Using porphyrin-amino acid pairs to model the electrochemistry of heme proteins: experimental and theoretical investigations.

Quasi reversibility in electrochemical cycling between different oxidation states of iron is an often seen characteristic of iron containing heme proteins that bind dioxygen. Surprisingly, the system becomes fully reversible in the bare iron-porphyrin complex: hemin. This leads to the speculation that the polypeptide bulk (globin) around the iron-porphyrin active site in these heme proteins is probably responsible for the electrochemical quasi reversibility. To understand the effect of such polypeptide bulk on iron-porphyrin, we study the interaction of specific amino acids with the hemin center in solution. We choose three representative amino acids-histidine (a well-known iron coordinator in bio-inorganic systems), tryptophan (a well-known fluoroprobe for proteins), and cysteine (a redox-active organic molecule). The interactions of these amino acids with hemin are studied using electrochemistry, spectroscopy, and density functional theory. The results indicate that among these three, the interaction of histidine with the iron center is strongest. Further, histidine maintains the electrochemical reversibility of iron. On the other hand, tryptophan and cysteine interact weakly with the iron center but disturb the electrochemical reversibility by contributing their own redox active processes to the system. Put together, this study attempts to understand the molecular interactions that can control electrochemical reversibility in heme proteins. The results obtained here from the three representative amino acids can be scaled up to build a heme-amino acid interaction database that may predict the electrochemical properties of any protein with a defined polypeptide sequence.

Probing the pseudo-1-D ion diffusion in lithium titanium niobate anode for Li-ion battery.

Comprehensive understanding of the charge transport mechanism in the intrinsic structure of an electrode material is essential in accounting for its electrochemical performance. We present here systematic experimental and theoretical investigations of Li(+)-ion diffusion in a novel layered material, viz. lithium titanium niobate. Lithium titanium niobate (exact composition Li0.55K0.45TiNbO5·1.06H2O) is obtained from sol-gel synthesized potassium titanium niobate (KTiNbO5) by an ion-exchange method. The Li(+)-ions are inserted and de-inserted preferentially into the galleries between the octahedral layers formed by edge and corner sharing TiO6 and NbO6 octahedral units and the effective chemical diffusion coefficient, is estimated to be 3.8 × 10(-11) cm(2) s(-1) using the galvanostatic intermittent titration technique (GITT). Calculations based on density functional theory (DFT) strongly confirm the anisotropic Li(+)-ion diffusion in the interlayer galleries and that Li(+)-ions predominantly diffuse along the crystallographic b-direction. The preferential Li(+)-ion diffusion along the b-direction is assisted by line-defects, which are observed to be higher in concentration along the b-direction compared to the a- and c-directions, as revealed by high resolution electron microscopy. The Li-Ti niobate can be cycled to low voltages (≈0.2 V) and show stable and satisfactory battery performance over 100 cycles. Due to the possibility of cycling to low voltages, cyclic voltammetry and X-ray photoelectron spectroscopy convincingly reveal the reversibility of Ti(3+) ↔ Ti(2+) along with Ti(4+) ↔ Ti(3+) and Nb(5+) ↔ Nb(4+).

High proton mobility, solvent induced single crystal to single crystal structural transformation, and related studies on a family of compounds formed from Mn3 oxo-clusters.

The reaction between 4,4'-sulfonyldibenzoic acid (H2SDBA) and manganese under mild conditions resulted in the isolation of two new three-dimensional compounds, [Mn4(C14H8O6S)4(DMA)2]·3DMA, I, and [Mn3(C14H8O6S)3(DMA)2(MeOH)]·DMA, IIa. Both structures have Mn3 trimer oxo cluster units. While the Mn3 oxoclusters are connected through octahedral manganese forming one-dimensional Mn-O-Mn chains in I, the Mn3 units are isolated in IIa. The SDBA units connect the Mn-O-Mn chains and the Mn3 clusters giving rise to the three-dimensional structure. Both compounds have coordinated and free solvent molecules. In IIa, two different solvent molecules are coordinated, of which one solvent can be reversibly exchanged by a variety of other similar solvents via a solvent-mediated single crystal to single crystal (SCSC) transformation. The free lattice DMA solvent molecules in I can be exchanged by water molecules resulting in hydrophilic channels. Proton conductivity studies on I reveals a high proton mobility with conductivity values of ∼0.87 × 10(-3) Ω(-1) cm(-1) at 34 °C and 98% RH, which is comparable to some of the good proton conductivity values observed in inorganic coordination polymers. We have also shown structural transformation of I to IIa through a possible dissolution and recrystallization pathway. In addition, both I and IIa appear to transform to two other manganese compounds [H3O][Mn3(µ3-OH)(C14H8O6S)3(H2O)](DMF)5 and [H3O]2[Mn7(µ3-OH)4(C14H8O6S)6(H2O)4](H2O)2(DMF)8 under suitable reaction conditions. We have partially substituted Co in place of Mn in the Mn3 trimer clusters forming [CoMn2(C14H8O6S)3(DMA)2(EtOH)]·DMA, III, a structure that is closely related to IIa. All the compounds reveal antiferromagnetic behavior. On heating, the cobalt substituted phase (compound III) forms a CoMn2O4 spinel phase with particle sizes in the nanometer range.

