UNIVERSITY OF BUCHAREST
FACULTY OF PHYSICS

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2022-07-01 17:11

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Conference: Bucharest University Faculty of Physics 2019 Meeting


Section: Solid State Physics and Materials Science


Title:
Study of rf-sputtered ZnS and ZnSe thin films for photovoltaic applications


Authors:
Ana-Maria RADUTA(1), Sorina IFTIMIE(1), Veta GHENESCU(2), M. GHENESCU(2), V. A. ANTOHE(1), A. RADU(1), Corina RADU(1), D. MANICA(1), Diana COMAN(1), Luminita DAN(1), Lucian ION(1), Stefan ANTOHE(1,3)


*
Affiliation:
1) University of Bucharest, Faculty of Physics, Bucharest-Magurele,077125, Ilfov, Romania

2) Institute of Space Science, Bucharest-Magurele, 077125, Ilfov, Romania

3) Academy of Romanian Scientists, Bucharest, 030167, Romania


E-mail
ana.raduta@fizica.unibuc.ro


Keywords:
ZnS, ZnSe, CdTe, magnetron-sputtering, AII-BVI semiconductors


Abstract:
Binary compounds such as AII–BVI semiconductors are of great scientific interest due to their excellent optoelectronic properties, especially in thin films based photovoltaic technologies. In this work, polycrystalline ZnS and ZnSe used as windows layers in photovoltaic cells based on CdTe as main absorber, were prepared by RF-magnetron sputtering, and the CdTe films are prepared by thermal vacuum evaporation. The prepared and characterized films were used as component layers into superstrate photovoltaic structures as glass/ZnS/ZnSe/CdTe/Cu:Au. To investigate the structural properties we used X-ray diffraction, which revealed that ZnS, ZnSe and CdTe thin films are pollycristalline with a pronounced (111) texture. It was also observed that after irradiation with protons (3 MeV, 1013 fluency), crystallite sizes decreased while mechanical strains increased. X-ray reflectometry (XRR) was used to evaluate the thickness and the roughness of the films. Morphological investigations of surface of all prepared thin films were made by scanning electron microscopy (SEM) showed relatively smooth surfaces, with compact and uniform aspects and with no drops formed during sputtering processes. The absorption and transmission measurements carried out for all samples deposited onto optical glass were used to the optical bandgap evaluation leading to the values between 2.31-2.7 eV and 3.10-3.65 eV for ZnSe and ZnS thin films, respectively. Furthermore, in Vis-NIR region, transparency is larger than 60% for both ZnSe and ZnS films. Afterwards, the effect of protons (3 MeV, 1013 fluency) irradiation on the physical properties of ZnS/ZnSe/CdTe double-heterojunction photovoltaic structures was discussed.


Acknowledgement:
Support from Executive Unit for Financing Higher Education, Research, Development and Innovation (UEFISCDI) through grant no. 18PCCDI/2018 is acknowledged.