Comparative study of Cu(In,Ga)Se2/(PVD)In2S3 and Cu(In,Ga)Se2/(CBD)CdS heterojunction based solar cells by admittance spectroscopy, current–voltage and spectral response measurements

Co-evaporated Cu(In,Ga)Se2 (CIGSe) based solar cells with Physical Vapour Deposited (PVD) Indium Sulphide (In2S3) as buffer layer have been studied by admittance spectroscopy and current-voltage characteristics measurements. The results have been compared to those obtained with a reference CBD-CdS/CIGSe device. In darkness, the PVD-In2S3 buffer layer devices exhibit higher densities of trapping defects and low values of shunt resistance. However, under illumination we have observed an important improvement of the In2S3/CIGSe electronic transport properties. This behavior seems to be linked to the presence of a metastable defect with activation energy of 0.3 eV.