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Tantalum-based layered perovskites have always been an interesting topic in photocatalysis, but limited information has been reported in terms of their layer factor. In this work, we have synthesized Dion–Jacobson layered perovskites (A′[An−1TanO3n+1]) of LaTaO4, KLaTa2O7, and KCa2Ta3O10 with n = 1, 2, and 3, respectively. With the modification of 1 wt% Pt co-catalysts, the photocatalytic analysis showed that the performance order of these layered perovskites with different layers is KLaTa2O7 (n = 2) > KCa2Ta3O10 (n = 3) ≫ LaTaO4 (n = 1) with both methanol and NaI as the sacrificial agents. This suggested the importance of interlayer K+ for high photocatalytic performance. We further analyzed the layered perovskites in detail by BET, photoelectrochemical analysis, Mott–Schottky, and VB-XPS test. The combined results indicated that the positions of the conduction band are the dominant factors for the photocatalytic performance of tantalum-based Dion–Jacobson layered perovskites with n = 2 and 3. This work sheds new light on the field of layered perovskites as efficient photocatalysts.

We present a numerical simulation study based on tri-layer double-graded (notch structure) CIGS solar cell. As the In to Ga ratio is an important component for tuning the bandgap, it is important to vary the bandgap and take the advantage in terms of Voc and Jsc. In present simulation, initially, we optimized the CIGS dual absorber layer of bandgap 1.42 eV on top, 1.14 eV in the middle and 1.20 eV in the bottom to form a Notch-like structure of the absorber. Conventional buffer layer of CdS is closely optimum for CIGS with smaller bandgap, but shows poor alignment for higher Ga ratio CIGS absorber with higher bandgap. Ga to In ratio change can lead to two different types of conduction band offsets (CBO), positive CBO leads to “spike” and negative offset results in “cliff”. The optimum spike offset of 0.3 eV is achievable in case of higher bandgap CIGS absorbers using Zn-based buffer layers like Zn1−zMgZO and ZnS. Zn1−zMgzO is the most promising of the three buffer layers and shows the efficiency up to 25.48% under AM 1.5 G illumination.

Layered double hydroxides (LDHs) own admirable potential due to their controllable composition and exchangeable interlayer anions. Herein, pyrenetetrasulfonic acid (PTS) intercalated ZnAl-LDHs (denoted as ZnAl-xPTS, x represents the amount of NaPTS in the starting material) are synthesized by a co-precipitation method, which displays enhanced photocatalytic activity towards the hydroxylation of phenylboric acid to phenol. Various characterizations suggest that PTS plays significant roles in improving the photocatalytic activity: (1) PTS extends the light absorption from UV to visible light region; (2) the introduction of PTS upshifts the conduction band, which is feasible for the formation of O2•−; (3) ZnAl-xPTS produces more free electrons under light irradiation, which leads to greatly improved activity. This study develops an alternative LDHs based photocatalyst for the production of phenol, which also provides an efficient strategy to improve the photocatalytic activity of LDHs.

This chapter serves to widen the student’s understanding beyond textbook examples, by including real-life scenarios that mimic modern day electrochemical systems and considerations, examples include fuel cells, renewable batteries, and solar cells. This chapter therefore aims to provide contextual and hence well-rounded understanding of electrochemical methods and how they relate to current real-world problems and constraints. The combined use of free-response and numerical problems in this chapter will help enhance this understanding.

Conjugated polymer crystals enable us to realize an ideal platform for the highest density-of-state of electrons in valence and conduction bands. Herein we report a facile protocol to prepare cryst...

The effect of Se vacancies on the electronic and transport properties of Mo $$Se_2$$ monolayer is studied using the density functional theory (DFT) and semi-classical Boltzmann transport theory. The calculated results show that the introduction of vacancies in the lattice results in the creation of dangling states in the gap region between conduction band minimum and valance band maximum. As a result, the band gap of the monolayer show decreased values. The transport properties of the monolayer are also greatly affected by the vacancies in the lattice. The power factor of the monolayer show decreased values with the introduction of vacancies in the lattice.

The quasiparticle spectra of atomically thin semiconducting transition metal dichalcogenides (TMDCs) and their response to an ultrafast optical excitation critically depend on interactions with the underlying substrate. Here, we present a comparative time- and angle-resolved photoemission spectroscopy (TR-ARPES) study of the transient electronic structure and ultrafast carrier dynamics in the single- and bilayer TMDCs MoS$_2$ and WS$_2$ on three different substrates: Au(111), Ag(111) and graphene/SiC. The photoexcited quasiparticle bandgaps are observed to vary over the range of 1.9-2.3 eV between our systems. The transient conduction band signals decay on a sub-100 fs timescale on the metals, signifying an efficient removal of photoinduced carriers into the bulk metallic states. On graphene, we instead observe two timescales on the order of 200 fs and 50 ps, respectively, for the conduction band decay in MoS$_2$. These multiple timescales are explained by Auger recombination involving MoS$_2$ and in-gap defect states. In bilayer TMDCs on metals we observe a complex redistribution of excited holes along the valence band that is substantially affected by interactions with the continuum of bulk metallic states., Comment: 10 pages, 4 figures

To improve the efficiency of Cu 2 O top cells, we prepared them with four different n-layers (Ga 2 O 3 , zinc tin oxide, zinc germanium oxide, and ZnO) and correlations between solar parameters and conduction band offset $(\vert \Delta \mathrm{E}_{\mathrm{c}}\vert)$ at the pn junction were investigated. Open-circuit voltage $(\mathrm{V}_{\text{oc}})$ varied greatly depending on the n-layer, and higher $\mathrm{V}_{\text{oc}}$ resulted in higher efficiency. Current density-voltage characteristic curves could be reproduced by device simulations, and $(\vert \Delta \mathrm{E}_{\mathrm{c}}\vert)$ and recombination rate $(\mathrm{S}_{\mathrm{r}})$ at the pn junction in each n-layer were estimated. Both $\vert \Delta \mathrm{E}_{\mathrm{c}}\vert$ and Sr varied greatly depending on the n-layer, and Voc increased $\vert \Delta \mathrm{E}_{\mathrm{c}}\vert$ and $\mathrm{S}_{r}$ decreased.

