Polycrystalline silicon (poly-Si) thin films have been widely used in flat panel displays

MEMS(micro-electro-mechanical system) and integrated circuits

and also have great application prospects in other areas such as solar cells and SOP (system on panel). Since there exist grain boundaries (GBs) in poly-Si thin films

the crystal defects and dangling bonds in GB regions would introduce interface states in the band gap. On the one hand

the interface states would trap carriers thus creating barriers against carrier transportation

on the other hand

they could act as effective recombination centers to strengthen the recombination. Therefore

the performance of devices fabricated on poly-Si thin films is generally worse than that on single-crystal silicon thin films. To give a theoretical explanation on the electrical properties of poly-Si thin films under the dark and illumination conditions

various theoretical models have been proposed. In addition

two kinds of ways including analytical method and computer simulation have been developed to determine the energy distribution of interface states in the band gap. This article will briefly review the major research progress in electrical transport theory of poly-Si films and methods for determining the distribution of the interface states

so that researchers engaging in investigation on transport properties of poly-Si thin films or polycrystalline semiconductors could get some reference and inspiration.