Small-angle neutron scattering studies of hemoglobin confined inside silica tubes of varying sizes.

In addition to the chemical nature of the surface, the dimensions of the confining host exert a significant influence on confined protein structures; this results in immense biological implications, especially those concerning the enzymatic activities of the protein. This study probes the structure of hemoglobin (Hb), a model protein, confined inside silica tubes with pore diameters that vary by one order of magnitude (≈20-200 nm). The effect of confinement on the protein structure is probed by comparison with the structure of the protein in solution. Small-angle neutron scattering (SANS), which provides information on protein tertiary and quaternary structures, is employed to study the influence of the tube pore diameter on the structure and configuration of the confined protein in detail. Confinement significantly influences the structural stability of Hb and the structure depends on the Si-tube pore diameter. The high radius of gyration (Rg) and polydispersity of Hb in the 20 nm diameter Si-tube indicates that Hb undergoes a significant amount of aggregation. However, for Si-tube diameters greater or equal to 100 nm, the Rg of Hb is found to be in very close proximity to that obtained from the protein data bank (PDB) reported structure (Rg of native Hb=23.8 Å). This strongly indicates that the protein has a preference for the more native-like non-aggregated state if confined inside tubes of diameter greater or equal to 100 nm. Further insight into the Hb structure is obtained from the distance distribution function, p(r), and ab initio models calculated from the SANS patterns. These also suggest that the Si-tube size is a key parameter for protein stability and structure.

Probing hemoglobin confinement inside submicron silica tubes using synchrotron SAXS and electrochemical response.

The configuration of hemoglobin in solution and confined inside silica nanotubes has been studied using synchrotron small angle X-ray scattering and electrochemical activity. Confinement inside submicron tubes of silica aid in preventing protein aggregation, which is vividly observed for unconfined protein in solution. The radius of gyration (R g) and size polydispersity (p) of confined hemoglobin was found to be lower than that in solution. This was also recently demonstrated in case of confined hemoglobin inside layered polymer capsules. The confined hemoglobin displayed a higher thermal stability with R g and p showing negligible changes in the temperature range 25-75 °C. The differences in configuration between the confined and unconfined protein were reflected in their electrochemical activity. Reversible electrochemical response (from cyclic voltammograms) obtained in case of the confined hemoglobin, in contrary to the observance of only a cathodic response for the unconfined protein, gave direct indication of the differences between the residences of the electroactive heme center in a different orientation compared to that in solution state. The confined Hb showed loss of reversibility only at higher temperatures. The electron transfer coefficient (α) and electron transfer rate constant (k s) were also different, providing additional evidence regarding structural differences between the unconfined and confined states of hemoglobin. Thus, absence of any adverse effects due to confinement of proteins inside the inorganic matrices such as silica nanotubes opens up new prospects for utilizing inorganic matrices as protein "encapsulators", as well as sensors at varying temperatures.

Efficient Rechargeable Li-CO2 Battery with a Liquid Electrolyte-Soluble CuCl2 Electrocatalyst.

