# How to Make High-Efficiency Solar Cells with Stacked Layers > This patent describes a solar cell design that stacks two different types of light-absorbing layers, cadmium telluride and silicon, connecting them in parallel to capture more sunlight efficiently. - **Patent:** US 9287431 - **Original title:** Superstrate sub-cell voltage-matched multijunction solar cells - **Owner:** Alliance for Sustainable Energy - **Granted:** 2016 - **Status:** Active - **Times cited:** 18 - **Field:** renewable_energy, semiconductors, consumer_electronics, materials ## What it does This patent describes a special type of solar cell called a multijunction cell. It combines an "upper sub-cell" made of cadmium telluride (CdTe) with a "lower sub-cell," often made of silicon (Si), as stated in claim 1 and claim 2. These two sub-cells are separated by a transparent insulating layer and are designed to be "voltage-matched," meaning they produce similar electrical pressure. Crucially, they are connected in parallel (claim 1), which allows their currents to add up while maintaining a consistent voltage. Light enters through a transparent "superstrate," like glass (claim 9), hitting the CdTe layer first, then passing through to the lower Si layer. For example, a solar panel could use this design to convert a broader spectrum of sunlight into electricity than a single-layer cell. ## What it does NOT cover - Solar cells where the different light-absorbing layers are connected in series, rather than in parallel. - Multijunction solar cells that do not use a cadmium telluride (CdTe) upper sub-cell. - Designs where the upper and lower sub-cells are not specifically "voltage-matched." - Solar cells that do not include a transparent insulating layer between the upper and lower sub-cells. - Lower sub-cells that lack an interdigitated p-type and n-type back contact made of Si, as specified in claim 1. ## The clever bit The innovation lies in combining two distinct solar cell materials (like CdTe and Si) into a stacked "multijunction" design where they are specifically "voltage-matched" and connected in parallel. This allows each layer to be optimized independently for different parts of the solar spectrum and then combined without the current mismatch problems often seen in serially connected stacked cells. ## Real-world examples 1. High-efficiency research solar cells 2. Next-generation thin-film solar panels 3. Concentrator photovoltaics (CPV) 4. Space-based solar arrays ## Why it matters Solar cells that can capture more of the sun's energy are crucial for making solar power more affordable and widespread. This patent offers a way to combine different materials, like CdTe and Si, each good at absorbing different parts of the light spectrum, into a single, more efficient device. This approach helps overcome limitations of single-material solar cells and could lead to higher power output from solar panels. ## Frequently asked questions ### What does How to Make High-Efficiency Solar Cells with Stacked Layers cover? This patent describes a solar cell design that stacks two different types of light-absorbing layers, cadmium telluride and silicon, connecting them in parallel to capture more sunlight efficiently. ### Who owns patent US 9287431? Alliance for Sustainable Energy owns this patent, granted in 2016. ### When does this patent expire? This patent is expected to expire on April 2, 2034, when the invention enters the public domain. ### What is patent US 9287431 cited by? This patent has been cited by 18 later patents that build on its ideas. ### What problem does this patent solve? Solar cells that can capture more of the sun's energy are crucial for making solar power more affordable and widespread. This patent offers a way to combine different materials, like CdTe and Si, each good at absorbing different parts of the light spectrum, into a single, more efficient device. This approach helps overcome limitations of single-material solar cells and could lead to higher power output from solar panels. ### What does this patent NOT cover? Solar cells where the different light-absorbing layers are connected in series, rather than in parallel. **Full plain-English explainer:** https://patentbrief.org/patent/us/9287431/superstrate-sub-cell-voltage-matched-multijunction-solar-cells **Original patent:** https://patents.google.com/patent/US9287431 --- _Source: PatentBrief — https://patentbrief.org. Patent facts are from public records; the plain-English explanation is PatentBrief's._ ## Related patents Semantically similar inventions in the PatentBrief corpus: - [Solar Cells Made of Stacking Layers with Different Energy Gaps](https://patentbrief.org/patent/us/8912428/high-efficiency-multijunction-ii-vi-photovoltaic-solar-cells) — This patent describes a solar cell built by stacking multiple layers, each designed to capture a different part of the light spectrum for maximum energy conversion, achieving high efficiency. - [How a Special Box Turns Solar Panel Power into Home Electricity](https://patentbrief.org/patent/us/9391457/apparatus-and-method-for-producing-ac-power) — This patent describes a device that takes the unique direct current (DC) electricity from each layer of a special multi-layer solar panel and converts it into alternating current (AC) electricity usable in homes, making sure to get the most power out of each layer. - [Solar Cells with Built-in Smart Electronics on the Back](https://patentbrief.org/patent/us/9293619/smart-photovoltaic-cells-and-modules) — This patent describes a solar cell design that integrates electronic components, like a bypass switch, directly onto the back of the cell to improve performance, especially when parts of the cell are shaded. - [How the First Practical Silicon Solar Cell Works](https://patentbrief.org/patent/us/2780765/solar-cell-photovoltaic) — A 1954 invention by Bell Labs researchers that created the first silicon-based solar cell capable of converting sunlight into enough electricity to power everyday devices. - [How Amorphous Silicon Changed Solar Power](https://patentbrief.org/patent/us/4064521/semiconductor-device-having-a-body-of-amorphous-silicon) — This 1976 patent describes using a specific form of non-crystalline silicon to create cheap, thin semiconductor devices like solar cells.