Furthermore, due to the strong photogating effect, these direct-band gap, multi-layer phototransistors produce ultra-high gains of (9.8 +- 2.5) x 10^4 A/W and inferred detectivities of (3.3 +- 0.8) x 10^13 Jones, putting In2Se3 amongst the most sensitive 2D materials for photodetection studied to date..
Source: wiktionary