We demonstrate here a simple liquid electrolyte soluble Cu-compound, viz., cupric chloride (CuCl2) as an alternative electrocatalyst for nonaqueous Li-CO2 batteries. The key point behind the selection of CuCl2 is that the theoretical potential of Li-CO2 batteries (≈2.8 V; Li+|Li) lies within the Cu1+|Cu0 redox couple (2.3-3.3 V; Li+|Li). The presence of CuCl2 in the liquid electrolyte near to the carbon nanotubes (≡ coelectrocatalyst)-loaded porous-CO2 cathode led to efficient electrocatalysis of CO2 and superior Li-CO2 battery performance. The cell overpotential in the presence of CuCl2 is 0.65 V, which is less than half compared to the one without it (≈1.7 V). Extensive investigations precisely elucidate the electrocatalytic mediation of CuCl2 with the redox characteristics of CO2. Additionally, only in the presence of CuCl2, the existence of Li-oxalate (Li2C2O4) is detected, which is a seldomly reported intermediate preceding the formation of Li2CO3.

Improved lithium cyclability and storage in mesoporous SnO2 electronically wired with very low concentrations (≤1 %) of reduced graphene oxide.

On the wire: Mesoporous tin dioxide (SnO(2)) wired with very low amounts (≤1 %) of reduced graphene oxide (rGO) exhibits a remarkable improvement in lithium-ion battery performance over bare mesoporous or solid nanoparticles of SnO(2). Reversible lithium intercalation into SnO(2)/SnO over several cycles was demonstrated in addition to conventional reversible lithium storage by an alloying reaction.

Shape effect on electronic and photovoltaic properties of CdS nanocrystals.

Changes in electronic and photovoltaic properties of semiconductor nanocrystals predominantly due to changes in shape are discussed here. Cadmium sulfide (CdS) semiconductor nanocrystals of various shapes (tetrapod, tetrahedron, sphere and rod) obtained using an optimized solvothermal process exhibited a mixed cubic (zinc blende) and hexagonal (wurtzite) crystal structure. The simultaneous presence of the two crystal phases in varying amounts is observed to play a pivotal role in determining both the electronic and photovoltaic properties of the CdS nanocrystals. Light to electrical energy conversion efficiencies (measured in two-electrode configuration laboratory solar cells) remarkably decreased by one order in magnitude from tetrapod --> tetrahedron --> sphere --> rod. The tetrapod-CdS nanocrystals, which displayed the highest light to electrical energy conversion efficiency, showed a favorable shift in position of the conduction band edge leading to highest rate of electron injection (from CdS nanocrystal to the wide band gap semiconductor viz. titanium dioxide, TiO2) and lowest rate of electron-hole recombination (higher free electron lifetimes).

Probing the Polysulfide Confinement in Two Different Sulfur Hosts for a Mg|S Battery Employing Operando Raman and Ex-Situ UV-Visible Spectroscopy.

We study here the Mg-polysulfide confinement inside two structurally different model porous materials, viz., toray carbon paper (TC) and multiwalled carbon nanotubes (CNT), using operando Raman and postcycling ex-situ UV-vis spectroscopy. Sulfur encapsulated inside CNT (CNT-S) and TC (TC-S) serves as S-cathodes in a rechargeable room temperature Mg|S battery. Operando Raman spectroscopy indicates the presence of higher-order Mg-polysulfides at the CNT cathode. This is due to the combination of their entrapment inside CNT and also possibly to their localization in the liquid electrolyte in the vicinity of CNT-S. This finding is directly correlated to the ex-situ UV-vis spectroscopy, which shows a lesser degree of Mg-polysulfide dissolution into the electrolyte solution. In comparison, TC-S, where sulfur is encapsulated within the open matrix formed by the nanofiber network of the carbon paper, displays poorer polysulfide confinement. The distinct differences in their abilities to confine the Mg-polysulfides are corroborated by battery performance. In the current density range (0.05-1) C, the battery with CNT-S displays much higher specific capacities, being nearly two times that of TC-S at 1 C.

Probing the Function of a Li-CO2 Battery with a MXene/Graphene Oxide Composite Cathode Electrocatalyst.

We systematically diagnose here the various phases formed at the electrodes in a Li-CO2 battery. The CO2 cathode comprises a mixture of two-dimensional electrocatalysts, MXene and graphene oxide (MXene/GO), configured on Ni foam. The observed overpotential for MXene/GO (2.4 V) is lower than that for GO (2.8 V). MXene/GO also outperforms GO in terms of battery stability and performance. The overall battery reaction (Li2CO3 ↔ Li + CO2) is more efficient in the case of MXene/GO than in the case of GO. This is convincingly demonstrated using ex situ high-resolution synchrotron X-ray diffraction and Raman scattering spectroscopy, which strongly indicates that the MXene/GO composite is more capable than GO in converting Li2CO3 to Li and CO2. When the Li anode is probed, CO2 crossover is evident via the observation of the formation of LiOH/Li2CO3 phases, the proportions of which change during successive cycles.

