Abstract
The apparent carrier density profile measured by the capacitancevoltage technique in CdTe thin-film solar cells frequently displays a distinctive U-shape. We show that, even assuming a uniform carrier density, such a U-shape may arise from deep levels, a non-ohmic back-contact, and a thin absorber, which are commonly present in practical CdTe thin-film solar cells. A thin CdTe absorber contributes to the right branch of the U-shape due to a punch-through effect at reverse or zero biases, when the CdTe absorber is nearly fully depleted. A rectifying back-contact contributes to both branches of the U-shape due to voltage sharing with the front junction under a forward bias and early punch-through under a reverse bias. Deep levels contribute to the right branch, but also raise the bottom of the U-shape, leading to an overestimate of carrier density.
Original language | American English |
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Pages (from-to) | 126-131 |
Number of pages | 6 |
Journal | Solar Energy Materials and Solar Cells |
Volume | 100 |
DOIs | |
State | Published - May 2012 |
NREL Publication Number
- NREL/JA-5200-53927
Keywords
- Absorber thickness
- Back contact
- Capacitancevoltage
- CdTe
- Deep level