Direct Semiconductor Solar Cell With a Continuous Depletion Channel
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Solution Overview
Problem
Wide bandgap photovoltaic cells, particularly those using direct semiconductors, face inefficiencies due to rapid carrier recombination and the reduction of the depletion region thickness under load voltage, leading to reduced energy conversion efficiency.
Innovation Solution
A photovoltaic cell design featuring a direct semiconductor with a transparent biasing agent and a collector forming distinct depletion regions, creating a continuous minority carrier channel that minimizes recombination and maintains depletion region thickness under load conditions, utilizing a dielectric material with fixed charges to enhance the channel's stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If a direct semiconductor is used in a wide bandgap photovoltaic cell, then light absorption efficiency is improved, but carrier recombination occurs rapidly reducing energy conversion efficiency
Solution Approach 1:
The photovoltaic cell is divided into multiple depletion regions separated by neutral regions. Each depletion region is formed by contacts with different Fermi levels, creating distinct zones for carrier separation and collection. This segmentation allows efficient light absorption in each region while minimizing recombination through proper spatial distribution of carriers.
Solution Approach 2:
Different regions of the semiconductor are given different electrical properties through the use of contacts with varying Fermi levels. The biasing agent contact creates a first depletion region with specific properties, while the collector contact creates a second depletion region with different properties. This local differentiation optimizes both light absorption and carrier collection in各自 regions.
2Power
If load voltage is applied to a Schottky cell, then power delivery is enabled, but the depletion region thickness is reduced leading to lower efficiency
Solution Approach 1:
The cell structure segments the depletion regions such that the first depletion region (formed by the biasing agent) and second depletion region (formed by the collector) are spatially separated by a neutral region. This segmentation allows the depletion regions to maintain their thickness even under load voltage, as the neutral region acts as a buffer that prevents the depletion regions from collapsing into each other.
Solution Approach 2:
The neutral region acts as an intermediary between the two depletion regions. It provides a transition zone that maintains the integrity and thickness of both depletion regions under load conditions, preventing the harmful reduction of depletion width that would otherwise occur in conventional Schottky cells.
3Use of energy by moving object
If a transparent biasing agent and collector are used to form depletion regions, then device complexity increases, but energy conversion efficiency is enhanced
Solution Approach 1:
The contacts in this structure serve multiple functions: they establish depletion regions for carrier separation, provide electrical connections for power extraction, and create the necessary Fermi level differences for efficient operation. The biasing agent contact both forms the first depletion region and provides a reference potential, while the collector contact forms the second depletion region and collects carriers. This multi-functionality reduces the need for additional separate components.
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 design enhances the energy conversion efficiency by reducing recombination losses and maintaining the depletion region's integrity, resulting in higher open-circuit voltage, short-circuit current, and fill factor compared to traditional Schottky cells.
Implementation Method 1
As light impinges on the semiconductor material, absorption of incoming photons promotes electrons from the valence band of the semiconductor material to the conduction band, thus creating an increased number of charge carrier pairs
Implementation Method 2
The Fermi levels come into equilibrium with one another by diffusion of electrons from the n-type semiconductor into the p-type semiconductor. This leaves a portion of the n-type semiconductor near the junction positively charged and a portion of the p-type semiconductor near the junction negatively charged. These portions constitute a 'space charge region' and create an electric field in the vicinity of the junction
Data Source
AI summary
A photovoltaic cell includes a semiconductor element (20) formed from a direct semiconductor and a transparent biasing agent (28) overlying a first portion of the front face (22) of the semiconductor, the biasing agent producing a first depletion region (30) in the semiconductor element. A collector (40) directly contacts a second portion of the front face. The collector produces a second depletion region (44) in the semiconductor element. The collector (40) is out of direct conductive contact with the biasing agent (28) but in proximity to the biasing agent. A continuous region at least partially depleted of majority carriers extends between the first and second depletion regions at the front face of the semiconductor element. The continuous region may include overlapping portions of the first and second depletion regions (30,44), or may include an additional depletion region (160) formed by a charged dielectric (147).