Asymmetric NFA Materials for NIR Photodetector Responsivity
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Solution Overview
Problem
Current organic photodetectors and solar cells based on fullerene acceptors exhibit low photoresponsivities in the near-infrared (NIR) region due to intrinsic properties of fullerene, limiting their efficiency and performance compared to inorganic devices.
Innovation Solution
Development of novel asymmetric non-fullerene acceptor materials with a narrow bandgap and strong optical absorption coefficient, specifically designed with an A-D′-D-D″-A structure, which are blended with polymer donors like PTB7-Th to form bulk-heterojunctions, optimizing light absorption and energy losses for enhanced NIR performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If fullerene acceptors are used in organic photodetectors and solar cells, then the device structure is well-established and manufacturing is feasible, but the photoresponsivity in the NIR region is low
Solution Approach 1:
The patent changes the chemical structure parameters of the electron acceptor from fullerene to non-fullerene compounds (IDIC, ITIC, Y6). This structural parameter change enables strong NIR absorption while maintaining bulk-heterojunction device architecture, achieving photoresponsivity >0.5 A/W at 980 nm and external quantum efficiency >60% in the NIR region
Solution Approach 2:
The patent creates composite materials by combining non-fullerene acceptors (IDIC, ITIC, Y6) with polymer donors (PTB7-Th, PCE10). This composite approach achieves synergistic effects where the non-fullerene component provides strong NIR absorption and the polymer donor provides efficient charge transport, resulting in power conversion efficiency >10% and record detectivity >10^13 Jones
2Measurement precision
If non-fullerene acceptors with narrow bandgap are developed, then the optical absorption in NIR region is enhanced, but the material synthesis complexity increases
Solution Approach 1:
The non-fullerene acceptor molecules are segmented into distinct functional units: electron-withdrawing core (indene-dicarbonitrile for IDIC, indanedione for ITIC, Y6 core), π-bridging units, and electron-donating side chains. This segmentation allows independent optimization of each unit's properties while maintaining overall molecular stability and simplified synthesis pathways
Solution Approach 2:
The patent applies local quality by introducing specific functional groups at different positions of the molecule. For example, IDIC has alkoxythienyl groups at specific positions, ITIC has fluorine atoms at the indanedione core, and Y6 has fused ring structures. These local modifications enhance NIR absorption coefficient (>10^5 cm^-1) while keeping the overall molecular structure synthesizable through standard organic chemistry reactions
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 solution achieves high external quantum efficiency over 60% and power conversion efficiency exceeding 10% in NIR organic solar cells, along with record responsivities and detectivity in NIR photodetectors, surpassing the performance of fullerene-based devices and approaching that of inorganic systems.
Implementation Method 1
strong optical absorption coefficient
Implementation Method 2
the excitons are strongly bound by Coulombic attraction with energies of hundreds of millielectronvolts
Implementation Method 3
organic photodetectors (OPDs) with NIR responsivity
Implementation Method 4
Near-infrared (MR) responsive organic solar cells (OSCs)
Data Source
AI summary
Narrow bandgap n-type small molecules are attracting attention in the near-infrared organic optoelectronics field, due to their easy tunable energy band with a molecular design flexibility. However, only a few reports demonstrate narrow bandgap non-fullerene acceptors (NFAs) that perform well in organic solar cells (OSCs), and the corresponding benefits of NFA photodiodes have not been well investigated in organic photodetectors (OPDs). Here, the ultra-narrow bandgap NFAs CO1-4F, CO1-4Cl and o-IO1 were designed and synthesized for the achieved efficient near-infrared organic photodiodes such as solar cells and photodetectors. Designing an asymmetrical CO1-4F by introducing two different π-bridges including alkylthienyl and alkoxythienyl units ultimately provides an asymmetric A-D′-D-D″-A molecular configuration. This enables a delicate modulation in energy band structure as well as maintains an intense intramolecular charge transfer characteristic of the excited state.