Sb₂S₃:C/CdS p-n junction by laser irradiation

In this paper, we report laser irradiated carbon doping of Sb₂S₃ thin films and formation of a p-n junction photovoltaic structure using these films. A very thin carbon layer was evaporated on to chemical bath deposited Sb₂S₃ thin films of approximately 0.5 μm in thickness. Sb₂S₃ thin films were prepared from a solution containing SbCl₃ and Na₂S₂O₃ at 27 °C for 5 h and the films obtained were highly resistive. These C/Sb₂S₃ thin films were irradiated by an expanded laser beam of diameter approximately 0.5 cm (5 W power, 532 nm Verdi laser), for 2 min at ambient atmosphere. Morphology and composition of these films were analyzed. These films showed p-type conductivity due to carbon diffusion (Sb₂ S₃:C) by the thermal energy generated by the absorption of laser radiation. In addition, these thin films were incorporated in a photovoltaic structure Ag/Sb₂S₃:C/CdS/ITO/Glass. For this, CdS thin film of 50 nm in thickness was deposited on a commercially available ITO coated glass substrate from a chemical bath containing CdCl₂, sodium citrate, NH₄OH and thiourea at 70 °C. On the CdS film, Sb₂S₃/C layers were deposited. This multilayer structure was subjected to the laser irradiation, C/Sb₂S₃ side facing the beam. The p-n junction formed by p-Sb₂S₃:C and n-type CdS showed V_oc = 500 mV and J_sc = 0.5 mA/cm² under illumination by a tungsten halogen lamp. This work opens up a new method to produce solar cell structures by laser assisted material processing.