A structure–property relationship in all‐organic dye solar cells is revealed by first‐principles molecular dynamics and real‐time time‐dependent density functional theory simulations, accompanied with experimental confirmation. An important structural feature at the interface, Ti–N anchoring, for a broad group of all‐organic dyes on TiO2 is inferred from energetics, vibrational recognition, and electronic data. This fact is contrary to the usual assumption; however, it optimizes electronic level alignment and photoelectron injection dynamics, greatly contributing to the observed efficiency improvement in all‐organic cyanoacrylate dye sensitized solar cells.

Low-voltage, low-cost, high-performance monolayer field-effect transistors are demonstrated, which comprise a densely packed, long-range ordered monolayer spin-coated from core-cladding liquid-crystalline pentathiophenes and a solution-processed high-k HfO2 -based nanoscale gate dielectric. These monolayer field-effect transistors are light-sensitive and are able to function as reporters to convert analyte binding events into electrical signals with ultrahigh sensitivity (≈10 ppb).

Organometal halide perovskite solar cells (PSCs) have emerged as one of the most promising photovoltaic technologies with efficiencies exceeding 20.3%. However, device stability problems including hysteresis in current−voltage scans must be resolved before the commercialization of PSCs. Transient absorption measurements and first-principles calculations indicate that the migration of oxygen vacancies in the TiO 2 electrode under electric field during voltage scans contributes to the anomalous hysteresis in PSCs. The accumulation of oxygen vacancies at the electrode/perovskite interface slows down charge extraction while significantly speeding up charge recombination at the interface. Moreover, nonadiabatic molecular dynamics simulations reveal that the charge recombination rates at the interface depend sensitively (with 1 order of magnitude difference) on the locations of oxygen vacancies. By intentionally reducing oxygen vacancies in the TiO 2 electrode, we substantially suppress unfavorable hysteresis in the PSC devices. This work establishes a firm link between microscopic interfacial structure and macroscopic device performance of PSCs, providing important clues for future device design and optimization.

Adsorption geometry of dye molecules on nanocrystalline TiO2 plays a central role in dye-sensitized solar cells, enabling effective sunlight absorption, fast electron injection, optimized interface band offsets, and stable photovoltaic performance. However, precise determination of dye binding geometry and proportion has been challenging due to complexity and sensitivity at interfaces. Here employing combined vibrational spectrometry and density functional calculations, we identify typical adsorption configurations of widely adopted cyanoacrylic donor-π bridge-acceptor dyes on nanocrystalline TiO2. Binding mode switching from bidentate bridging to hydrogen-bonded monodentate configuration with Ti-N bonding has been observed when dye-sensitizing solution becomes more basic. Raman and infrared spectroscopy measurements confirm this configuration switch and determine quantitatively the proportion of competing binding geometries, with vibration peaks assigned using density functional theory calculations. We further found that the proportion of dye-binding configurations can be manipulated by adjusting pH value of dye-sensitizing solutions. Controlling molecular adsorption density and configurations led to enhanced energy conversion efficiency from 2.4% to 6.1% for the fabricated dye-sensitized solar cells, providing a simple method to improve photovoltaic performance by suppressing unfavorable binding configurations in solar cell applications.

Adsorption structure of Eosin Y dyes on nanocrystalline TiO2 can be manipulated by adding a small fraction of water into organic electrolyte. Binding mode switching from hydrogen bonded monodentate to bidentate bridging configuration has been observed and confirmed by Raman and infrared spectroscopy measurements, with vibration peaks assigned using density functional theory calculations. Photovoltaic measurements on the fabricated dye-sensitized solar cells indicate that energy conversion efficiency is enhanced by manipulating molecular adsorption configuration of Eosin Y dyes. This opens a new avenue to improving photovoltaic performance by suppressing unfavorable adsorption configurations in dye solar cell devices.

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A heterostructure photovoltaic diode featuring an all-solid-state TiO2/graphene/dye ternary interface with high-efficiency photogenerated charge separation/transport is described here. Light absorption is accomplished by dye molecules deposited on the outside surface of graphene as photoreceptors to produce photoexcited electron-hole pairs. Unlike conventional photovoltaic conversion, in this heterostructure both photoexcited electrons and holes tunnel along the same direction into graphene, but only electrons display efficient ballistic transport toward the TiO2 transport layer, thus leading to effective photon-to-electricity conversion. On the basis of this ipsilateral selective electron tunnelling (ISET) mechanism, a model monolayer photovoltaic device (PVD) possessing a TiO2/graphene/acridine orange ternary interface showed ∼86.8% interfacial separation/collection efficiency, which guaranteed an ultrahigh absorbed photon-to-current efficiency (APCE, ∼80%). Such an ISET-based PVD may become a fundamental device architecture for photovoltaic solar cells, photoelectric detectors, and other novel optoelectronic applications with obvious advantages, such as high efficiency, easy fabrication, scalability, and universal availability of cost-effective materials.

Interface engineering in perovskite solar cells (PSCs) plays a key role in achieving high-power conversion efficiency (PCE, η) by suppressing electron−hole recombination and facilitating carrier injection.Here we adopt a hydrophobic molecule, 1-donecyl mercaptan (NDM), to modify the interface between MAPbI 3 and a hole transport layer (HTL). As a result, an improved PCE of PSCs from 12.75% (pristine MAPbI 3 ) to 15.04% (modified MAPbI 3 with NDM) is achieved, along with long-term antimoisture characteristics. First-principles simulations unravel an enhanced driving force for hole injection from MAPbI 3 to the HTL upon NDM adsorption, providing atomic-scale insights into the improved PCE. The combined experiment and simulation efforts offer a simple but effective molecular approach to fabricate PSCs with a higher PCE and better moisture tolerance.