[14a-A34-1~7] 13.10 Compound solar cells

[14a-A34-1] Growth and characterization of group-V doped CdTe single crystals by Cd-solvent THM

〇Akira Nagaoka^1,4, Kyu-Bun Han¹, Sudhajit Misra¹, Thomas Wilenski¹, Kenji Yoshino², Yoshitaro Nose³, Michael Scarpulla¹ (1.Univ. of Utah, 2.Miyazaki Univ., 3.Kyoto Univ., 4.JSPS Postdoctoral Fellow for Research Abroad)

Keywords:Compound solar cell, CdTe, II-VI group semiconductor

Cadmium telluride (CdTe) has been well demonstrated as one of the promising photovoltaic material for solar cells because of its near-optimum bandgap of 1.5 eV and its high absorption coefficient, and is the only II-VI group semiconductor that can be relatively easily doped both p and n type conductivity. Recently, power conversion efficiency >22 % was reported for polycrystalline CdTe cells, but further improvements rely on increasing p-type doping while maintaining long minority carrier lifetime. CdTe solar cells using P-doped bulk crystals as the absorber layer and exhibiting open-circuit voltage (V_OC) >1 V has been reported. Combined experimental and theoretical studies indicate that Cd-rich conditions are needed to achieve long carrier lifetime >10 ns by suppressing Te on Cd antisites, but typical bulk crystal growth is carried out either stoichiometriclaly or in Te solvent. For these reasons, it is important to fundamentally understand bulk group-V doping in CdTe under Cd-rich conditions.