Gerrit Boschloo - Academia.edu (original) (raw)

Papers by Gerrit Boschloo

ChemPhysChem, 2019

The effect of substitutional Li doping into NiOx hole transporting layer (HTL) for use in inverte... more The effect of substitutional Li doping into NiOx hole transporting layer (HTL) for use in inverted perovskite solar cells was systematically studied. Li doped NiOx thin films with preferential crystal growth along the (111) plane were deposited using a simple solution‐based process. Mott‐Schottky analysis showed that hole carrier concentration (NA) is doubled by Li doping. Utilizing 4 % Li in NiOx improved the power conversion efficiency (PCE) of solar devices from 9.0 % to 12.6 %. Photoluminescence quenching investigations demonstrate better hole capturing properties of Li:NiOx compared to that of NiOx, leading to higher current densities by Li doping. The electrical conductivity of NiOx is improved by Li doping. Further improvements of the device were made by using an additional ZnO layer onto PCBM, to remove shunt paths, leading to a PCE of 14.2 % and a fill factor of 0.72.

Physical Chemistry Chemical Physics, 2017

The solar cell dye E6 with built-in hole acceptors efficiently separates charges after photoexcit... more The solar cell dye E6 with built-in hole acceptors efficiently separates charges after photoexcitation.

Electrochimica Acta, 2016

Analytical Chemistry, Mar 20, 2015

Solid-state dye-sensitized solar cells (sDSCs) are devoid of such issues as electrolyte evaporati... more Solid-state dye-sensitized solar cells (sDSCs) are devoid of such issues as electrolyte evaporation or leakage and electrode corrosion that are typical for traditional liquid electrolyte based DSCs. Poly(3,4-ethylenedioxythiophene) (PEDOT) is one of the most popular and efficient p-type conducting polymers that are used in sDSCs as a solid state hole-transporting material. The most convenient way to deposit this insoluble polymer into the dye-sensitized mesoporous working electrode is in-situ photoelectrochemical polymerization. Apparently, the structure and the physicochemical properties of the generated conducting polymer, which determine the photovoltaic performance of the corresponding solar cell, can be significantly affected by the preparation conditions. Therefore, a simple and fast analytical method that can reveal information on polymer chain length, possible chemical modifications, and impurities is strongly required for the rapid development of efficient solar energy-converting devices. In this contribution, we applied matrix-assisted laser desorption/ionization mass spectrometry (MALDI MS) for analysis of PEDOT directly on SDSCs. It was found that the PEDOT generated in aqueous micellar medium possesses relatively shorter polymeric chains than the PEDOT deposited from organic medium. Furthermore, the micellar electrolyte promotes a transformation of one of the thiophene terminal unit into thiophenone. The introduction of a carbonyl group into the PEDOT molecule impedes the polymer chain growth and reduces the conductivity of the final polymer film. Both the simplicity of sample preparation (only application of the organic matrix onto the solar cell is needed) and the rapidity of analysis hold the promise of making MALDI MS an essential tool for physicochemical characterization of conducting polymer-based sDSCs.

Journal of Physical Chemistry C, 2007

Accounts of Chemical Research, 2009

The journal of physical chemistry letters, Jan 5, 2015

Conductivity of methylammonium lead triiodide (MAPbI3) perovskite was measured on different mesop... more Conductivity of methylammonium lead triiodide (MAPbI3) perovskite was measured on different mesoporous metal oxide scaffolds: TiO2, Al2O3, and ZrO2, as a function of incident light irradiation and temperature. It was found that MAPbI3 exhibits intrinsic charge separation, and its conductivity stems from a majority of free charge carriers. The crystal morphology of the MAPbI3 was found to significantly affect the photoconductivity, whereas in the dark the conductivity is governed by the perovskite in the pores of the mesoporous scaffold. The temperature-dependent conductivity measurements also indicate the presence of states within the band gap of the perovskite. Despite a relatively large amount of crystal defects in the measured material, the main recombination mechanism of the photogenerated charges is bimolecular (band-to-band), which suggests that the defect states are rather inactive in the recombination. This may explain the remarkable efficiencies obtained for perovskite sola...

