We fabricated a perovskite solar cell that uses a double layer of mesoporous TiO2 and ZrO2 as a scaffold infiltrated with perovskite and does not require a hole-conducting layer. The perovskite was produced by drop-casting a solution of PbI2, methylammonium (MA) iodide, and 5-ammoniumvaleric acid (5-AVA) iodide through a porous carbon film. The 5-AVA templating created mixed-cation perovskite (5-AVA)x(MA)1- xPbI3 crystals with lower defect concentration and better pore filling as well as more complete contact with the TiO2 scaffold, resulting in a longer exciton lifetime and a higher quantum yield for photoinduced charge separation as compared to MAPbI3. The cell achieved a certified power conversion efficiency of 12.8% and was stable for >1000 hours in ambient air under full sunlight.

https://science.sciencemag.org/content/sci/345/6194/295.full.pdf

A hole-conductor-free, fully printable mesoscopic perovskite solar cell with high stability

Recently, perovskite CH3NH3PbI3 sensitizer has attracted great attention due to its superb light-harvesting characteristics. Organometallic or organic materials were mostly used as sensitizers for solid-state dye-sensitized solar cells at early stages. Inorganic nanocrystals have lately received attention as light harvesters due to their high light-absorbing properties. Metal chalcogenides have been investigated with solid-state dye-sensitized solar cells; however, the best power conversion efficiency was reported to be around 6%. CH3NH3PbX3 (X = Cl, Br, or I) perovskite sensitizer made a breakthrough in solid-state mescoscopic solar cells, where the first record efficiency of around 10% was reported in 2012 using submicrometer-thick TiO2 film sensitized with CH3NH3PbI3. A rapid increase in efficiency approaching 14% followed shortly. In this Perspective, recent progress in perovskite-sensitized solid-state mesoscopic solar cells is reviewed. On the basis of the recent achievements, a power conversion eff...

/pdf/organometal-perovskite-light-absorbers-toward-a-20-tv5d5oar52.pdf

Organometal Perovskite Light Absorbers Toward a 20% Efficiency Low-Cost Solid-State Mesoscopic Solar Cell

Dye-sensitized solar cells (DSCs) are attractive because they are made from cheap materials that do not need to be highly purified and can be printed at low cost 1 . DSCs are unique compared with almost all other kinds of solar cells in that electron transport, light absorption and hole transport are each handled by different materials in the cell 2,3 . The sensitizing dye in a DSC is anchored to a wide-bandgap semiconductor such as TiO2, SnO2 or ZnO. When the dye absorbs light, the photoexcited electron rapidly transfers to the conduction band of the semiconductor, which carries the electron to one of the electrodes 4 . A redox couple, usually comprised of iodide/triiodide (I – /I3 – ), then reduces the oxidized dye back to its neutral state and transports the positive charge to the platinized counter-electrode 5 . In 1991, O’Regan and Gratzel demonstrated that a film of titania (TiO2) nanoparticles deposited on a DSC would act as a mesoporous n-type photoanode and thereby increase the available surface area for dye attachment by a factor of more than a thousand 1 . This approach dramatically improved light absorption and brought power-conversion efficiencies into a range that allowed the DSC to be viewed as a serious competitor to other solar cell technologies 6 . A schematic and energy level diagram showing the operation of a typical DSC is shown in Fig. 1. During the 1990s and the early 2000s, researchers found that organometallic complexes based on ruthenium provided the highest power-conversion efficiencies 7,8

