NaSbSe2 as a promising light-absorber semiconductor in solar cells: First-principles insights
Chen-Min Dai,
Peng Xu,
Menglin Huang,
Zeng-Hua Cai,
Dan Han,
Yuning Wu,
Shiyou Chen
Affiliations
Chen-Min Dai
State Key Laboratory of Precision Spectroscopy, Key Laboratory of Polar Materials and Devices (MOE), and Department of Optoelectronics, East China Normal University, Shanghai 200241, China
Peng Xu
Research Institute for Magnetoelectronics and Weak Magnetic-field Detection, College of Science, China Three Gorges University, Yichang 443002, China
Menglin Huang
State Key Laboratory of Precision Spectroscopy, Key Laboratory of Polar Materials and Devices (MOE), and Department of Optoelectronics, East China Normal University, Shanghai 200241, China
Zeng-Hua Cai
State Key Laboratory of Precision Spectroscopy, Key Laboratory of Polar Materials and Devices (MOE), and Department of Optoelectronics, East China Normal University, Shanghai 200241, China
Dan Han
State Key Laboratory of Precision Spectroscopy, Key Laboratory of Polar Materials and Devices (MOE), and Department of Optoelectronics, East China Normal University, Shanghai 200241, China
Yuning Wu
State Key Laboratory of Precision Spectroscopy, Key Laboratory of Polar Materials and Devices (MOE), and Department of Optoelectronics, East China Normal University, Shanghai 200241, China
Shiyou Chen
State Key Laboratory of Precision Spectroscopy, Key Laboratory of Polar Materials and Devices (MOE), and Department of Optoelectronics, East China Normal University, Shanghai 200241, China
NaSbSe2 has recently shown great potential to be a light-absorber semiconductor in thin-film solar cells. Our first-principles calculations show that NaSbSe2 has a quasi-direct bandgap (1.11 eV indirect vs 1.18 eV direct gap), which is beneficial for increasing the lifetime of minority carriers. The optical absorption coefficient is high (exceeding 10−4 cm−1 for visible light) because of the direct band-edge transition from the (Sb-5s/5p + Se-4p) valence band to (Sb-5p + Se-4p) conduction band. The formation of the dominant acceptor defects such as NaSb, VNa, and VSb makes it difficult to dope NaSbSe2 to n-type, and thus, only the intrinsic p-type conductivity has been observed. Se-rich conditions are found to produce high concentration of hole carriers and low concentration of recombination-center defects, so we propose that the Se-rich conditions should be adopted for fabricating high efficiency NaSbSe2 solar cells. Furthermore, the mixed-anion NaSb(S,Se)2 alloys are predicted to be highly miscible with a low formation enthalpy and a low miscibility temperature (below room temperature), and their bandgaps can be tuned almost linearly from 1.1 to 1.6 eV, covering the optimal bandgap range for single-junction solar cells. Therefore, we propose that alloying provides a promising method for optimizing the performance of NaSbSe2-based solar cells.
