Optical Sensor Texture Structure for Light Trapping
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Solution Overview
Problem
Optical sensors face challenges in achieving high photoelectric conversion efficiency due to the limitations of thin film absorption layers, which are optically very thin and struggle to balance multipass absorption and antireflection, leading to difficulties in manufacturing and electrode contact reliability.
Innovation Solution
A semiconductor optical sensor with a light absorption medium having a refractive index and thickness less than the light transmission length, featuring a texture structure on the light incident surface with a random surface direction and a structure scale between (λ/n) and λ, combined with a light reflector on the opposite surface, to achieve both optical trap and moth eye effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the thickness of the light absorption medium is increased to improve light absorption efficiency, then the light absorption probability increases, but the background noise component increases substantially and the extraction efficiency of photocurrent decreases
Solution Approach 1:
The patent applies surface texturing that creates curved or non-planar interfaces on the light incident surface of the thin film absorption layer. This curvature randomizes the direction of internal reflection of light at the semiconductor interface, enhancing the probability of total internal reflection and trapping light inside the thin absorption medium for multiple passes, thereby improving light absorption efficiency without increasing thickness.
2Object-generated harmful factors
If the thickness of the light absorption medium is decreased to reduce background noise and improve response time, then the signal-to-noise ratio improves, but the light absorption efficiency decreases
Solution Approach 1:
By introducing curved surface textures on the thin film absorption layer, the patent enables multiple internal reflections and light trapping within the reduced thickness, compensating for the decreased absorption path length and maintaining high light absorption efficiency despite the reduced thickness.
Solution Approach 2:
The surface texturing creates periodic or quasi-periodic structures that induce multiple passes of light through the absorption medium. This periodic interaction between light and the textured surface ensures sufficient absorption probability even in thin films, allowing the device to achieve both low noise and high absorption efficiency.
3Reliability
If a complex double hierarchical hybrid texture structure is formed to achieve both optical trap effect and moth eye effect, then light absorption in wide wavelength region is enhanced, but manufacturing complexity and difficulty increase substantially
Solution Approach 1:
The patent merges the optical trap effect and moth eye effect into a single integrated surface texture structure. By combining these two effects in one unified texture design, the patent achieves enhanced light absorption across a wide wavelength region while avoiding the manufacturing complexity of forming separate double hierarchical structures.
Solution Approach 2:
The surface texture structure is designed to perform multiple functions simultaneously: it provides both the optical trap effect for enhanced light trapping and the moth eye effect for antireflection. This multi-functional design simplifies the overall device structure and manufacturing process while achieving superior light absorption performance.
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
This configuration enables a high photoelectric conversion efficiency by enhancing multipass absorption and antireflection, addressing the limitations of thin film sensors and improving manufacturing reliability without complex texture structures.
Implementation Method 1
enhance a probability of light being totally reflected at an internal interface of a medium thus enhancing a probability of light being trapped inside a semiconductor
Implementation Method 2
randomizing a direction of internal reflection of light at a semiconductor interface having a high refractive index. When an optical trap occurs effectively, a probability that light passes through an absorption medium a plurality of times increases
Implementation Method 3
Photoelectric conversion elements have been used for a plurality of purposes. Important examples include a solar cell aiming to collect useful energy from sunlight and an optical sensor aiming to acquire useful information related to a target from observation light
Data Source
AI summary
In order to provide an optical sensor that is capable of obtaining both an optical trap effect and a moth eye effect with a single texture structure, a semiconductor optical sensor according to the present invention includes a light absorption medium that has a refractive index n and a thickness sufficiently less than a light transmission length, wherein the center wavelength to be observed is defined as λ. The semiconductor optical sensor is characterized by: having, in a light incident surface, a texture structure having a random surface direction and a typical structure scale d defined as in (λ/n).