Two-dimensional(2D) layered organic-inorganic hybrid perovskites have attracted much more attention for some applications than their three-dimensional(3D) perovskite counterparts due to their promising thermal and moi...Two-dimensional(2D) layered organic-inorganic hybrid perovskites have attracted much more attention for some applications than their three-dimensional(3D) perovskite counterparts due to their promising thermal and moisture stabilities.In particular, the 2D perovskite devices have shown better promise for optoelectronic applications.However, tunability of optoelectronic properties is often demanded to improve the device performance.Herein, we adopt a newly method to tune the electronic properties of 2D perovskite by introducing pseudohalide into the structure.In this work, we designed a pseudohalidesubstituted 2D perovskite by substituting the out-of-plane halide with pseudohalide and studied the electronic and excitonic properties of 2D-BA2MX4 and 2D-BA2MX2Ps2(M=Ge^(2+), Sn^(2+), and Pb^(2+);X=I;Ps=NCO, NCS, OCN, SCN, Se CN).We revealed the dependence of electronic properties including band gaps, composition of band edges, bonding characteristics, work functions, effective masses, and exciton binding energies on different pseudohalides substituted in 2D perovskite.Our results indicate that the substitution of pseudohalide in 2D perovskites is energetically favorable and can significantly affect the bonding characteristics as well as the CBM and VBM that often play major role in determining their performance in optoelectronic devices.It is expected that the pseudohalide substitution will be helpful in developing more advanced optoelectronic device based on 2D perovskite by optimizing band alignment and promoting charge extraction.展开更多
Metal halide perovskites based on formamidinium(FA),or FA-rich compositions have shown great promise for high-performance photovoltaics.A deeper understanding of the impact of ambient conditions(e.g.,moisture,oxygen,a...Metal halide perovskites based on formamidinium(FA),or FA-rich compositions have shown great promise for high-performance photovoltaics.A deeper understanding of the impact of ambient conditions(e.g.,moisture,oxygen,and illumination)on the possible reactions of FA-based perovskite films and their processing sensitivities has become critical for further advances toward commercialization.Herein,we investigate reactions that take place on the surface of the FA_(0.7)Cs_(0.3),mixed Br/I wide bandgap perovskite thin films in the presence of humid air and ambient illumination.The treatment forms a surface layer containing O,OH,and N-based anions.We propose the latter originates from formamidine trapped at the perovskite/oxide interface reacting further to cyanide and/or formamidinate—an understudied class of pseudohalides that bind to Pb.Optimized treatment conditions improve photoluminescence quantum yield owing to both reduced surface recombination velocity and increased bulk carrier lifetime.The corresponding perovskite solar cells also exhibit improved performance.Identifying these reactions opens possibilities for better utilizing cyanide and amidinate ligands,species that may be expected during vapor processing of FA-based perovskites.Our work also provides new insights into the self-healing or self-passivating of MA-free perovskite compositions where FA and iodide damage could be partially offset by advantageous reaction byproducts.展开更多
In this work, the pseudohalide thiocyanate has been demonstrated as a promising alternative to the halide anion to engineer optoelectronic properties of inorganic/ organic hybrid perovskites because it exhibits better...In this work, the pseudohalide thiocyanate has been demonstrated as a promising alternative to the halide anion to engineer optoelectronic properties of inorganic/ organic hybrid perovskites because it exhibits better chemical stability than the halide anion. Previous reports have suggested that the ionic radii and electronegativity of SCN- is close to that of I^-; the SCN^- doped CH3NH3PbI3 exhibited similar optical properties as pure CH3NH3PbI3. Consequently, it was expected that doping of CsPbBr3 perovskite with SCN^- would result in band gap narrowing. Interestingly, the photoluminescent all-inorganic CsPbBr3 perovskite nanocrystals exhibit an abnormal blue shift in optical properties and improvement of the crystallinity when successfully doped by SCN^-. Combined experimental and theoretical investigations revealed that doping of the CsPbBr3 perovskite with the rod-like SCN^- anion introduced disorder in the crystal lattice, leading to its expansion, and impacted the electronic structure of the perovskite with band gap broadening.展开更多
基金funded by the National Key Research and Development Program of China (2017YFA0204800/2016YFA0202403)the Fundamental Research Funds for the Central Universities (2018CBLZ006)+5 种基金the National Natural Science Foundation of China (61604091 and 61674098)the 111 Project (B14041)the Changjiang Scholar and Innovative Research Team (IRT_14R33)the Chinese National 1000 Talents Plan program (1110010341)the China Postdoctoral Science foundation (2018M633455)the Fundamental Research Funds for the Central Universities (GK201903055)
