# Exercise 8.1-6

# Constructing Quantitative Logarithmic IV Characteristics

| Question 1. Construct rather quantitatively the logarithmic IV characteristics (= log j - eU plot) of two solar cells with the j1 and j2 values as given in the table. Here are a few hints:
|  | Draw first the straight lines for the two exponential terms resulting from the master equation (i.e. omit the "-1" term) into a log j - eU plot. Note that for room temperature kT = 0.025 eV or exp(eU/kT) = exp(40 · eU). Use the given numbers for the various ji = j(U = 0V) and calculate, for example, ji(U = 0.5 V) to get a second point. Correct by "hand" for the "-1" term (justify your reasoning) and add "by hand" the two resulting curves to the full characteristic. Repeat the procedure for a temperature of 400 K. Note, however, that all ji contain the intrinsic carrier density ni and that changing the temperature changes ni accordingly. |  |
| Calculated | Measured
--- | --- | ---
j1 | 1.6 · 10–14 A/cm2 | 10–9 A/cm2
j2 | 1.6 · 10–10 A/cm2 | 10–7 A/cm2
| Question 2: Determine the open circuit voltage UOC for room temperature and for 400 K and discuss your finding.
|  | Note: UOC is the voltage where the (positive) forward current in the dark is exactly equal to the magnitude of the photo current IPH

| Solution

With frame

Basic IU-Characteristics of Solar Cells

Solution to Exercise 8.1-3: Characteristics of Real Solar Cells

Solution to Exercise 8.1-6 Constructing Quantitative Logarithmic IV Characteristics

© H. Föll (Semiconductor Technology - Script)