Junction Properties of nip and pin Amorphous Si Solar Cells Prepared by a Glow Discharge in Pure Silane

Abstract

The junction properties of various a·Si solar cell structures have been studied in some detail. Various structures of a·Si solar cells such as pin, nip, pp^-n, and nn^-p structures were prepared. The nip solar cell gave a conversion efficiency of 6.86% under AMI (100 mW/cm²) insolation through its n-layer. It is demonstrated experimentally and theoretically that the opto-electronic properties of the undoped layers of a·Si solar cells were influenced by residual impurities. The nip cell is shown to be of an np^-p or np^-p structure because of the residual boron during the deposition process, and gives a higher conversion efficiency under illumination through its n-layer than through the p-layer. The current transport mechanism is shown to depend on the electrical properties of the central (normally undoped) region. Doping the central region with boron causes a decrease in the injection current component into p-layer, and hence an increase in the n-value and the open-circuit voltage.