SPLTRAK Abstract Submission
Understanding the Behavior of Fixed Composition CdSexTe1-x(CST) Solar Cells 
Ebin Bastola1, Adam B. Phillips1, Abasi Abudulium1, Vlad Kornienko2, Manoj K. Jamarkattel1, Zulkifl H. Rabbani1, Jared D. Friedl1, Prabodika N. Kalurachchi1, Ali Abbas2, Abdul Quader1, Xavier Mathew1,3, Michael Walls2, Randy J. Ellingson1, Michael J. Heben1
1Wright Center for Photovoltaics Innovation and Commercialization (PVIC), Department of Physics and Astronomy, University of Toledo, Toledo, OH, United States
/2Centre for Renewable Energy Systems Technology (CREST), Loughborough University, Loughborough, United Kingdom
/3Instituto de Energías Renovables, Universidad Nacional Autónoma de México, Temixco, Mexico

Cadmium selenide (CdSe) plays a vital role to achieving the high short-circuit current density (JSC) and passivating the defects in the absorber layer for CdTe photovoltaics necessary to reach high efficiency. Incorporation of CdSe into devices can be done either by fabricating a CdSe/CdTe bilayer or directly depositing the CdSexTe1-x (CST). While the bilayer results in better device performance, the intrinsic properties of the CST suggest it should be the better absorber material. Here, we fabricated and investigated the structural and opto-electronic properties of fixed composition CST films for varying Se concentrations and report device parameters. The films are produced by leveraging our multisource evaporation chamber, allowing a wide range of Se compositions to be investigated without modification to the system. For fixed compositions CST absorber layers, the minorty carrier lifetime is improved with higher Se content though the grain sizes are slightly smaller for higher Se content. Note that all these samples (pure CdTe and CST) have undergone same CdCl2 treatment. The device efficeincy for fixed compostion CST absorber layer observed is as high as 12.2% while for pure CdTe device (no Se) is 7%. The short circuit current density is high (28 mAcm-2), but CST devices suffer from low open circuit voltage (Voc) and fill factor (FF). For comparison, CdSe/CdTe bilayer devices also fabricated using this system were able to reach efficiency up to 17.7% (VOC 839 mV, JSC 29.0 mAcm-2, FF 72.6%), indicating the system produces good material. We will discuss the material properties of CST and correlate these values to the device performance.