Transition Metal Phthalocyanines as Redox Mediators in Li-O2 Batteries: A Combined Experimental and Theoretical Study of the Influence of 3d Electrons in Redox Mediation.

Redox mediation is an innovative strategy for ensuring efficient energy harvesting from metal-oxygen systems. This work presents a systematic exploratory analysis of first-row transition-metal phthalocyanines as solution-state redox mediators for lithium-oxygen batteries. Our findings, based on experiment and theory, convincingly demonstrate that d5 (Mn), d7 (Co), and d8 (Ni) configurations function better compared to d6 (Fe) and d9 (Cu) in redox mediation of the discharge step. The d10 configuration (Zn) and non-d analogues (Mg) do not show any redox mediation because of the inability of binding with oxygen. The solution-state discharge product, transition-metal bound Li2O2, undergoes dissociation and oxidation in the charging step of the battery, thus confirming a bifunctional redox mediation. Apart from the reaction pathways predicted based on thermodynamic considerations, density functional theory calculations also reveal interesting effects of electrochemical perturbation on the redox mediation mechanisms and the role of the transition-metal center.

Structure-Redox Response Correlation in a Few Select Heme Systems Using X-ray Absorption Spectroelectrochemistry.

Heme based biomolecules control some of the most crucial life processes, such as oxygen and electron transport during respiration and energy metabolism, respectively. The active site of the heme, viz., the metal center, plays a key role and attributes functionality to these biomolecules. During the oxygen binding and debinding processes, it is important to note that the oxidation state of iron in hemoglobin (+II in the native form) does not undergo any change. However, the spin states of the metal center change. We present here a comprehensive study of the redox response of such molecules, based on the electronic structure of the active site. The local electronic structure of heme in a few selective molecular systems is studied in operando via synchrotron X-ray absorption spectroscopy (Fe K-edge) and cyclic voltammetry. Our objective is to identify the electronic structural parameters that can effectively be correlated with the redox reversibility. Evolution in these parameters can be followed to trace the overall changes in redox state of the system. Our data indicate that axial coordination and spin state of the iron center are two such parameters that are intimately connected with the redox response.

Thermodynamic Insights into Polymorphism-Driven Lithium-Ion Storage in Monoelemental 2D Materials.

Monoelemental two-dimensional materials (borophene, silicene, etc.) are exciting candidates for electrodes in lithium-ion batteries because of their ultralight molar mass. However, these materials' lithium-ion binding mechanism can be complex as the inherited polymorphism may induce phase changes during the charge-discharge cycles. Here, we combine genetic-algorithm-based bottom-up and stochastic top-down structure searching techniques to conduct thermodynamic scrutiny of the lithiated compounds of 2D allotropes of four elements: B, Al, Si, and P. Our first-principles-based high-throughput computations unveil polymorphism-driven lithium-ion binding process and other nonidealities (e.g., bond cleavage, adsorbent phase change, and electroplating), which lacks mention in earlier works. While monolayer B (2479 mAh/g), Al (993 mAh/g), and Si (954 mAh/g) have been demonstrated here as excellent candidates for Li-ion storage, P falls short of the expectation. Our well-designed computational framework, which always searches for lithiated structures at global minima, provides convincing thermodynamical insights and realistic reversible specific-capacity values. This will expectedly open up future experimental efforts to design monoelemental two-dimensional material-based anodes with specific polymorphic structures.

Hemoglobin Dynamics in Solution vis-à-vis Under Confinement: An Electrochemical Perspective.

Confining heme protein in silico often leads to beneficial functionalities such as an enhanced electrochemical response from the heme center. This can be harnessed to design effective biosensors for medical diagnostics. Proteins under confinement, surface confinement on the electrode to be precise, have more ordered and monodisperse structure compared to the protein in bulk solution. As the electrochemical response of a protein comes from those protein molecules that are confined within the electrical double layer across the electrode-electrolyte interface, it is expected that restriction of conformational fluctuations of the polymeric protein will help in enhancement of the electrochemical response. This is probably the prima facie reason for electrochemical response enhancement under confinement. We examine the dynamic features of hemoglobin under confinement vis-à-vis that in bulk solution. We use a variety of spectroscopic techniques across a wide time-space window to establish the following facts: (a) hardening of the protein polypeptide backbone, (b) slowing down of protein diffusion, (c) increase in relaxation times in NMR, and (d) slowing down of dielectric relaxation times under confinement. This indicates an overall quenching of protein dynamics when the protein is confined inside silica matrix. Thus, we hypothesize that along with retention of secondary structure, this quenching of dynamics contributes to the enhancement of electrochemical response observed.