The Journal of Physical Chemistry, 1996

Electron trapping in electrochemical solar cells based on porous nanocrystalline TiO 2 electrodes... more Electron trapping in electrochemical solar cells based on porous nanocrystalline TiO 2 electrodes has been investigated. As light-absorbing dye, zinc 5,10,15,20-tetracarboxyphenylporphyrin is used. The spectral photocurrent response under front-and backside irradiation reveals the existence of an active region, located near the transparent conducting substrate, where charge separation takes place. Due to electron trapping, this region increases when an additional white light bias is applied. In an indifferent electrolyte, the shape of the photocurrent action spectra depends on the applied potential. The contribution of the weaker absorbing Q bands is enhanced when negative potentials are applied. In this case the electron traps in the porous TiO 2 film are filled. Their location in the bandgap is 0.5-0.6 eV below the conduction band edge. Consequently, electron trap filling enlarges the active region where charge separation takes place, which leads to an enhanced collection efficiency.

The Journal of Physical Chemistry C, 2014

ABSTRACT Nickel oxide has been used as the mesoporous electrode material for p-type dye sensitize... more ABSTRACT Nickel oxide has been used as the mesoporous electrode material for p-type dye sensitized solar cell (DSSC) for many years, but no high efficiency cells have been obtained yet. The poor results are commonly attributed to the lack of conductivity of the NiO film. In this paper we studied the electrical conduction of NiO mesoporous film with cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). We used unsensitized NiO on FTO as an electrode with no dye adsorbed on the surface. Tests made with a DSSC device-like cell (FTO-Pt-I-/I-3(-)-NiO-FTO) showed a surprisingly high Faradaic current (20 mA/cm(-2) at 1 V), proving a good electrical conductivity of mesoporous NiO. We also used lithium as dopant to improve the electrical properties of the film. The Li-doping resulted in widening the inert (not conductive) window in the CV plot. The EIS analysis clarified that this behavior is due to a strong dependence of the valence band shape and position with respect to the Li-doping concentration. Our results show that DSSC performance does not need to be limited by the conductivity of mesoporous NiO, which encourages more effort in p-type DSSC research based on this material.

The Journal of Physical Chemistry C, 2013

Linker unit modification of donor-linker-acceptor-based organic dyes was investigated with respec... more Linker unit modification of donor-linker-acceptor-based organic dyes was investigated with respect to the spectral and physicochemical properties of the dyes. The spectral response for a series of triphenylamine (TPA)-based organic dyes, called LEG1-4, was shifted into the red wavelength region and the extinction coefficient of the dyes was increased by introducing different substituted dithiophene units on the π-conjugated linker. The photovoltaic performance of dye-sensitized solar cells (DSCs) incorporating the different dyes in combination with cobaltbased electrolytes was found to be dependent on dye binding. The binding morphology of the dyes on the TiO 2 was studied using photoelectron spectroscopy, which demonstrated that the introduction of alkyl chains and different substituents on the dithiophene linker unit resulted in a larger tilt angle of the dyes with respect to the normal of the TiO 2-surface, and thereby a lower surface coverage. The good photovoltaic performance for cobalt electrolyte-based DSCs found here and by other groups using TPA-based organic dyes with a cyclopentadithiophene linker unit substituted with alkyl chains was mainly attributed to the extended spectral response of the dye, whereas the larger tilt angle of the dye with respect to the TiO 2-surface resulted in less efficient packing of the dye molecules and enhanced recombination between electrons in TiO 2 and Co(III) species in the electrolyte.

