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.

What it covers

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 doesn't 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.

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.

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