Investigations of the structural, optical properties and electronic structure of CdTe1−x Se x films fabricated by RF magnetron sputtering

Se alloying CdTe absorber has attracted much attention for enhancing the short current density (Jsc) of CdTe device with high fill factor (FF) and open circuit voltage (Voc). The structural, morphological, optical properties and electronic structure of co-sputtered CdTe1−xSex films (0 ≤ x ≤ 1) are determined in this study. All CdTe1−xSex films are polycrystalline in nature. Phase transition occurs as x increases. The band gap (Eg) of CdTe1−xSex films can be tuned from 1.35 eV to 1.70 eV. CdTe and CdTe0.838Se0.162 films are p-type but the others are n-type, judging from the relative position of Fermi energy (EF) and the intrinsic Fermi energy (EI). Appropriate electric field can form in Se alloying CdTe absorber with a gradient composition, which enhances carrier collection. The barrier height at the emitter/absorber interface can be designed appropriately by changing the composition of CdTe1−xSex films. These results give reasons why CdTe1−xSex absorber is better than CdTe and device performance can be further improved by optimizing the composition distribution of CdTe1−xSex alloys.