Double perovskite, Cs2AgBiBr6, is introduced as a lead-free perovskite solar cell. Device modeling of Cs2AgBiBr6 (DP) was accomplished to obtain the optimum parameters using the Solar Cell Capacitance Simulator (SCAPS). Two devices with two different hole transport layers (HTLs) were investigated, including P3HT and Cu2O. For both devices with different HTLs, an optimal thicknesses of 1200 nm and defect densities of $$1.0\times$$ 1014 cm−3 for DP layer were attained. For both HTLs, conduction band offset, CBO, is − 0.21 eV and valence band offset, VBO, is + 0.16 eV. For shallow acceptor doping concentration of P3HT and Cu2O, the values of $$5.0\times {10}^{19}$$ and $$5.0\times {10}^{17}\,{\mathrm{cm}}^{-3}$$ were obtained, respectively. As far as the shallow donor density of electron transport layers (ETLs) is concerned, for both cases, the optimum value of $$5.0\times$$ 1019 cm−3 were achieved. For capture cross section, $${\sigma }_{n,p}$$ , in absorber layer for both HTLs, the optimal value at $${\sigma }_{n,p} \mathrm{of} {10}^{-20}\, {\mathrm{cm}}^{2}$$ for $${N}_{t,DP} ($$ defect density of DP) $$\mathrm{is} {10}^{16} \,{\mathrm{cm}}^{-3}$$ , at $${\sigma }_{n,p} \mathrm{of} {10}^{-19} \,{\mathrm{cm}}^{2}$$ for $${N}_{t,DP}\mathrm{ is} {10}^{15} \,{\mathrm{cm}}^{-3},$$ at $${\sigma }_{n,p} \mathrm{of} {10}^{-18} \,{\mathrm{cm}}^{2}$$ for $${N}_{t,DP}\mathrm{ is} {10}^{14} \,{\mathrm{cm}}^{-3}$$ , at $${\sigma }_{n,p} \mathrm{of} {10}^{-17}\, {\mathrm{cm}}^{2}$$ for $${N}_{t,DP}\mathrm{ is} {10}^{13}\, {\mathrm{cm}}^{-3}$$ , and at $${\sigma }_{n,p} \mathrm{of} {10}^{-16} \,{\mathrm{cm}}^{2}$$ for $${N}_{t,DP}\mathrm{ is} {10}^{12} \,{\mathrm{cm}}^{-3}$$ . For P3HT device, the interface defect density of P3HT/Cs2AgBiBr6 is occurred at 1.0 $$\times$$ 1014 cm−2, and for Cs2AgBiBr6/SnO2 is happened at 1.0 $$\times$$ 109 cm−2. For Cu2O device, the interface defect density of Cu2O/Cs2AgBiBr6 is befallen at 1.0 $$\times$$ 1013 cm−2, and for Cs2AgBiBr6/SnO2 is happened at 1.0 $$\times$$ 1010 cm−2. As for radiative recombination, for P3HT device, the optimal value is happened at 2.3 $$\times$$ 10−13 cm3/s, however, for Cu2O device is occurred at 2.3 $$\times$$ 10−12 cm3/s. Finally, for P3HT device, a maximum power conversion efficiency, PCE, of 11.69% (open-circuit voltage, Voc, of 2.02 V, short-circuit current density, Jsc, of 6.39 mA/cm2, and fill-factor, FF, of 0.90 (90%)) were achieved, and for Cu2O device, a PCE of 11.32% (Voc of 1.97 V, Jsc of 6.39 mA/cm2, and FF of 0.895 (89.5%)) were attained. This is the highest efficiency for Cs2AgBiBr6 double perovskite solar cell which was achieved till now. Finally, our results are providing towards fabricating a lead-free and inorganic solar cell.

The temperature dependence of the resistivity of thin poly(diphenylene phthalide) films in a highly conductive state is studied. A metallic type of conductivity in the range of low temperatures is observed, suggesting the possibility of charge transfer in the films along a narrow conduction band in the band gap.

We compare the contact characteristics for Mo, Pd, and Ti on n-InGaAs layer with a range of active donor concentration from $1.6 \times 10^{18}$ cm−3 to $4.8 \times 10^{19}$ cm−3. The Fermi level pinning of 0.18 eV lower than the bottom of n-InGaAs conduction band is experimentally manifested. It is also revealed that the contact resistivity ( $\rho _{\text {c}}$ ) of Mo/n-InGaAs contact clearly outperforms after annealing. However, for the first time, we demonstrate that the Mo/Pd (2nm)/n-InGaAs contact can achieve a $\rho _{\text {c}}~35$ % and 20% lower than a single Mo/n-InGaAs contact after annealing at 400 °C and 450 °C for 1min, respectively.