Highly Stable Colloidal “Giant” Quantum Dots Sensitized Solar Cells

Colloidal quantum dots (QDs) are widely studied due to their promising optoelectronic properties. This study explores the application of specially designed and synthesized “giant” core/shell CdSe/(CdS)_x QDs with variable CdS shell thickness, while keeping the core size at 1.65 nm, as a highly efficient and stable light harvester for QD sensitized solar cells (QDSCs). The comparative study demonstrates that the photovoltaic performance of QDSCs can be significantly enhanced by optimizing the CdS shell thickness. The highest photoconversion efficiency (PCE) of 3.01% is obtained at optimum CdS shell thickness ≈1.96 nm. To further improve the PCE and fully highlight the effect of core/shell QDs interface engineering, a CdSe_x S_1?x interfacial alloyed layer is introduced between CdSe core and CdS shell. The resulting alloyed CdSe/(CdSe_x S_1?x )₅/(CdS)₁ core/shell QD‐based QDSCs yield a maximum PCE of 6.86%, thanks to favorable stepwise electronic band alignment and improved electron transfer rate with the incorporation of CdSe_x S_1?x interfacial layer with respect to CdSe/(CdS)₆ core/shell. In addition, QDSCs based on “giant” core/CdS‐shell or alloyed core/shell QDs exhibit excellent long‐term stability with respect to bare CdSe‐based QDSCs. The giant core/shell QDs interface engineering methodology offers a new path to improve PCE and the long‐term stability of liquid junction QDSCs.     

Highly Efficient Quantum‐Dot‐Sensitized Solar Cell Based on Co‐Sensitization of CdS/CdSe

Cadmium sulfide (CdS) and cadmium selenide (CdSe) quantum dots (QDs) are sequentially assembled onto a nanocrystalline TiO₂ film to prepare a CdS/CdSe co‐sensitized photoelectrode for QD‐sensitized solar cell application. The results show that CdS and CdSe QDs have a complementary effect in the light harvest and the performance of a QDs co‐sensitized solar cell is strongly dependent on the order of CdS and CdSe respected to the TiO₂. In the cascade structure of TiO₂/CdS/CdSe electrode, the re‐organization of energy levels between CdS and CdSe forms a stepwise structure of band‐edge levels which is advantageous to the electron injection and hole‐recovery of CdS and CdSe QDs. An energy conversion efficiency of 4.22% is achieved using a TiO₂/CdS/CdSe/ZnS electrode, under the illumination of one sun (AM1.5,100 mW cm^?2). This efficiency is relatively higher than other QD‐sensitized solar cells previously reported in the literature.     

Multistage Coloring Electrochromic Device Based on TiO2 Nanotube Arrays Modified with WO3 Nanoparticles

WO₃ nanoparticles loaded in TiO₂ nanotube arrays, fabricated by a chemical bath deposition (CBD) technique in combination with a pyrolysis process, is uniform and the diameter can be easily adjusted by the deposition times. The resultant hybrid nanotubes array shows a multistage coloring electrochromic response at different potential bias. The formation of a 3‐dimensional WO₃/TiO₂ junction promotes unidirectional charge transport due to the one‐dimensional features of the tubes, which leads to the significant positive‐shift onset potential of the cathodic reaction (ion insertion) and the highly increased proton storage capacity. Compared to non‐decorated nanotube arrays, the enhanced electrochromic properties of longer lifetime, higher contrast ratio (bleaching time/coloration time), and improved tailored electrochromic behavior could be achieved using the composite films.     

Synergistic Interaction of Dyes and Semiconductor Quantum Dots for Advanced Cascade Cosensitized Solar Cells

A new procedure for the cosensitization with quantum dots (QDs) and dyes for sensitized solar cells is reported here. Cascade cosensitization of TiO₂ electrodes is obtained by the sensitization with CdS QDs and zinc phthalocyanines (ZnPcs), in which ZnPcs containing a sulfur atom are specially designed to produce a cascade injection by direct attachment to QDs. This strategy causes a double synergetic interaction. This is the differentiating point of cascade cosensitization in comparison with other approaches in which dyes with conventional functionalization are anchored to TiO₂ electrodes. Cosensitization produces a panchromatic response from the visible to near‐IR region already observed with other sensitization strategies. However, cascade cosensitization produces in addition a synergistic interaction between QDs and dye, that it is not merely limited to the complementary light absorption, but dye enhances the efficiency of QD sensitization acting as a passivating agent. The cascade cosensitization concept is demonstrated with using [Co(phen)₃]^3+/2+ redox electrolyte. The TiO₂/CdS QD‐ZnPc/[Co(phen)₃]^3+/2+ sensitized solar cell shows a large improvement of short‐circuit photocurrent and open‐circuit voltage in comparison with samples just sensitized with QDs. The advent of such cosensitized QD‐ZnPc solar cells paves the way to extend the absorbance region of the promising QD‐based solar cells and the development of a new family of molecules designed for this purpose.     

