Unusual interlayer coupling in layered Cu-based ternary chalcogenides CuMCh2(M=Sb, Bi; Ch=S, Se)

Interlayer interactions play important roles in manipulating the electronic properties of layered semiconductors. One common mechanism is that the valance band maximum (VBM) and the conduction band minimum (CBM) in...

Photon-induced deactivations of multiple traps in CH3NH3PbI3 perovskite films by different photon energies

Two types of electron traps were identified in MAPbI3 perovskite; one can be deactivated by 633 nm and 405 nm illuminations, whereas the other one only by 405 nm illumination. The energy levels of both traps were beneath the conduction band minimum.

Energy Level Engineering of Charge Selective Contact and Halide Perovskite by Modulating Band Offset: Mechanistic Insights

<p>Mixed cation and anion based perovskites solar cells (FAPbI₃)_0.85(MAPbBr₃)_0.15 gave enhanced stability under outdoor conditions, however, it yielded limited power conversion efficiency when SnO₂ and Spiro-OMeTAD were employed as electron and hole transport layer (ETL/HTL). The inevitable interfacial recombination of charge carriers at ETL/perovskite and perovskite/HTL interface diminished the efficiency in planar (n-i-p) perovskite solar cells. Employing computational approach for uni-dimensional device simulator, the effect of band offset on charge recombination at both interfaces were investigated. We noted that it acquired cliff structure when the conduction band minimum of the ETL is lower than that of the perovskite, and thus maximizes interfacial recombination. However, if the conduction band minimum of ETL is higher than perovskite, i.e. spike structure is formed, which improve the performance of solar cell up to an optimum value of conduction band offset allowing to reach performance of 25.21%, with an open circuit voltage (<i>V</i>_oc) of 1231 mV, a current density <i>J</i>_sc of 24.57 mA/cm² and a fill factor of 83.28%. Additionally, we found that beyond the optimum offset value, large spike structure could decrease the performance. With an optimized, energy level of Spiro-OMeTAD and the thickness of mixed-perovskite layer performance of 26.56 % can be attained. Our results demonstrate a detailed understanding about the energy level tuning between the charge selective layers and perovskite and furthermore how the improvement in PV performance can be achieved by adjusting the energy level offset.</p>

Energy Level Engineering of Charge Selective Contact and Halide Perovskite by Modulating Band Offset: Mechanistic Insights

<p>Mixed cation and anion based perovskites solar cells (FAPbI₃)_0.85(MAPbBr₃)_0.15 gave enhanced stability under outdoor conditions, however, it yielded limited power conversion efficiency when SnO₂ and Spiro-OMeTAD were employed as electron and hole transport layer (ETL/HTL). The inevitable interfacial recombination of charge carriers at ETL/perovskite and perovskite/HTL interface diminished the efficiency in planar (n-i-p) perovskite solar cells. Employing computational approach for uni-dimensional device simulator, the effect of band offset on charge recombination at both interfaces were investigated. We noted that it acquired cliff structure when the conduction band minimum of the ETL is lower than that of the perovskite, and thus maximizes interfacial recombination. However, if the conduction band minimum of ETL is higher than perovskite, i.e. spike structure is formed, which improve the performance of solar cell up to an optimum value of conduction band offset allowing to reach performance of 25.21%, with an open circuit voltage (<i>V</i>_oc) of 1231 mV, a current density <i>J</i>_sc of 24.57 mA/cm² and a fill factor of 83.28%. Additionally, we found that beyond the optimum offset value, large spike structure could decrease the performance. With an optimized, energy level of Spiro-OMeTAD and the thickness of mixed-perovskite layer performance of 26.56 % can be attained. Our results demonstrate a detailed understanding about the energy level tuning between the charge selective layers and perovskite and furthermore how the improvement in PV performance can be achieved by adjusting the energy level offset.</p>

Enhancing the ambient stability of few-layer black phosphorus by surface modification

To enhance the ambient stability of black phosphorus, fifteen elements have been selected to investigate their effects on the conduction band minimum of bP.

Designing indirect–direct bandgap transitions in double perovskites

A general design strategy is presented for tuning the convergence of direct and indirect bandgaps based on chemical adjustment of the s- and p-orbital character of the conduction band minimum.

A first-principles study of anionic (S) and cationic (V/Nb) doped Sr2Ta2O7 for visible light photocatalysis

In order to utilize the visible light to catalyze water, UV-active Sr2Ta2O7 is engineered via co-doping of S and V/Nb to shift the valence band maximum upward and conduction band minimum downward by approximately 1 eV, respectively.