文摘Two-dimensional(2D) layered organic-inorganic hybrid perovskites have attracted much more attention for some applications than their three-dimensional(3D) perovskite counterparts due to their promising thermal and moisture stabilities.In particular, the 2D perovskite devices have shown better promise for optoelectronic applications.However, tunability of optoelectronic properties is often demanded to improve the device performance.Herein, we adopt a newly method to tune the electronic properties of 2D perovskite by introducing pseudohalide into the structure.In this work, we designed a pseudohalidesubstituted 2D perovskite by substituting the out-of-plane halide with pseudohalide and studied the electronic and excitonic properties of 2D-BA2MX4 and 2D-BA2MX2Ps2(M=Ge^(2+), Sn^(2+), and Pb^(2+);X=I;Ps=NCO, NCS, OCN, SCN, Se CN).We revealed the dependence of electronic properties including band gaps, composition of band edges, bonding characteristics, work functions, effective masses, and exciton binding energies on different pseudohalides substituted in 2D perovskite.Our results indicate that the substitution of pseudohalide in 2D perovskites is energetically favorable and can significantly affect the bonding characteristics as well as the CBM and VBM that often play major role in determining their performance in optoelectronic devices.It is expected that the pseudohalide substitution will be helpful in developing more advanced optoelectronic device based on 2D perovskite by optimizing band alignment and promoting charge extraction.
基金U.S.Department of Energy,Grant/Award Number:DE-AC36-08GO28308Center for Hybrid Organic Inorganic Semiconductors for Energy(CHOISE)National Science Foundation,Grant/Award Number:2043205。
文摘Metal halide perovskites based on formamidinium(FA),or FA-rich compositions have shown great promise for high-performance photovoltaics.A deeper understanding of the impact of ambient conditions(e.g.,moisture,oxygen,and illumination)on the possible reactions of FA-based perovskite films and their processing sensitivities has become critical for further advances toward commercialization.Herein,we investigate reactions that take place on the surface of the FA_(0.7)Cs_(0.3),mixed Br/I wide bandgap perovskite thin films in the presence of humid air and ambient illumination.The treatment forms a surface layer containing O,OH,and N-based anions.We propose the latter originates from formamidine trapped at the perovskite/oxide interface reacting further to cyanide and/or formamidinate—an understudied class of pseudohalides that bind to Pb.Optimized treatment conditions improve photoluminescence quantum yield owing to both reduced surface recombination velocity and increased bulk carrier lifetime.The corresponding perovskite solar cells also exhibit improved performance.Identifying these reactions opens possibilities for better utilizing cyanide and amidinate ligands,species that may be expected during vapor processing of FA-based perovskites.Our work also provides new insights into the self-healing or self-passivating of MA-free perovskite compositions where FA and iodide damage could be partially offset by advantageous reaction byproducts.
基金This work was sponsored by the National Natural Science Foundation of China （Nos. 21475021, 21427807, 61722403, 11404131, and 11674121）, the Natural Science Foundation of Jiangsu Province （No. BK20141331）, the Fundamental Research Funds for the Central Universities, Program for JLU Science and Technology Innovative Research Team, the Special Fund for Talent Exploitation in Jilin Province of China, Jiangsu provincial financial support of fundamental conditions and science and technology for people＇s livelihood for Jiangsu key laboratory of advanced metallic materials （No. BM2007204）.
文摘In this work, the pseudohalide thiocyanate has been demonstrated as a promising alternative to the halide anion to engineer optoelectronic properties of inorganic/ organic hybrid perovskites because it exhibits better chemical stability than the halide anion. Previous reports have suggested that the ionic radii and electronegativity of SCN- is close to that of I^-; the SCN^- doped CH3NH3PbI3 exhibited similar optical properties as pure CH3NH3PbI3. Consequently, it was expected that doping of CsPbBr3 perovskite with SCN^- would result in band gap narrowing. Interestingly, the photoluminescent all-inorganic CsPbBr3 perovskite nanocrystals exhibit an abnormal blue shift in optical properties and improvement of the crystallinity when successfully doped by SCN^-. Combined experimental and theoretical investigations revealed that doping of the CsPbBr3 perovskite with the rod-like SCN^- anion introduced disorder in the crystal lattice, leading to its expansion, and impacted the electronic structure of the perovskite with band gap broadening.
基金supported by the National Key Research and Development Program of China(2021YFA1200700)the National Natural Science Foundation of China(22173019,22033002 and 92056112)the Fundamental Research Funds for the Central Universities(2242022R40072)。
