Protocrystalline Growth of Silicon below 80°C

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Abstract
Protocrystalline silicon deposited at temperatures below 80°C exhibits an extraordinary photosensitivity and superior stability against light-soaking. This material growths at the borderline of the amorphous and nanocrystalline phases in plasma-enhanced chemical vapor deposition. After thermal annealing and subsequent light-soaking, the photosensitivity is comparable to the values after deposition, while amorphous silicon strongly drops off. A structural and optical characterization reveals a small fraction of silicon crystallites embedded in an amorphous well-ordered matrix. We investigate the morphology of silicon films deposited at the edge of crystallinity by the absolute Constant Photocurrent Method and observe a phase transition from amorphous to nanocrystalline silicon. This thickness dependant morphology is of crucial importance for solar cell design. We attain protocrystalline absorber which reflect in a strongly improved fill factor compared to amorphous silicon based solar cells.