Tuning of the electronic bandgap of SnSe compound by oxygen and sulphur doping and their optical characteristics for solar cell applications oleh Muhammad Waqas Iqbal, Mumtaz Manzoor, Mohsan Yaqub, N.A. Noor, Taswar Abbas, Ramesh Sharma, Shaimaa A.M. Abdelmohsen, Ahmed Z. Dewidar