多晶MAPbBr_(3)薄膜中束缚载流子热发射复合过程北大核心CSCD

有机-无机卤化铅钙钛矿(organic inorganic lead halide perovskite,OLHP)半导体材料内部的陷阱是影响OLHP的光电性能的重要因素。为了理解多晶的甲胺溴基钙钛矿((Methylammonium)PbBr_(3),MAPbBr_(3))薄膜中陷阱对光生载流子复合的影响,本文采用了时间分辨微波光电导(time resolved microwave conductivity,TRMC)技术探究了多晶MAPbBr_(3)薄膜的光生载流子复合动力学过程。实验测量结果表明多晶MAPbBr_(3)薄膜的载流子复合过程包括自由载流子复合与束缚载流子的热发射复合两部分。其中,与束缚载流子热发射复合相关的能级远离连续带,且对应的能级深度约为0.6 eV,分布宽度约为89.2 meV。本文同时利用变激发波长TRMC对比实验,分析浅束缚光生电子与导带光生电子复合过程的差异。相比于导带上的电子,实验结果表明浅束缚电子跃迁到深束缚能级的概率更大。     

Plasmonic Heterostructure TiO2‐MCs/WO3−x‐NWs with Continuous Photoelectron Injection Boosting Hot Electron for Methane Generation

Nonmetallic plasmonic heterostructure TiO₂‐mesocrystals/WO_3?x‐nanowires (TiO₂‐MCs/WO_3?x‐NWs) are constructed by coupling mesoporous crystal TiO₂ and plasmonic WO_3?x through a solvothermal procedure. The continuous photoelectron injection from TiO₂ stabilizes the free carrier density and leads to strong surface plasmon resonance (SPR) of WO_3?x, resulting in strong light absorption in the visible and near‐infrared region. Photocatalytic hydrogen generation of TiO₂‐MCs/WO_3?x‐NWs is attributed to plasmonic hot electrons excited on WO_3?x‐NWs under visible light irradiation. However, utilization of injected photoelectrons on WO_3?x‐NWs has low efficiency for hydrogen generation and a co‐catalyst (Pt) is necessary. TiO₂‐MCs/WO_3?x‐NWs are used as co‐catalyst free plasmonic photocatalysts for CO₂ reduction, which exhibit much higher activity (16.3 µmol g^?1 h^?1) and selectivity (83%) than TiO₂‐MCs (3.5 µmol g^?1 h^?1, 42%) and WO_3?x‐NWs (8.0 µmol g^?1 h^?1, 64%) for methane generation under UV–vis light irradiation. A photoluminescence study demonstrates the photoelectron injection from TiO₂ to WO_3?x, and the nonmetallic SPR of WO_3?x plays a great role in the highly selective methane generation during CO₂ photoreduction.     

Capacitance Enhancement in a Semiconductor Nanostructure‐Based Supercapacitor by Solar Light and a Self‐Powered Supercapacitor–Photodetector System

The effects of the environment on the energy storage of supercapacitors as well as the underlying mechanisms have long been neglected. This paper reports that the capacitance of hexagonal‐phase tungsten oxide (h‐WO₃)‐based supercapacitors increases by ≈17% under solar light. Thorough analyses of the wavelength dependence of the enhancement, capacitive mechanism, energy storage dynamics, and impedance reveal that: i) photoexcited electrons are responsible for the enhancement; ii) the insertion of protons into the large hexagonal tunnels of h‐WO₃, instead of a surface capacitive process, is greatly facilitated by the photoexcited electrons; iii) the theoretical light‐induced capacitance enhancement can reach up to 38% for a h‐WO₃‐based supercapacitor. Moreover, as an application of this finding, a self‐powered photodetector based on a h‐WO₃ supercapacitor is fabricated, wherein the photoexcited electrons serve as the signal for detecting solar light. The device works without an external power source and can be considered as an ultimately integrated power source–sensor system. This work sheds light on the interaction between solar light and a semiconductor‐based supercapacitor as well as the concrete mechanisms behind the phenomenon. These efforts also open the door to the design of highly integrated, brand‐new power source–sensor systems.     