The Journal of Physical Chemistry C, 2011

We recently reported on a perylene sensitizer, ID176, which performs much better in solid state d... more We recently reported on a perylene sensitizer, ID176, which performs much better in solid state dye-sensitized solar cells than in those using liquid electrolytes with iodide/tri-iodide as the redox couple (J. Phys. Chem. C 2009, 113, 14595-14597). Here, we present a characterization of the sensitizer and of the TiO 2 /dye interface by UV-visible absorption and fluorescence spectroscopy, spectroelectrochemistry, photoelectron spectroscopy, electroabsorption spectroscopy, photoinduced absorption spectroscopy, and femtosecond transient absorption measurements. We report that the absorption spectrum of the sensitizer is red-shifted by addition of lithium ions to the surface due to a downward shift of the excited state level of the sensitizer, which is of the same order of magnitude as the downward shift of the titanium dioxide conduction band edge. Results from photoelectron spectroscopy and electrochemistry suggest that the excited state is largely located below the conduction band edge of TiO 2 but that there are states in the band gap of TiO 2 which might be available for photoinduced electron injection. The sensitizer was able to efficiently inject into TiO 2 , when a lithium salt was present on the surface, while injection was much less effective in the absence of lithium ions or in the presence of solvent. In the presence of the hole conductor 2,2 0 ,7,7 0tetrakis-(N,N-dip -methoxyphenyl-amine)-9,9 0-spirobifluorene (spiro-MeOTAD) and LiTFSI, charge separation was monitored by the emergence of a Stark shift of the dye in transient absorption spectra, and both injection and regeneration appear to be completed within 1 ps. Regeneration by spiro-MeOTAD is therefore several orders of magnitude faster than regeneration by iodide, and ID176 can even be photoreduced by spiro-MeOTAD.

The Journal of Physical Chemistry B, 2002

The anchoring of the ruthenium dye {(C 4 H 9) 4 N}[Ru(Htcterpy)(NCS) 3 ] (with tcterpy) 4,4′,4′′-... more The anchoring of the ruthenium dye {(C 4 H 9) 4 N}[Ru(Htcterpy)(NCS) 3 ] (with tcterpy) 4,4′,4′′-tricarboxy-2,2′:6′,2′′-terpyridine), the so-called black dye, onto nanocrystalline TiO 2 films has been characterized by UV-vis and FT-IR spectroscopies. FT-IR spectroscopy data suggest that dye molecules are bound to the surface by a bidentate binuclear coordination mode. The interfacial electron-transfer (ET) dynamics has been investigated by femtosecond pump-probe transient absorption spectroscopy and nanosecond laser flash photolysis. The electron-injection process from the dye excited state into the TiO 2 conduction band is biexponential with a fast component (200 (50 fs) and a slow component (20 ps). These two components can be attributed to the electron injection from the initially formed and the relaxed dye excited states, respectively. Nanosecond kinetic data suggest the existence of two distinguishable regimes (I and II) for the rates of reactions between injected electrons and oxidized dye molecules or oxidized redox species (D + or I 2 •-). The frontier between these two regimes is defined by the number of injected electrons per particle (N e), which was determined to be about 1. The present kinetic study was undertaken within regime I (N e > 1). Under these conditions, the back-electron-transfer kinetics is comparable to that in systems with other ruthenium complexes adsorbed onto TiO 2. The reduction of oxidized dye molecules by iodide results in the formation of I 2 •on a very fast time scale (<20 ns). Within regime I, the decay of I 2 •occurs in ∼100 ns via reaction with injected electrons (I 2 •-+ ef 2I-). In regime II (N e e 1), which corresponds to the normal operating conditions of dye-sensitized solar cells, the decay of I 2 •is very slow and likely occurs via the dismutation reaction (2I 2 •f I-+ I 3-). Our results predict that, under high light intensity (N e > 1), the quantum efficiency losses in dye-sensitized solar cells will be important because of the dramatic acceleration of the reaction between I 2 •and injected electrons. Mechanisms for the ET reactions involving injected electrons are proposed. The relevance of the present kinetic studies for dye-sensitized nanocrystalline solar cells is discussed.

