Presentation Information
[11p-E206-10]Evaluation of BaS Thin Films as a Hole Transport Layer for BaSi2 Solar Cells through Experimental and First-Principles Studies
〇(D)Ammara Firdous1, Koki Hayashi1, Nurfauzi Abdillah1, Yoichiro Koda2, Masami Mesuda2, Kaoru Toko1, Takashi Suemasu1, Hikaru Takashima2 (1.Univ. Tsukuba, 2.Tosoh Corp.)
Keywords:
BaSi2 solar cell,Point defects,hole transport layer (BaS)
his study evaluates barium sulfide (BaS) thin films as a potential hole transport layer (HTL) for barium disilicide (BaSi2) thin-film solar cells. BaSi2 is a promising absorber material due to its high optical absorption coefficient, suitable bandgap (~1.3 eV), and long minority-carrier diffusion length. To improve carrier extraction and reduce parasitic absorption, a PIN-type solar-cell structure incorporating an HTL has been proposed. BaS is considered a suitable HTL candidate because of its wide bandgap and favorable energy-level alignment with BaSi2. BaS thin films were deposited on n+-Si(111) substrates by RF magnetron sputtering at substrate temperatures between 300 and 600 deg.C. Structural, optical, and electronic properties were characterized using GI-XRD, spectroscopic ellipsometry, and UPS, respectively. First-principles calculations were also performed to investigate the electronic structure and defect properties.GI-XRD revealed that highly crystalline polycrystalline rock-salt BaS films were obtained at 475–525 deg.C, with optimum crystallinity at 500 deg.C. Ellipsometry showed an indirect bandgap of approximately 3.6 eV, while UPS measured an ionization potential of 4.3 ± 0.3 eV, close to that of BaSi2 (4.5 eV). Defect calculations identified oxygen interstitials as shallow acceptors capable of promoting p-type conductivity. These results indicate that BaS is a promising HTL candidate for BaSi2 solar cells, and future work will focus on oxygen-incorporated BaS1-xOx thin films to further optimize their electronic properties.