Formation and Control of Ultrasharp Metal/Molecule Interfaces by Controlled Immobilization of Size‐Selected Metal Nanoclusters onto Organic Molecular Films

The formation of metallic layers on ultrathin molecular films via a well‐controlled interface is essential for constructing organic nanodevices composed of metal/molecule/metal sandwich junctions. The scanning tunneling microscopy and spectroscopy studies demonstrate that an ultrasharp metal/molecule interface is realizable by depositing size‐selected Ag nanoclusters (Ag_n) from the gas phase on few‐layer films of C₆₀ molecules. It is also demonstrated that Ag_n nanoclusters can be immobilized on monolayer films of oligothiophene molecules via C₆₀ molecules, although they three‐dimensionally aggregate on bare oligothiophene films. It is also shown that electrons and holes are injected into the topmost layer of C₆₀ films via the Ag_n/C₆₀ interface. Moreover, the barrier height for carrier injection at the Ag_n/C₆₀ interface can be modified depending on the size of Ag_n nanoclusters and the kinetic energy during the deposition. The present results demonstrate that the controlled immobilization of metallic nanoclusters on molecular films can be used as a fabrication technology for metal/molecule/metal junctions.     

Hydrothermal synthesis of WO3 films on the TiO2 substrates and their photochromic properties

Tungsten oxide (WO₃) films have been prepared on the synthesized TiO₂ substrates from a sodium tungsten precursor via a hydrothermal method. X-ray diffraction, scanning electron microscopy and transmission electron microscopy analyses were used to investigate the effect of precursor concentrations on the structures and morphologies of the films. Ordered WO₃ films were successfully synthesized on the as-grown TiO₂ substrates. With the concentrations increasing from 0.001 M to 0.024 M, the morphologies of the films changed from multi-layer laminated structure to ladder-shaped lamellar structure finally columnar structure. The results also showed that with an increase in precursor concentration, the observed absorptions at 365 nm of the films increased until precursor concentration of 0.016 M, and then decreased with higher concentration. The film obtained with precursor concentration of 0.016 M on the TiO₂ substrate had the best photochromic properties.     

PbS and CdS Quantum Dot‐Sensitized Solid‐State Solar Cells: “Old Concepts,New Results”

Lead sulfide (PbS) and cadmium sulfide (CdS) quantum dots (QDs) are prepared over mesoporous TiO₂ films by a successive ionic layer adsorption and reaction (SILAR) process. These QDs are exploited as a sensitizer in solid‐state solar cells with 2,2′,7,7′‐tetrakis(N,N‐di‐p‐methoxyphenylamine)‐9,9′‐spirobifluorene (spiro‐OMeTAD) as a hole conductor. High‐resolution transmission electron microscopy (TEM) images reveal that PbS QDs of around 3 nm in size are distributed homogeneously over the TiO₂ surface and are well separated from each other if prepared under common SILAR deposition conditions. The pore size of the TiO₂ films and the deposition medium are found to be very critical in determining the overall performance of the solid‐state QD cells. By incorporating promising inorganic QDs (PbS) and an organic hole conductor spiro‐OMeTAD into the solid‐state cells, it is possible to attain an efficiency of over 1% for PbS‐sensitized solid‐state cells after some optimizations. The optimized deposition cycle of the SILAR process for PbS QDs has also been confirmed by transient spectroscopic studies on the hole generation of spiro‐OMeTAD. In addition, it is established that the PbS QD layer plays a role in mediating the interfacial recombination between the spiro‐OMeTAD⁺ cation and the TiO₂ conduction band electron, and that the lifetime of these species can change by around 2 orders of magnitude by varying the number of SILAR cycles used. When a near infrared (NIR)‐absorbing zinc carboxyphthalocyanine dye (TT1) is added on top of the PbS‐sensitized electrode to obtain a panchromatic response, two signals from each component are observed, which results in an improved efficiency. In particular, when a CdS‐sensitized electrode is first prepared, and then co‐sensitized with a squarine dye (SQ1), the resulting color change is clearly an addition of each component and the overall efficiencies are also added in a more synergistic way than those in PbS/TT1‐modified cells because of favorable charge‐transfer energetics.     

