Photovoltaic Device Bilayer Polymorphs Near-Infrared Absorption
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Solution Overview
Problem
Organic solar cells have low power conversion efficiency due to limited light absorption, particularly in the near-infrared range, as the materials used do not optimally match the solar spectrum, resulting in a significant fraction of light energy being lost and not converted into electrical current.
Innovation Solution
A photovoltaic device with a semiconducting bilayer structure, where one sublayer comprises a first polymorph and the other sublayer comprises a different polymorph of metallophthalocyanine, enhancing light absorption and charge generation by complementing their absorption profiles, and including additional layers such as an electron transporting layer and hole blocking layers to improve efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a single metallophthalocyanine material is used in organic solar cells, then the device structure is simple and easy to manufacture, but the light absorption range is narrow and power conversion efficiency is low
Solution Approach 1:
The patent employs a bilayer composite structure where two different polymorphs of metallophthalocyanine (Form I and Form II) are combined in sequential layers. Form I absorbs light primarily in the 400-600 nm range while Form II absorbs in the 600-900 nm range, creating a composite material system with complementary absorption profiles that together cover a broader portion of the solar spectrum, thereby resolving the contradiction between manufacturing simplicity and power conversion efficiency.
Solution Approach 2:
The active layer is segmented into two distinct sublayers, each containing a specific polymorph of metallophthalocyanine. This segmentation allows each layer to specialize in absorbing different wavelength ranges, with Form I handling shorter wavelengths and Form II handling longer wavelengths including the near-infrared region, thus improving overall light capture without requiring complex multi-material composites.
2Use of energy by moving object
If metallophthalocyanine materials are used to capture near-infrared light, then the absorption coefficient is high, but the absorption profile remains narrow and cannot capture the full solar spectrum
Solution Approach 1:
Each polymorph layer is optimized for specific local absorption characteristics: Form I is positioned to maximize absorption in the visible range (400-600 nm) while Form II is optimized for the near-infrared range (600-900 nm). This local quality optimization allows each layer to excel at its designated wavelength range while the combined structure achieves broad-spectrum coverage, resolving the contradiction between high absorption coefficient and broad spectrum adaptability.
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 bilayer structure increases the power conversion efficiency by capturing a broader range of light energy, particularly in the near-infrared spectrum, leading to improved current generation and voltage retention, with a demonstrated increase in short circuit current and overall efficiency from 1.50% to 2.35%.
Implementation Method 1
The photoactive layer can absorb the energy in a photon emitted by radiation, such as sunlight. This photon energy creates an exciton, or bound electron-hole pair.
Implementation Method 2
Disclosed in various embodiments herein are photovoltaic devices that have an improved overall power conversion efficiency (PCE). Generally speaking, the photovoltaic devices include a first electrode (such as an anode), a semiconducting bilayer having two continuous sublayers, and a second electrode (such as a cathode).
Data Source
AI summary
A photovoltaic device is disclosed. The photovoltaic device includes a substrate, an anode, a cathode, and a semiconducting bilayer. The bilayer is composed of a first continuous sublayer and a second continuous sublayer. The first sublayer includes a first polymorph of a metallophthalocyanine. The second sublayer includes a second polymorph of the same metallophthalocyanine. The complementary absorption profiles of the polymorphs result in a device having greater absorption and efficiency, improving performace of the photovoltaic device.