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 With frame as PDF

go to Basic IU-Characteristics of Solar Cells

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

go to Solution to Exercise 8.1-6 Constructing Quantitative Logarithmic IV Characteristics

© H. Föll (Semiconductor Technology - Script)