The spin-orbit coupling (SOC) field, which is odd function symmetric in k(momentum) and time reversal, at the interface of heterogeneous structures causes Rashba-Dresselhaus (RD) splitting of degenerate bands. The spin-orbit coupling (SOC) field, which is an odd-function (momentum) and time-reversal symmetric dye, at the interface of heterostructures causes Rashba-Dresselhaus (RD) splitting of degenerate bands.
A new perspective on the role of A-site cation for steering Frohlich polaron
- A new perspective on the role of A-site cation for steering Frohlich
- Effects by organic A-site cation versus inorganic A-site cation
- Perovskite solar cells materials containing prospective organic
- Novel inorganic cation N 2 H 5
- Conclusion
The proportion of the cationic component of the A site in the LO mode increases with the introduction of organic cations. We also calculated the imaginary part of the spectral function (Figure 6f) and the bandwidth (Figure 6e).
Rashba-Dresselhaus spin-orbit interactions in LHP interface with graphene
Graphene/CsPbI 3 interface
The displacement of the ferroelectric becomes larger at the interface and becomes larger at the interface. As reported in the LDA+D2 calculation of the previous Gr/tetragonal-MAPbI3, we observe the ferroelectric voltage driven by the attraction between the cation Pb2+ of the PbI2-terminated sheet and graphene. Despite ferroelectric distortion, the C4v point symmetry of the cubic structure is preserved in contrast to the TiO2/MAPbI3 interface described later.
The binding energy (BE) of graphene at PbI2 termination is 20.5 meV/atom, which is 3.3 times larger than that at the CsI termination (Table 2). Large Rashba SOC interaction gives rise to a splitting of the surface band into momentum k and energy E at both the conduction band (CB) and the valence band (VB). While the lowest empty surface state at the PbI2 termination is CBM, the highest occupied surface state is 1 eV less than VBM.
The origin of the unique energy level of Gr/CsPbI3(001) can be explained by observing the shift of the ferroelectric distortion on the surface of CsPbI3. Comparing the relaxed and relaxed CsPbI3 slabs, a significant difference in surface state energy levels is observed. This natural distortion of the ferroelectric surface suggests the origin of the recent observation of Rashba splitting of CsPbBr3 nanocrystals.
TiO 2 /MAPbI 3 interface
If such a barrier exists, the process of electron transport is strongly inhibited and electrons should accumulate at the interface. If a charge recombination process is preferred, it should result in a significant reduction in device performance. However, the presence of the Rashba SOC at the interface (Figure 10 and Table 2) reduces such a recombination process (Figure ??) until the potential barrier is overcome.
Therefore, the presence of the Rashba effect at the interface is important to enhance the electron transfer process at the TiO2/MAPbI3 interface. To clarify the influence of the thermal fluctuations, in addition to the 0 K DFT result, we also investigated RD using the NVT ensemble based on an AIMD simulation around 600 K (in the case of cubic CsPbI3) and 330 K (in the case of cubic MAPbI3). As the main case, we studied the PbI2 termination for Gr/CsPbI3/Gr and the TiO2/MAPbI3 termination.
The results show that the thermal average of the RD distribution is comparable to the 0 K DFT result (Table2). In particular, the configuration of the surface I does not deviate from the 0K configuration even at 330 K due to the fixed MA's orientation (Figure 3b). Therefore, VB has almost the same αRD as 0K DFT and has a small standard deviation of ~0.07 eV ·Å.
Conclusion
Band alignment mechanism of La-doped BaSnO 3 /MAPbI 3 interface
- PBE0-SOC-D3 functional for bulk MAPbI 3 and LBSO
- LBSO/MAPbI 3 interface study
- Conduction band alignment of LBSO/MAPbI 3 with respect to
- Conclusion
In fact, we observe that La doping on BSO shifts the energy of the conduction band and leaves the energy of the valence band intact (Figure 12c). From the density of states (DOS) of LBSO/MAPbI3 at the PBE level, a significant hybridization of the interface atoms is observed regardless of the type of termination. A decrease in the energy level of La is observed in the MAI-SnO2 interface, underlining that it is independent of the CBM energy level.
Given that hybridization is strong in MAPbI3/LBSO, it is important to confirm whether it affects the La electronic state and the conduction band minimum (Sn-s state). The presence of hybridization between the two states results in a significant change in the properties of the conduction band and its energy level. Therefore, it is concluded that the downward shift of the conduction band energy (re-normalization of the band gap) is solely dictated by the electrostatic interaction between the La3+ dopant and the Sn conduction band state.