Journal of Electroanalytical Chemistry, 1997

Electrochimica Acta, 2013

ABSTRACT

Applied Physics Letters, 2004

Transient and spectral photovoltage (PV) have been investigated for charge injection from a dye [... more Transient and spectral photovoltage (PV) have been investigated for charge injection from a dye [Ru(dcbpyH2)2(NCS)2] into transparent hole (CuSCN, CuI, CuAlO2) and electron (TiO2, SnO2:F) conductors. The PV signal rises to a maximum within 10ns to 10μs, depending on the transparent hole or electron conductor and on the mechanism of charge separation. The efficiency of hole and electron injection is of the same order while the effective lifetimes of injected charge vary between several μs and 1ms for the samples used. The thresholds for charge injection from the dye range between 1.6 and 1.8eV depending on the material on which the dye is adsorbed.

Electrochimica Acta, 2015

ABSTRACT Strong Stark effects are visible in the spectra of the organic donor-pi-acceptor dye D35... more ABSTRACT Strong Stark effects are visible in the spectra of the organic donor-pi-acceptor dye D35 when it is adsorbed onto mesoporous TiO2, both under steady state conditions and under modulated light conditions. The addition of lithium cations to the electrolyte results in a significant red shift of the D35 absorption spectrum, which is attributed to adsorption of Li+ at the TiO2 surface, resulting in a change of the electric field across the adsorbed dye molecules. The dye molecules must therefore be located inside the Helmholtz double layer at the TiO2/electrolyte interface. In photoinduced absorption (PIA) spectroscopy, modulated light is used to excite dye molecules. A significant Stark bleach is found in PIA spectra, which corresponds to a blue shift of the dye absorption spectrum upon addition of electrons to TiO2, due to an electric field across the dye monolayer. The observed bleach is reduced when the concentration of supporting electrolyte is increased, indicating local charge compensation of the electrons in TiO2 by adsorbed cations. Transient absorption studies reveal that screening of the interfacial electric field is faster at lower dye coverage compared to full monolayer coverage. Analysis of the Stark effect in dye-sensitized solar cell gives valuable information on the mechanism of charge compensation of electrons in mesoporous electrodes.

Small, 2017

Materials with controllable multifunctional abilities for optical imaging (OI) and magnetic reson... more Materials with controllable multifunctional abilities for optical imaging (OI) and magnetic resonant imaging (MRI) that also can be used in photodynamic therapy are very interesting for future applications. Mesoporous TiO 2 sub-micrometer particles are doped with gadolinium to improve photoluminescence functionality and spin relaxation for MRI, with the added benefit of enhanced generation of reactive oxygen species (ROS). The Gd-doped TiO 2 exhibits red emission at 637 nm that is beneficial for OI and significantly improves MRI relaxation times, with a beneficial decrease in spin-lattice and spin-spin relaxation times. Density functional theory calculations show that Gd 3+ ions introduce impurity energy levels inside the bandgap of anatase TiO 2 , and also create dipoles that are beneficial for charge separation and decreased electron-hole recombination in the doped lattice. The Gd-doped TiO 2 nanobeads (NBs) show enhanced ability for ROS monitored via • OH radical photogeneration, in comparison with undoped TiO 2 nanobeads and TiO 2 P25, for Gd-doping up to 10%. Cellular internalization and biocompatibility of TiO 2 @xGd NBs are tested in vitro on MG-63 human osteosarcoma cells, showing full biocompatibility. After photoactivation of the particles, anticancer trace by means of ROS photogeneration is observed just after 3 min irradiation.

Energy & Environmental Science, 2017

Further understanding and optimization of dye solar cells towards stable and efficient devices ne... more Further understanding and optimization of dye solar cells towards stable and efficient devices necessitate implementation of the characterization techniques.