REVIEW ON BACK CONTACT SCHOTTKY BARRIER OF CDTE SOLAR CELL

Abstract

The presence of a back-contact barrier always affects the current–voltage characteristics of thin-film CdS/CdTe/metal solar cells initially by impeding hole transport, a current-limiting effect generally referred to as “rollover.†In this case, the CdS/CdTe solar cell with a CdTe/metal back-contact barrier is modeled by two exactly opposite polarised diodes in series.Analytic simulations are engulfed to the measured current–voltage curve, the voltage distribution between the two diodes is shown under different conditions, and the back-contact barrier height is extracted from them. Room-temperature barrier heights exceeding 0.5 eV will always result in consequent fill-factor reduction. The back contact on CdTe based solar cells is responsible for the non-idealities in the cell characteristics. Numerical modelling of the thin film cells supports this expectation, a simple model can elaborate all quantitative and qualitative non-idealities like rollover and roll-factor loss in I±V curves, the shape and frequency totally dependence of CV curves. A more elementary way to get convinced by the need of the back contact is the use of monochromatic light which invade this contact. For CdTe, this comes to the light of at around 840 nm. The effect of the light in this wavelength region on the I±V characteristics is studied in this paper. It was observed that the I±V curves were only affected by photons within this wavelength region. This can be described by the creation of a new charge carrier distribution in the adjacent contact.