/pdf/the-renaissance-of-dye-sensitized-solar-cells-3i1cludwp0.pdf

The renaissance of dye-sensitized solar cells

Plasmonic metal nanostructures have been incorporated into semiconductors to enhance the solar-light harvesting and the energy-conversion efficiency. So far the mechanism of energy transfer from the plasmonic metal to semiconductors remains unclear. Herein the underlying plasmonic energy-transfer mechanism is unambiguously determined in Au@SiO2@Cu2O sandwich nanostructures by transient-absorption and photocatalysis action spectrum measurement. The gold core converts the energy of incident photons into localized surface plasmon resonance oscillations and transfers the plasmonic energy to the Cu2O semiconductor shell via resonant energy transfer (RET). RET generates electron–hole pairs in the semiconductor by the dipole–dipole interaction between the plasmonic metal (donor) and semiconductor (acceptor), which greatly enhances the visible-light photocatalytic activity as compared to the semiconductor alone. RET from a plasmonic metal to a semiconductor is a viable and efficient mechanism that can be used to ...

Photocatalytic Activity Enhanced by Plasmonic Resonant Energy Transfer from Metal to Semiconductor

Advances in solar photovoltaics are urgently needed to increase the performance and reduce the cost of harvesting solar power. Solution-processed photovoltaics are cost-effective to manufacture and offer the potential for physical flexibility. Rapid progress in their development has increased their solar-power conversion efficiencies. The nanometre (electron) and micrometre (photon) scale interfaces between the crystalline domains that make up solution-processed solar cells are crucial for efficient charge transport. These interfaces include large surface area junctions between photoelectron donors and acceptors, the intralayer grain boundaries within the absorber, and the interfaces between photoactive layers and the top and bottom contacts. Controlling the collection and minimizing the trapping of charge carriers at these boundaries is crucial to efficiency.

/pdf/materials-interface-engineering-for-solution-processed-419rhgh1js.pdf

Materials interface engineering for solution-processed photovoltaics

We present an investigation into incorporating core−shell Au−SiO2 nanoparticles into dye-sensitized solar cells. We demonstrate plasmon-enhanced light absorption, photocurrent, and efficiency for both iodide/triiodide electrolyte based and solid-state dye-sensitized solar cells. Our spectroscopic investigation indicates that plasmon-enhanced photocarrier generation competes well with plasmons oscillation damping with in the first tens of femtoseconds following light absorption.

Plasmonic dye-sensitized solar cells using core-shell metal-insulator nanoparticles.

We use ultrafast transient absorption spectroscopy with sub-20 fs time resolution and broad spectral coverage to directly probe the process of exciton fission in polycrystalline thin films of pentacene. We observe that the overwhelming majority of initially photogenerated singlet excitons evolve into triplet excitons on an ∼80 fs time scale independent of the excitation wavelength. This implies that exciton fission occurs at a rate comparable to phonon-mediated exciton localization processes and may proceed directly from the initial, delocalized, state. The singlet population is identified due to the brief presence of stimulated emission, which is emitted at wavelengths which vary with the photon energy of the excitation pulse, a violation of Kasha’s Rule that confirms that the lowest-lying singlet state is extremely short-lived. This direct demonstration that triplet generation is both rapid and efficient establishes multiple exciton generation by exciton fission as an attractive route to increased effic...

Ultrafast Dynamics of Exciton Fission in Polycrystalline Pentacene

Femtosecond and nanosecond nonlinear optical properties of alkyl phthalocyanines studied using Z-scan technique

Second harmonic generation and crystal growth of new chalcone derivatives

Received 8 May 2006; accepted 6 July 2006; published online 9 October 2006A systematic study of nonlinear absorption and scattering properties of 4.5 nm sized CdSnanocrystals dispersed in dimethylformamide with varying concentrations is reported in this paper.The study is undertaken by performing open aperture

R. Sai Santosh Kumar

Papers

Plasmonic dye-sensitized solar cells using core-shell metal-insulator nanoparticles.

Ultrafast Dynamics of Exciton Fission in Polycrystalline Pentacene

Femtosecond and nanosecond nonlinear optical properties of alkyl phthalocyanines studied using Z-scan technique

Second harmonic generation and crystal growth of new chalcone derivatives

Nonlinear absorption and scattering properties of cadmium sulphide nanocrystals with its application as a potential optical limiter