For the three interfaces, the band alignment of the band edge state as a function of the La x doping concentration (%) is summarized in Fig. 15. In each case, the unwanted alignment of the conduction band between MAPbI3 and BSO can be overcome by a small amount of La-doping. Since LBSO can selectively tune the conduction band energy by La doping, it is possible to control the band energy level only by La doping without substitution with a halide or organic PSC cation.
Proton-mediated band alignment of TiO 2 /MAPbI 3
The short strong hydrogen bonding in TiO 2 /MAPbI 3
We find that these energy differences are much higher than the thermal energy, so we expect the orientational degree of freedom present in the cubic bulk phase to be significantly reduced at the TiO2 interface. Specifically, the C-N axis of the MA is preferentially aligned in such a way that the NH3 group coordinates to the underlying TiO2 by reducing the O· · ·H distance at the interface (Figure 16). Therefore, the [011] orientation, where the NH3 group is completely away from the TiO2 surface, is energetically undesirable, despite being a more favorable orientation in the bulk.
In addition to the DFT results, we performed AIMD calculations with the most stable interface structure (Figure 16c) to fully account for the MA dynamics in the cubic phase (330 K). Most importantly, we confirmed that the O· · · H· · · · N hydrogen bond remains throughout the simulation (15 ps of the last 30 psis used for the equilibrium analysis). In contrast to bulk MAPbI3, the hydrogen bond is not fixed in a particular direction, indicating the presence of ordered MA at the TiO2/MAPbI3 interface (Figure 17).
The binding energy (inset) for the interaction between the TiO2 surface and MA represents an anharmonic potential energy surface that reflects the hidden double-well minima.
Band alignment of TiO 2 /MAPbI 3
Conclusion
One of the deterministic factors for any reaction is the coverage of Habs on the cathode surface. Meanwhile, the Cu layer atoms of the upper layer of the first Cu(1) layer and the second Cu(2) layer in the low energy region (Figure 26) are related to the electronic structure of the system. We briefly discuss the response property and correlation functions, which are naturally related to the concept of Green's function.
The definition of Gis is related to the order of creation (or anhalation) operatordσ(d†σ) on the contour. Thus, depending on the branch (C1 or C2, which is later than C1) and the corresponding order of the time variables, we can define four different Green's functions G(t1, t2). The essential result of the Abrikosov trick is that the mean of any local operator (Q = 1) vanishing in the subspace Q= 0 is proportional to the grand-canonical mean (Q >0) of the same operator[4].
The local Green's function can be derived in different ways, such as the functional derivative ΦLW or the Hamiltonian equation of motion. Here we obtain the local Green's function using the functional derivative of the Luttinger-Ward functional Φ with respect to the bath G, namely the hybridization function ∆. Thus, the spectral function of the impurity or Green's function of residual impurities is no longer equal to the equilibrium impurity NCA G.
Although the derivation of the one-crossing approximation (OCA) had been done on the real-time axis[9], the derivation in the frequency domain is much more desirable. In the course of the derivation, we note that only bath G (or hybridization) has a different time ordering for each pseudo-particle self-energy.
The impurity spectral function A imp β ′ β
Correspondence between equilibrium and non-equilibrium solution at the
Correspondence of pseudo-particle self-energy
Basically, the same procedure is applied to the remaining eigenenergies of the pseudoparticles: Σ>, Correspondence of impurity Green’s function 물질적, 정신적으로 격려와 지도, 조언, 지원을 아낌없이 베풀어 주신 지도교수 김광수 교수님께 깊은 감사의 말씀을 전하고 싶습니다. 교수님의 전폭적인 지원과 의욕 덕분에 보람찬 박사학위를 취득할 수 있었습니다. 교수님의 일대일 지도 덕분에 정말 많은 것을 배웠습니다. 곧 올 수도 있었던 길을 너무 멀리 갔는지 모르겠습니다. 대학원 덕분에 더닝-크루거 효과를 정말 경험했어요. 나의 지식과 능력이 부족함을 확연히 느낀 시절이었습니다. 두 분 덕분에 많이 배웠습니다. 무엇보다도, 나를 키워주시고 평생을 바쳐주신 아버지, 누구보다 이 논문을 기다려주신 할아버지, 남동생 철우와 온 가족에게 이 논문을 바칩니다. 또한 김재형 목사님과 울산 준아래교회 식구들에게도 깊은 감사의 말씀을 전하고 싶습니다.Conclusion
