Single-diode cell: photocurrent vs irradiance, ideality n, temperature; I(V), power P(V), maximum-power point.
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About this model
A single-diode photovoltaic cell model generates the I–V curve from photocurrent set by irradiance, diode ideality factor n, and temperature-dependent diode behavior in the exponential law. From I(V) the simulator also plots power P(V) = I·V and marks the maximum-power point (MPP) where dP/dV = 0 on the power curve. Assumptions: one lumped diode and series/shunt representation typical of teaching single-diode models—no multi-junction cells, partial shading hotspots, or a full thermal network of the module. Vary irradiance, ideality n, and temperature to see short-circuit current, open-circuit voltage, fill factor, and how the MPP shifts on the I(V) and P(V) curves.
Who it's for: Intermediate renewable energy, semiconductor devices, and introductory photovoltaics courses.
Key terms
solar cell I–V curve
maximum power point
photocurrent
ideality factor
open-circuit voltage
irradiance
How it works
Educational single-diode solar cell: I = Iᵖʰ − I₀(e^(V/nVₜ)−1) with photocurrent scaled by irradiance. Series/shunt resistances omitted for clarity; MPP is located numerically on the I–V sweep.
Key equations
Iᵖʰ ∝ G, Vₜ ≈ (kT/q)·n
Frequently asked questions
Why does higher irradiance mainly raise I_sc?
Photocurrent scales roughly with the number of absorbed photons, so short-circuit current tracks irradiance almost linearly. Open-circuit voltage rises only logarithmically with photocurrent, so students who expect V_oc to double with twice the light are misled by the diode exponential.
What is the maximum-power point?
It is the bias where P = I·V is largest—neither short-circuit (I max, V=0) nor open-circuit (V max, I=0). MPPT controllers hunt that knee; operating at V_oc or I_sc alone delivers zero average power to a DC load.
How does temperature usually hurt performance?
Rising temperature typically lowers V_oc more than it helps current, shrinking the power rectangle. Ideality n stretches the diode knee and can soften the fill factor; this lab’s single-diode curves show those qualitative shifts without a full datasheet thermal model.