Photosensitization of TiO2 Nanostructures with CdS Quantum Dots: Particulate versus Tubular Support Architectures

TiO₂ nanotube arrays and particulate films are modified with CdS quantum dots with an aim to tune the response of the photoelectrochemical cell in the visible region. The method of successive ionic layer adsorption and reaction facilitates size control of CdS quantum dots. These CdS nanocrystals, upon excitation with visible light, inject electrons into the TiO₂ nanotubes and particles and thus enable their use as photosensitive electrodes. Maximum incident photon to charge carrier efficiency (IPCE) values of 55% and 26% are observed for CdS sensitized TiO₂ nanotube and nanoparticulate architectures respectively. The nearly doubling of IPCE observed with the TiO₂ nanotube architecture is attributed to the increased efficiency of charge separation and transport of electrons.     

The influence of metal overlayers on electrochromic behavior of Wo3 films

Metallic overlayers have been deposited on vapor-deposited WO₃ to control the kinetics of coloration and bleaching in a WO₃-liquid electrolyte electrochromic cell. These over-layers, when porous, have been found to increase the rate of coloration/bleaching and the proton transfer rate at the WO₃-electrolyte interface, when appropriate voltages were applied. This effect has been characterized with potentio-static and galvanostatic measurements and compared to the coloration and bleaching of WO₃ (without metallic overlayers). Coloration of WO₃ films is influenced at short times by resistance and electric field effects, in disagreement with the general assumption of high conductivity in vapor-deposited WO₃. The rate of coloration was also influenced by mixed barriers at the WO₃-electrolyte interface. The barriers consist of a Schottky barrier at the WO₃ surface and a Helm-holtz double layer. The coloration and bleaching mechanisms for WO₃ with overlayers have been discussed based upon dif-fusion of electrons through the WO₃, WO₃-overlayer interface, or the SnO₂-WO₃ interface, and proton diffusion at the WO₃-electrolyte interface. Resistance effects in the WO₃ were found to be reduced by the overlayer. Electron injection in WO₃ occurred both at the SnO₂ and the overlayer inter-faces, thus increasing the rate of proton transfer, and the rate of coloration/bleaching. A part of this work was presented at EMC, Boulder, CO, B9, June 27, 1979.     

Electrostatic Self‐Assembly of Nanosized Carbon Nitride Nanosheet onto a Zirconium Metal–Organic Framework for Enhanced Photocatalytic CO2 Reduction

UiO‐66, a zirconium based metal–organic framework, is incorporated with nanosized carbon nitride nanosheets via a facile electrostatic self‐assembly method. This hybrid structure exhibits a large surface area and strong CO₂ capture ability due to the introduction of UiO‐66. We demonstrate that electrons from the photoexcited carbon nitride nanosheet can transfer to UiO‐66, which can substantially suppress electron–hole pair recombination in the carbon nitride nanosheet, as well as supply long‐lived electrons for the reduction of CO₂ molecules that are adsorbed in UiO‐66. As a result, the UiO‐66/carbon nitride nanosheet heterogeneous photocatalyst exhibits a much higher photocatalytic activity for the CO₂ conversion than that of bare carbon nitride nanosheets. We believe this self‐assembly method can be extended to other carbon nitride nanosheet loaded materials.     

Low Roll‐Off Perovskite Quantum Dot Light‐Emitting Diodes Achieved by Augmenting Hole Mobility

The external quantum efficiencies (EQEs) of perovskite quantum dot light‐emitting diodes (QD‐LEDs) are close to the out‐coupling efficiency limitation. However, these high‐performance QD‐LEDs still suffer from a serious issue of efficiency roll‐off at high current density. More injected carriers produce photons less efficiently, strongly suggesting the variation of ratio between radiative and non‐radiative recombination. An approach is proposed to balance the carrier distribution and achieve high EQE at high current density. The average interdot distance between QDs is reduced and this facilitates carrier transport in QD films and thus electrons and holes have a balanced distribution in QD layers. Such encouraging results augment the proportion of radiative recombination, make devices with peak EQE of 12.7%, and present a great device performance at high current density with an EQE roll‐off of 11% at 500 mA cm^?2 (the lowest roll‐off known so far) where the EQE is still over 11%.     