Mutual Diffusivity of an n-Hexane-2,2-Dimethyl Butane Binary Mixture Confined to Zeolite Y.

A molecular dynamic study of a mixture of n-hexane and 2,2-dimethyl butane (22DMB) confined to zeolite NaY has been carried out to understand the distinct diffusivity and mutual diffusivity. Results have been compared with the bulk mixture. For each of these mixtures, eight different runs were employed to compute distinct and mutual diffusivity. From the velocity auto- and cross-correlation functions between n-hexane and n-hexane, n-hexane and 22DMB, 22DMB and 22DMB, the self- and distinct diffusivity of the mixture has been computed. The thermodynamic factor and mutual diffusivity have been calculated. The ratio of D11 to Ds is seen to be 1.11 and 0.75 for the confined mixture, while they are 1.21 and 0.79 for the bulk mixture at 200 and 300 K, respectively.

Probing the Extent of Polysulfide Confinement Using a CoNi2S4 Additive Inside a Sulfur Cathode of a Na/Li-Sulfur Rechargeable Battery.

The extent of confinement of soluble metal polysulfides inside a sulfur cathode strongly determines the performance of metal-sulfur rechargeable batteries. This challenge has been largely tackled by loading sulfur inside various conducting porous scaffolds. However, this approach has not proven to be fully effective because of poor chemical interaction between the scaffold and polysulfides. Here, we demonstrate an excellent strategy of using a sulfide additive in the sulfur cathode, viz., cobalt nickel sulfide (CoNi2S4), to efficiently trap the soluble polysulfides inside the sulfur cathode. In situ Raman and ex situ UV-vis spectroscopies clearly reveal higher retention of polysulfides inside CoNi2S4/S compared to bare sulfur and carbon-sulfur mixture cathodes. Against sodium, the CoNi2S4/S assembly showed remarkable cyclability both as a function of current density (at room temperature) and temperature (at constant current density). The versatility of CoNi2S4 is further proven by the exemplary cyclability at various current densities at room temperature against lithium.

Study of ion transport in lithium perchlorate-succinonitrile plastic crystalline electrolyte via ionic conductivity and in situ cryo-crystallography.

Ion transport mechanism in lithium perchlorate (LiClO(4))-succinonitrile (SN), a prototype of plastic crystalline soft matter electrolyte is discussed in the context of solvent configurational isomerism and ion solvation. Contributions of both solvent configurational isomerism and ion solvation are reflected in the activation energy for ion conduction in 0-1 M LiClO(4)-SN samples. Activation energy due to solvent configurational changes, that is, trans-gauche isomerism is observed to be a function of salt content and decreases in presence of salt (except at high salt concentrations, e.g. 1 M LiClO(4)-SN). The remnant contribution to activation energy is attributed to ion-association. The X-ray diffraction of single crystals obtained using in situ cryo-crystallography confirms directly the observations of the ionic conductivity measurements. Fourier transform infrared spectroscopy and NMR line width measurements provide additional support to our proposition of ion transport in the prototype plastic crystalline electrolyte.

Studying Hemoglobin and a Bare Metal-Porphyrin Complex Immobilized on Functionalized Silicon Surfaces Using Synchrotron X-ray Reflectivity.

We evaluate here, using synchrotron X-ray reflectivity, hemoglobin adsorption characteristics on silicon substrates with varying chemical functionalities. Hemoglobin at isoelectronic point and at negative charge is immobilized on functionalized hydrophilic (hydroxyl, carboxylic, amine) and hydrophobic (alkylated) silicon surfaces for the study. As a control, the bare cofactor hemin (containing only the metal and porphyrin with no amino acid residues) is also studied under similar conditions. Ordered layers (grown using the Langmuir-Blodgett technique) are observed to be less affected by the surface chemistry compared to the multilayers formed by physical absorption. Surface chemistry and charge of the proteins are critical in controlling the protein adsorption characteristics on silicon, such as thickness (correlated to molecule size) and roughness. In this study, this is very well realized by varying both the hydrophobicity and hydrophilicity of the substrate. The fundamental studies discussed here provide us with a set of important guidelines as to how electrode surface functionalization can control molecular conformation/orientation, especially protein adsorption on the substrate. This in turn is expected to have a significant impact on the protein electrochemical function and response of biomolecular devices.

