Short-Circuit Current

Source: AllumiaX Engineering

Understanding Short-Circuit Current in Solar Cells

The short-circuit current (I_SC) is the current flowing through a solar cell when the voltage across it is zero, essentially when it is short-circuited. It represents the maximum current that can be drawn from the solar cell.

Factors Affecting Short-Circuit Current

• Solar Cell Area: The larger the area of the solar cell, the higher the short-circuit current. Short-circuit current density (J_SC) is often used to normalize this factor.
• Light Intensity: The number of photons from the incident light source directly influences the short-circuit current. Higher light intensity results in a higher short-circuit current.
• Light Spectrum: The spectrum of the incident light, typically standardized to the AM1.5 spectrum, impacts the short-circuit current.
• Optical Properties: The absorption and reflection properties of the solar cell affect the short-circuit current.
• Minority-Carrier Collection Probability: This factor depends on the surface passivation and minority carrier lifetime in the base of the solar cell.

Calculating Short-Circuit Current

For solar cells of the same material type, the diffusion length and surface passivation are crucial material parameters affecting the short-circuit current. The short-circuit current density (J_SC) can be approximated by the equation J_SC = qG(L_n + L_p), where G is the generation rate, and L_n and L_p are the electron and hole diffusion lengths, respectively.

The short-circuit current (I_SC) is the product of the short-circuit current density (J_SC) and the cell area (A): I_SC = J_SC * A.

Maximum Short-Circuit Current in Silicon Solar Cells

Under the AM1.5 spectrum, silicon solar cells can achieve a maximum short-circuit current of 46 mA/cm². Laboratory measurements have shown short-circuit currents exceeding 42 mA/cm², while commercial solar cells typically range between 28 mA/cm² and 35 mA/cm².

Illuminated Current vs. Short Circuit Current

The light-generated current inside the solar cell (I_L) is often interchangeable with the short-circuit current (I_SC). In ideal conditions, every photon above the bandgap generates one charge carrier, leading to the highest current for the lowest bandgap.

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