Evidence and Effect of Photogenerated Charge Transfer for Enhanced Photocatalysis in WO3/TiO2 Heterojunction Films: A Computational and Experimental Study

Semiconductor heterojunctions are used in a wide range of applications including catalysis, sensors, and solar‐to‐chemical energy conversion devices. These materials can spatially separate photogenerated charge across the heterojunction boundary, inhibiting recombination processes and synergistically enhancing their performance beyond the individual components. In this work, the WO₃/TiO₂ heterojunction grown by chemical vapor deposition is investigated. This consists of a highly nanostructured WO₃ layer of vertically aligned nanorods that is then coated with a conformal layer of TiO₂. This heterojunction shows an unusual electron transfer process, where photogenerated electrons move from the WO₃ layer into TiO₂. State‐of‐the‐art hybrid density functional theory and hard X‐ray photoelectron spectroscopy are used to elucidate the electronic interaction at the WO₃/TiO₂ interface. Transient absorption spectroscopy shows that recombination is substantially reduced, extending both the lifetime and population of photogenerated charges into timescales relevant to most photocatalytic processes. This increases the photocatalytic efficiency of the material, which is among the highest ever reported for a thin film. In allying computational and experimental methods, this is believed to be an ideal strategy for determining the band alignment in metal oxide heterojunction systems.     

Improved Hydrogen Production of Au–Pt–CdS Hetero‐Nanostructures by Efficient Plasmon‐Induced Multipathway Electron Transfer

The design of new functional materials with excellent hydrogen production activity under visible‐light irradiation has critical significance for solving the energy crisis. A well‐controlled synthesis strategy is developed to prepare an Au–Pt–CdS hetero‐nanostructure, in which each component of Au, Pt, and CdS has direct contact with the other two materials; Pt is on the tips and a CdS layer along the sides of an Au nanotriangle (NT), which exhibits excellent photocatalytic activity for hydrogen production under light irradiation (λ > 420 nm). The sequential growth and surfactant‐dependent deposition produce the three‐component Au–Pt–CdS hybrids with the Au NT acting as core while Pt and CdS serve as a co‐shell. Due to the presence of the Au NT cores, the Au–Pt–CdS nanostructures possess highly enhanced light‐harvesting and strong local‐electric‐field enhancement. Moreover, the intimate and multi‐interface contact generates multiple electron‐transfer pathways (Au to CdS, CdS to Pt and Au to Pt) which guide photoexcited electrons to the co‐catalyst Pt for an efficient hydrogen reduction reaction. By evaluating the hydrogen production rate when aqueous Na₂SO₃–Na₂S solution is used as sacrificial agent, the Au–Pt–CdS hybrid exhibits excellent photocatalytic activity that is about 2.5 and 1.4 times larger than those of CdS/Pt and Au@CdS/Pt, respectively.     

Spray‐Coated Colloidal Perovskite Quantum Dot Films for Highly Efficient Solar Cells

A fully automated spray‐coated technology with ultrathin‐film purification is exploited for the commercial large‐scale solution‐based processing of colloidal inorganic perovskite CsPbI₃ quantum dot (QD) films toward solar cells. This process is in the air outside the glove box. To further improve the performance of QD solar cells, the short‐chain ligand of phenyltrimethylammonium bromide (PTABr) with a benzene group is introduced to partially substitute for the original long‐chain ligands of the colloidal QD surface (namely PTABr‐CsPbI₃). This process not only enhances the carrier charge mobility within the QD film due to shortening length between adjacent QDs, but also passivates the halide vacancy defects of QD by Br^? from PTABr. The colloidal QD solar cells show a power conversion efficiency (PCE) of 11.2% with an open voltage of 1.11 V, a short current density of 14.4 mA cm^?2, and a fill factor of 0.70. Due to the hydrophobic surface chemistry of the PTABr–CsPbI₃ film, the solar cell can maintain 80% of the initial PCE in ambient conditions for one month without any encapsulation. Such a low‐cost and efficient spray‐coating technology also offers an avenue to the film fabrication of colloidal nanocrystals for electronic devices.     

