge injection properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If conventional electron transporting materials are used in OLEDs, then the device can operate, but the operational voltage is high and power efficiency is low
Solution Approach 1:
The patent changes the chemical structure parameters of electron transporting materials by introducing specific molecular motifs (spiroxanthene core with dibenzofuran/dibenzothiophene units) and substituent groups (Formula 1 compounds) to optimize electronic properties. This structural parameter optimization enables lower operational voltage and improved power efficiency without sacrificing other device performance characteristics.
Solution Approach 2:
The patent employs composite material strategies by combining electron transporting materials with specific dopants (e.g., W2(hpp)4, Mo2(hpp)4) in defined ratios to create doped electron transporting layers. These composite layers achieve superior electrical conductivity and charge transport efficiency, directly addressing the high voltage and low power efficiency problems of conventional OLEDs.
2Productivity
If operational lifetime is increased to drive OLEDs with higher current densities, then higher luminous intensity is achieved, but operational temperature increases
Solution Approach 1:
The patent optimizes thermal parameters by selecting materials with high glass transition temperatures (Tg > 100°C, preferably Tg > 150°C) and high thermal stability. The specific molecular structure (Formula 1 compounds with rigid spiroxanthene cores) provides inherent thermal stability, allowing the device to operate at higher temperatures without degradation, thus enabling higher current densities and luminous intensity.
Solution Approach 2:
The patent uses electrically doped electron transporting layers with high conductivity to reduce operational voltage and power consumption, which indirectly reduces operational temperature. The doped layers (e.g., TPBi doped with W2(hpp)4) provide efficient charge transport that minimizes resistive heating, allowing sustained high luminous intensity without excessive temperature rise.
3Stability of the object's composition
If spiroxanthene-based materials are used to increase thermal stability, then thermal characteristics improve, but it remains unclear which compounds are suitable for specific functions like electron transport layers
Solution Approach 1:
The patent systematically varies structural parameters of spiroxanthene-based compounds (Formula 1) including substituent types (aryl, alkyl, haloalkyl groups), substituent positions, and molecular weight to optimize both thermal stability and functional properties. The patent provides concrete data (Tg, melting points, LUMO levels, electron mobility) to establish structure-property relationships, enabling selection of appropriate compounds for specific functions such as electron transport layers, electron injecting layers, and hole blocking layers.
Solution Approach 2:
The patent applies local quality by designing compounds with specific functional groups positioned at particular locations on the spiroxanthene core. Different substituent patterns (R1-R6 positions) provide localized electronic properties (HOMO/LUMO levels, electron affinity) that can be tuned for specific device functions. For example, compounds with electron-withdrawing groups enhance electron transport capability, while compounds with appropriate HOMO levels provide hole blocking functionality.
4Power
If high current densities are used to achieve higher luminous intensity, then power conversion efficiency must be very high, but this still results in higher operational temperature
Solution Approach 1:
The patent uses composite doped electron transporting layers combining electron transporting matrices (e.g., TPBi, TCTA, mCP) with appropriate dopants (W2(hpp)4, Mo2(hpp)4, Acridine Orange Base) to achieve high electrical conductivity. These composite layers reduce operational voltage and power consumption, thereby reducing operational temperature while maintaining high luminous intensity capability.
Solution Approach 2:
The patent optimizes electrical parameters (conductivity, electron mobility, LUMO levels) of electron transporting materials to maximize power conversion efficiency. The specific Formula 1 compounds provide optimal electronic parameters that minimize energy loss as heat, enabling high current density operation with controlled temperature rise.
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 use of the compound in OLEDs results in significantly reduced operational voltages and improved thermal stability, as demonstrated by experiments showing dramatic differences in performance compared to similar isomeric compounds, achieving high glass transition temperatures and efficient electron transport.
Implementation Method 1
it remains unclear, which of them may be generally useful in electronic devices, specifically, which of them may be suitable in specific functions not directly linked to light emission, e.g. as electron transport layers. Especially uncertain is their general applicability as undoped layers between the emitting layer and the cathode, due to the lack of a deep HOMO for the hole blocking function
Implementation Method 2
a first electron transporting layer, which is non-light emitting, between the light emitting layer and the first electrode, which first electron transporting layer comprises the compound according to formula 1
Implementation Method 3
The use of the compound in OLEDs results in significantly reduced operational voltages and improved thermal stability, as demonstrated by experiments showing dramatic differences in performance compared to similar isomeric compounds, achieving high glass transition temperatures
Data Source
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Figure 5~6
AI summary
The invention relates to a use of a compound according to formula (1), wherein each of R1, R2, R1, R2 is independently selected from H, C1-C6 alkyl, C1-C6 haloalkyl and C6-C10 aryl or both substituents on the same aromatic ring of the xanthene skeleton are hydrocarbyi groups linked with each other to form together an anelated divalent C2-C10 hydrocarbyi group; X and X' are independently selected from C and N, R5 is H if X is C, R5 is H if X' is C, R5 is lone electron pair if X is N, R5 is lone electron pair if X' is N, and each of R3, R4, R3, R4 is independently selected from H and C6-C10 aryl, with the proviso that neither both R3, R4 nor both R3, R4 are aryl at the same time and if X is C, R3and R4 are not H at the same time, and if X' is C, R3 and R4 are not H at the same time, or both substituents on the same phenyl or pyridyl ring are hydrocarbyi groups linked with each other to form together a divalent C4-C10 hydrocarbyi group representing an anelated, substituted or unsubstituted, six-membered aromatic ring; in an electron transporting layer or in an electron injecting layer comprised in an electronic device.