Influence of hydrogen radicals treatment on layers and solar cells made of solution-processed amorphous silicon

Solution-processed amorphous silicon is a promising material for semiconductor devices. Unfortunately, its manufacturing leaves a high density of defects in the layer, which can be reduced by a treatment with hydrogen radicals. Here, we present an optimized hydrogen treatment, which is used for best performing solar cells made of solution-processed amorphous silicon. We examine the amount and the nature of hydrogen incorporation using infrared absorption and hydrogen effusion. The hydrogen treatment not only increases hydrogen content significantly, it also enlarges the fraction of hydrogen in a bonding configuration which is known to be advantageous for electronic properties, albeit only close to the surface. Using electron spin resonance and and photothermal deflection spectroscopy spectra, we confirm a reduction of defect density. Regarding the electrical properties, the ratio of photo and dark conductivity is increased by almost two decades. This leads to a greatly enhanced performance of solar cell devices which use the material as the absorber layer. In particular, the efficiency jumps by a factor of three.