---
title: "Characteristics curve of solar cell"
subject: "Energy Environment and Society"
chapter: 3
key: "semester_7/energy_environment_and_society:solar-cell-characteristics-curve"
source: https://www.bctengineer.com/q/semester_7/energy_environment_and_society/solar-cell-characteristics-curve
site: BCT Engineering
---

# Characteristics curve of solar cell

Energy Environment and Society · Chapter 3: Renewable Energy Sources

- Asked in: 2070 Asar, 2 marks; year not given
- Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_7/energy_environment_and_society/solar-cell-characteristics-curve
- Whole chapter: https://www.bctengineer.com/md/semester_7/energy_environment_and_society/chapter-3

## Question

Describe the characteristics (I-V curve) of a solar cell.

## Short answer

The I-V curve shows current vs voltage; key points are short-circuit current Isc, open-circuit voltage Voc (~0.6 V), and maximum power point (Vmpp, Impp). Fill factor FF = Pmax/(Isc·Voc) (~0.7–0.85); efficiency η = Pmax/(G·A). Higher temperature reduces Voc and power (~0.4–0.5%/°C).

## Answer

The **I-V characteristic** of a solar cell shows the relation between the output current and voltage under constant sunlight and temperature. The equivalent circuit is a current source (photocurrent Iph) in parallel with a diode, with small series and shunt resistances.

I = Iph − I₀ [exp(qV / nkT) − 1]

```text
 I (A)
 Isc |-----------.
     |            '.
     |   MPP -> *   '.
     |          |     '.
     |          |       |
     +----------+-------+---- V
              Vmpp     Voc
```

#### Important points
- **Short-circuit current (Isc):** current at V = 0; it is directly proportional to the irradiance.
- **Open-circuit voltage (Voc):** voltage at I = 0 (about 0.6 V for silicon); it rises only slowly (logarithmically) with irradiance and drops with temperature.
- **Maximum power point (MPP):** the point (Vmpp, Impp) where the product V×I is largest. Pmax = Vmpp × Impp.
- **Fill factor (FF):** FF = Pmax / (Voc × Isc), usually 0.7–0.85. It shows the squareness of the curve.
- **Efficiency:** η = Pmax / (G × A), where G is irradiance and A is the cell area.

Effect of sunlight: higher irradiance raises the current (curve moves upward). Effect of temperature: higher temperature reduces Voc (about −2 mV/°C per cell), and hence reduces power (about −0.4 to −0.5% per °C).

## Check yourself

The answer's key points as multiple-choice questions, with the correct option and why.

1. Where is the short-circuit current measured and how does it vary with irradiance?
   A. At I = 0; independent of irradiance
   B. At V = 0; directly proportional to irradiance
   C. At V = 0; logarithmic in irradiance
   D. At the maximum power point; inversely proportional
   Answer: B. Isc is at zero voltage and scales linearly with irradiance; Voc rises only logarithmically. (Key point: Isc and Voc)

2. What is the fill factor?
   A. Pmax / (Voc x Isc)
   B. Voc / Isc
   C. Pmax / (G x A)
   D. Vmpp / Impp
   Answer: A. FF shows how square the I-V curve is, typically 0.7-0.85. (Key point: Fill factor)

3. What happens to a cell when temperature rises?
   A. Voc rises and power rises
   B. Isc drops to zero
   C. Nothing changes
   D. Voc and power decrease
   Answer: D. Voc falls about 2 mV/deg C per cell, reducing power by about 0.4-0.5% per deg C. (Key point: Temperature effect)

## Related in Energy Environment and Society

- [Solar radiation, solar cell and plant](https://www.bctengineer.com/question.md?key=semester_7%2Fenergy_environment_and_society%3Asolar-radiation-cell-plant) — Energy Environment and Society, chapter 3
- [Solar cell principle and applications](https://www.bctengineer.com/question.md?key=semester_7%2Fenergy_environment_and_society%3Asolar-cell-principle-applications) — Energy Environment and Society, chapter 3
- [Working of a solar cell](https://www.bctengineer.com/question.md?key=semester_7%2Fenergy_environment_and_society%3Asolar-cell-working) — Energy Environment and Society, chapter 3
- [Biomass conversion, IV curve, wind mapping](https://www.bctengineer.com/question.md?key=semester_7%2Fenergy_environment_and_society%3Abiomass-iv-curve-wind-mapping) — Energy Environment and Society, chapter 3

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