Time-Temperature Scaling and Dielectric Modeling of Conductivity Spectra of Single-Ion Conducting Liquid Dendrimer Electrolytes.

We discuss here the time-temperature scaling and dielectric modeling of the variation of single-ion conductivity with frequency of first generation (G1) liquid dendrimer electrolyte, viz., Poly(propyl ether imine) (PETIM):Li-salt. The PETIM:Li-salt electrolyte exhibits a cation/anion transference number close to unity in the liquid state. On switching from an ester (G1-COOR) to cyano (G1-CN) peripheral group, keeping constant the linker (ether) and branching groups (amine), an interesting transformation from cationic ( t+ ∼1) to anionic conductor ( t- ∼1) takes place. The switch in the nature of the predominant charge carrier is directly related to the change in the magnitude of anion diffusion ( D-), which increases by 1 order of magnitude from D- = 1.1 × 10-12 m2 s-1 (at 30 °C) in G1-COOR to D- = 1.3 × 10-11 m2 s-1 (at 30 °C) in G1-CN. This intriguing ion transport mechanism is probed comprehensively using ac-impedance spectroscopy. The frequency dependent ionic conductivity of G1-CN/G1-COOR, comprised of distinct frequency regimes, is analyzed using the time-temperature superposition scaling principle (TTSP) based on Summerfield and Baranovski scaling methods. To gain insight into the electrical polarization (EP) phenomenon, the relevant frequency regime is converted from conductivity to dielectric versus frequency. The dielectric versus frequency data is modeled using Macdonald and Coelho. The combined approach of TTSP and dielectric modeling provide explicitly the extent of the influence of ion-dendrimer, ion-ion interactions, and also the mobile charge carrier density on the effective ion transport in the homogeneous single-ion conducting dendrimer electrolytes. The combined analysis suggests that ion transport in PETIM-COOR is only due to enhanced ion mobility, whereas in PETIM-CN it is due to both mobile charge carrier concentration and ion mobility. To the best of our knowledge, the scaling and modeling approaches employed here constitute a rare example for validation of such concepts in the context of dendrimer electrolytes.

Planar Heterojunction Solar Cell Employing a Single-Source Precursor Solution-Processed Sb2S3 Thin Film as the Light Absorber.

We discuss here a solution-processed thin film of antimony trisulphide (Sb2S3; band gap ≈ 1.7 eV; electronic configuration: ns2np0) for applications in planar heterojunction (PHJ) solar cells. An alternative solution processing method involving a single-metal organic precursor, viz., metal-butyldithiocarbamic acid complex, is used to grow the thin films of Sb2S3. Because of excess sulphide in the metal complex, the formation of any oxide is nearly retarded. Sb2S3 additionally displays structural anisotropy with a ribbon-like structure along the [001] direction. These ribbon-like structures, if optimally oriented with respect to the electron transport layer (ETL)/glass substrate, can be beneficial for light-harvesting and charge-transport properties. A PHJ solar cell is fabricated comprising Sb2S3 as the light absorber and CdS as an ETL coated on to FTO. With varying film sintering temperature and thickness, the typical ribbon-like structures predominantly with planes hkl: l = 0 stacked horizontally along with respect to CdS/FTO are obtained. The morphology of the films is observed to be a function of the sintering temperature, with higher sintering temperatures yielding compact and smooth films with large-sized grains. Maximum photon to electricity efficiency of 2.38 is obtained for PHJ solar cells comprising 480 nm thick films of Sb2S3 sintered at 350 °C having a grain size of few micrometers (>5 µm). The study convincingly shows that improper grain orientation, which may lead to nonoptimal alignments of the intrinsic structure with regard to the ETL/glass substrate, is not the sole parameter for determining photovoltaics performance. Other solution-processing parameters can still be suitably chosen to generate films with optimum morphology, leading to high photon to electricity efficiency.