Macroscopic Nanotemplating of Semiconductor Films with Hydrogen‐Bonded Lyotropic Liquid Crystals

Aqueous gel‐like lyotropic liquid crystals with extensive hydrogen bonding and nanoscale hydrophilic compartments have been used to define the growth of macroscopic nanotemplated CdS and CdTe thin films. These mesoporous semiconductor films contain a hexagonal array of 2.5 nm pores, 7 nm center‐to‐center, that extend in an aligned fashion perpendicular to the substrate. The CdS is deposited on a polypropylene substrate by a reaction between Cd(NO₃)₂ dissolved in the liquid crystal and H₂S transported via diffusion through the substrate. The CdTe is electrodeposited on indium‐tin‐oxide‐coated glass from TeO₂ and Cd(NO₃)₂, both of which are dissolved in the liquid‐crystal template. The porous nature of the CdTe films enables chemical transformations of the entire bulk of the film. As electrodeposited, the CdTe films are Te rich and, in contrast to a non‐templated film, the excess Te could be removed via a chemical treatment, proving the continuity of the pores in the nanotemplated films. These results suggest that liquid‐crystal lithography with hydrogen‐bonding amphiphiles may be a useful approach to create materials with nanoscale features over macroscopic dimensions.     

WO3/NiWO4复合薄膜的制备及其光电化学性能

采用两步水热法在导电玻璃(FTO)上制备了WO₃/NiWO₄复合薄膜。通过XRD,SEM表征了WO₃/NiWO₄复合薄膜的组成结构及微观形貌,利用UV-Vis、光电流测试、光电催化测试和交流阻抗测试分析了WO₃/NiWO₄复合薄膜的光电性能。结果表明:WO₃/NiWO₄复合薄膜相较于WO₃薄膜具有更好的光吸收特性、光电流密度和光电催化活性,其中水热反应3h的WO₃/NiWO₄复合薄膜的光电化学性能最佳。WO₃/NiWO₄-3h在1.4V(vs.Ag/AgCl)时的光电流密度为1.94mA/cm²,光电催化210min对亚甲基蓝溶液的降解效率为57.1%。交流阻抗图谱表明WO₃/NiWO₄薄膜的电荷转移电阻小于WO₃薄膜,光电化学性能更优。     

Solar Cells with Enhanced Photocurrent Efficiencies Using Oligoaniline‐Crosslinked Au/CdS Nanoparticles Arrays on Electrodes

Different configurations of CdS nanoparticles (NPs) are linked to Au electrodes by electropolymerization of thioaniline‐functionalized CdS NPs onto thioaniline‐functionalized Au‐electrodes. In one configuration, thioaniline‐functionalized CdS NPs are electropolymerized in the presence of thioanline‐modified Au NPs to yield an oligoaniline‐crosslinked CdS/Au NPs array. The NP‐functionalized electrode generates a photocurrent with a quantum yield that corresponds to ca. 9%. The photocurrent intensities are controlled by the potential applied on the electrode, and the redox‐state of the oligoaniline bridge. In the oxidized quinoide state of the oligoaniline units, the bridges act as electron acceptors that trap the conduction‐band electrons that are transported to the electrode and lead to high quantum yield photocurrents. The reduced π‐donor oligoaniline bridges act as π‐donor sites that associate N,N′‐dimethyl‐4,4′‐bipyridinium, MV²⁺, by donor/acceptor interactions, K_a = 5270 M^?1. The associated MV²⁺ acts as an effective trap of the conduction‐band electrons, and in the presence of triethanolamine (TEOA) as an electron donor, high photocurrent values are measured (ca. 12% quantum yield). The electropolymerization of thioaniline‐functionalized Au NPs and thioaniline‐modified CdS NPs in the presence of MV²⁺ yields a MV²⁺‐imprinted NP array. The imprinted array exhibits enhanced affinities toward the association of MV²⁺ to the oligoaniline π‐donor sites, K_a = 2.29 × 10⁴ M^?1. This results in the effective trapping of the conduction‐band electrons and an enhanced quantum yield of the photocurrent, ca. 34%. The sacrificial electron donor, TEOA, was substituted with the reversible donor I₃^?. A solar cell consisting of the imprinted CdS/Au NPs array, with MV²⁺ and I₃^?, was constructed. The cell generated a photocurrent with a quantum yield of 4.7%.