Acridonic Copolymers for Low Band-Gap Solar Cells
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Solution Overview
Problem
Current photovoltaic devices using organic and polymer materials have low efficiency due to high band-gap values in donor compounds, limiting their ability to effectively convert solar radiation into electric energy, especially in the visible spectrum region.
Innovation Solution
Development of alternating π-conjugated copolymers based on acridonic units with low band-gap values, specifically around 2.0 eV or lower, which are used as electron-donor compounds in photovoltaic devices, enhancing their ability to capture and convert solar radiation within the visible spectrum.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional donor compounds with high band-gap values are used, then the material stability and ease of manufacture are maintained, but the light harvesting efficiency and energy conversion capability deteriorate
Solution Approach 1:
The patent applies parameter changes by systematically modifying the chemical structure of donor compounds through copolymerization. Specifically, it combines units with electron-donating groups (like thiophene) with units containing electron-accepting groups (like pyridine or pyrimidine), thereby tuning the HOMO-LUMO energy gap to lower values (around 2.0 eV) while maintaining synthetic feasibility through established polymerization methods
Solution Approach 2:
The patent employs composite materials by creating alternating copolymers that integrate two distinct functional units: electron-donating units (providing structural stability and ease of synthesis) and electron-accepting units (reducing band-gap). This composite structure allows the material to simultaneously achieve low band-gap for improved light harvesting and maintain manufacturing advantages from well-established polymer chemistry
2Productivity
If the band-gap is reduced to improve visible spectrum absorption, then the light harvesting efficiency improves, but the voltage output and energy quality deteriorate
Solution Approach 1:
The patent applies local quality by creating alternating sequences of electron-donating and electron-accepting units within the polymer chain. This local alternation of electronic properties allows different segments of the same material to contribute differently: the electron-donating units maintain higher energy levels for voltage generation, while the electron-accepting units facilitate lower energy gap for visible light absorption, achieving both goals simultaneously within a single material system
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
These copolymers improve the light harvesting process and efficiency of photovoltaic devices by effectively converting solar radiation within the visible spectrum, surpassing the limitations of existing materials with higher band-gap values.
Implementation Method 1
absorption of a photon on the part of the donor compound with the formation of an exciton, i.e. a pair of 'electron-hole' charge carriers
Implementation Method 2
Photovoltaic devices are devices capable of converting the energy of a light radiation into electric energy
Implementation Method 3
diffusion of the exciton in a region of the donor compound in which its dissociation can take place
Implementation Method 4
dissociation of the exciton in the two charge transporters (electron (−) and hole (+)) separated
Implementation Method 5
transporting of the charges thus formed to the cathode (electron, through the acceptor compound) and anode (hole, through the donor compound), with the generation of an electric current in the circuit of the device
Data Source
AI summary
The present invention relates to copolymers for solar cells based on acridonic units comprising: a monomeric unit (A) having general formula (I) wherein X is S or Se, Y is 0, S or NR′ and R, R′, the same or different, are C4-C24 alkyl groups, aryl groups optionally substituted with other functional groups, acyl groups or thioacyl groups; at least one monomer unit (B) having general formula (II) wherein Z is 0, S, Se or N—R″, wherein R″ is a C4-C24 alkyl group, an aryl group optionally substituted with other functional groups, an acyl group or thioacyl group, said monomeric unit (B) being connected to any position available of a hetero-aromatic side ring of the unit (A) through one of the two positions indicated by the dashed lines in general formula (II). Photovoltaic devices comprising said alternating π-conjugated polymers are also described.