RESUMEN
A suitable substitution of the lead element in lead-based halide perovskites is a feasible approach to explore lead-free perovskite material with excellent stability, tunable band gap, high optical absorption, and better photovoltaic performance. In this study, the toxic lead is replaced by mixing Ba/Si and Ba/Sn to develop environmentally friendly perovskite materials with excellent properties. MABa0.125Sn0.875I3 has shown evidently improved properties in terms of structural stability and suitable band gap, which indicates that MABa0.125Sn0.875I3 can become the most potential material for applications in single-junction solar cells. Moreover, MABa0.50Sn0.50I3 and MABa0.25Sn0.75I3 can be promising materials for the top cell in the tandem architecture due to their proper band gaps (1.70-1.80 eV). Moreover, the optical absorption coefficients of the proposed lead-free perovskites are stronger than that of MAPbI3 in the range of 500-800 nm. Our work can provide new insights into exploring lead-free perovskite solar cells with excellent stability and suitable band gap.
RESUMEN
The effect of organic cation doping with aziridinium (Az+) on the material properties of CsPbI3 was investigated by applying first-principles calculations. The results showed that the phase stability is greatly improved by incorporating the organic cation Az+ at the A site of CsPbI3. However, the band gap of CsPbI3 is further enlarged from 1.76 to 2.27 eV when 12.5% of Az doping is used. The optical absorption coefficient of Cs0.875Az0.125PbI3 is also decreased in the visible light region. The reasons of the improved phase stability and the enlargement of band gap arising from the organic cation doping are revealed. Our calculated results can provide theoretical guidance for improving the phase stability of halide perovskites.
RESUMEN
Organic-inorganic hybrid perovskites have attracted extensive attention as promising photovoltiac materials for high-efficiency solar cells. In this study, strain effects on the material properties of Ge-based perovskites are fully investigated by the first-principles calculations. The results indicate that the structural, mechanical, electronic and optical properties of CH3NH3GeX3 (X = Cl, Br, I) are sensitive to external modulations. The band gaps of three Ge-based halide perovskites are well predicted by using the HSE06 functional. By increasing the compressive strain, the band gaps of three compounds decrease. A suitable band gap (1.36 eV) of CH3NH3GeI3 can be obtained under a strain of -3%. Moreover, the calculated elastic constants further imply that this compound is stable under this condition. The relationship between the band gap variation and geometry change under the compressive strain is revealed. These results are useful for understanding the effects of strain on the material properties of semiconductors and guiding the experiments to improve photovoltaic performance of Ge-based perovskites.
RESUMEN
In recent years, double perovskites have attracted considerable attention as potential candidates for photovoltaic applications. However, most double perovskites are not suitable for single-junction solar cells due to their large band gaps (over 2.0 eV). In the present study, we have investigated the structural, mechanical, electronic and optical properties of the Cs2Te1-x Ti x I6 solid solutions using first-principles calculations based on density functional theory. These compounds exhibit good structural stability compared to CH3NH3PbI3. The results suggest that Cs2TeI6 is an indirect band gap semiconductor, and it can become a direct band gap semiconductor with the value of 1.09 eV when the doping concentration of Ti4+ is 0.50. Moreover, an ideal direct band gap of 1.31 eV is obtained for Cs2Te0.75Ti0.25I6. The calculated results indicate that all the structures are ductile materials except for Cs2Te0.50Ti0.50I6. Our results also show that these materials possess large absorption coefficients in the visible light region. Our work can provide a route to explore stable, environmentally friendly and high-efficiency light absorbers for use in optoelectronic applications.