Electrical detection of electron spin resonance in microcrystalline silicon pin solar cells

Abstract

Pulsed electrically detected magnetic resonance (pEDMR) was employed to study spin-dependent processes that influence charge transport in microcrystalline silicon (µc-Si:H) pin solar cells. Special emphasis was put on the identification of the signals with respect to the individual layers of the cell structure. To do this, we systematically modulated the morphology of the highly doped n- and p-layers from amorphous to microcrystalline. By combining the information obtained from low-temperature (T = 10 K) pEDMR spectra and from the deconvoluted time evolution of spectrally overlapping resonances, we found signals from conduction band tail states as well as phosphorus donor states in samples containing an amorphous n-type layer and a resonance associated with valence band tail states in samples with an amorphous p-layer. Moreover, several signals from the intrinsic microcrystalline absorber layers could be identified. An additional resonance at g = 1.9675(5), which has not been observed in EDMR before, was found. We assign this signal to shallow donors in the Al-doped ZnO layer, which is commonly used as transparent conducting oxide in thin-film solar cells. The experimental findings are discussed in the light of various spin-dependent transport mechanisms known to occur in the respective layers of the pin structure.