Analysis of a-Si:H p-i-n photodiode detection of HeLa cells luminescence

Today, optical biosensors are the most promising candidates for Lab-on-a-Chip (LoC) with regards to their sensitivity and miniaturization. The label-free optical detection method has a low negative influence on tissue and is therefore suitable for the detection of mammalian cells and the molecule itself. The attractive optical methods for analyte detection, chemiluminescence and fluorescence, require a highly sensitive photodetector as biotransducer. In addition, the optoelectronic technology provides the thin film hydrogenated amorphous silicon (a-Si:H) photodiodes integration in microfluidic systems. In our previous work we have observed the influence of the density of native and light-induced localized states, distributed in the mobility gap of aSi: H at different bias voltages, on the detection of luminescence of HeLa cells. As in the optical bias dependence of the modulated photocurrent method (OBMPC), the sample is excited by a blue LED light bias beam of constant intensity, to activates the dangling bonds in a-Si:H and induces a second light beam carried out from the chemiluminescent emission reaction in HeLa cells. The analysis of recombination rate and space charge density in a- Si:H is performed to better understand the underlying physics for luminescence detection at applied different bias voltages on the photodiode.