Dye-sensitized solar cells (DSSCs) are based on molecular and nanometer-scale components. Record cell efficiencies of 12%, promising stability data, and means of energy efficient production methods have been accomplished. As selling points for the DSSC tec ...

Wiley2018

Interfacial Engineering of Metal Oxides for Highly Stable Halide Perovskite Solar Cells

Nikolaos Vlachopoulos, Ulf Anders Hagfeldt, Wolfgang Richard Tress, Kazuteru Nonomura, Hui-Seon Kim, Zaiwei Wang, Monica Marcela Lira Cantu, Anna Morales Melgares, Haibing Xie

Oxides employed in halide perovskite solar cells (PSCs) have already demonstrated to deliver enhanced stability, low cost, and the ease of fabrication required for the commercialization of the technology. The most stable PSCs configuration, the carbon-base ...

WILEY2018

Impact of Local Electric Fields on Charge-Transfer Processes at the TiO2/Dye/Electrolyte Interface

Nikolaos Vlachopoulos

Photoinduced electron -transfer processes at the TiO2/ dye/electrolyte interface are vital for various emerging technologies. Here, the impact of the local electric field at this interface on the charge -transfer processes was investigated in two aspects: ...

Amer Chemical Soc2017

Perovskite solar cell - electrochemical double layer capacitor interplay

Michael Graetzel, Nikolaos Vlachopoulos, Ulf Anders Hagfeldt, Juan-Pablo Correa-Baena, Michael Saliba, Silver Hamill Turren Cruz

We demonstrate that by a proper design of a system comprising a perovskite solar cell (PSC) coupled to an electrochemical double-layer capacitor (EDLC), it is possible to simultaneously improve both the PSC and EDLC performance and outperform each single u ...

Elsevier2017

Additives, Hole Transporting Materials and Spectroscopic Methods to Characterize the Properties of Perovskite Films

Michael Graetzel, Shaik Mohammed Zakeeruddin, Nikolaos Vlachopoulos, Ulf Anders Hagfeldt, Marko Stojanovic, Amita Ummadisingu, Jiyoun Seo, Michael Saliba

The achievement of high efficiency and high stability in perovskite solar cells (PSCs) requires optimal selection and evaluation of the various components. After a brief introduction to the perovskite materials and their historical evolution, the first par ...

Schweizerische Chemische Gesellschaft2017

Incorporation of Counter Ions in Organic Molecules: New Strategy in Developing Dopant-Free Hole Transport Materials for Efficient Mixed-Ion Perovskite Solar Cells

Nikolaos Vlachopoulos, Ulf Anders Hagfeldt, Liang Wang, Lin Yang, Monica Marcela Lira Cantu, Jiahuan Zhang

Hole transport matertial (HTM) as charge selective layer in perovskite solar cells (PSCs) plays an important role in achieving high power conversion efficiency (PCE). It is known that the dopants and additives are necessary in the HTM in order to improve t ...

Wiley-V C H Verlag Gmbh2017

Efficient Blue-Colored Solid-State Dye-Sensitized Solar Cells: Enhanced Charge Collection by Using an in Situ Photoelectrochemically Generated Conducting Polymer Hole Conductor

Michael Graetzel, Nikolaos Vlachopoulos, Ulf Anders Hagfeldt, Thomas Wesley Holcombe, Jiahuan Zhang, Yan Hao

A high power conversion efficiency (PCE) of 5.5% was achieved by efficiently incorporating a diketopyrrolopyrrole-based dye with a conducting polymer poly(3,4-ethylenediothiophene) (PEDOT) hole-transporting material (HTM) that was formed in situ, compared ...

Wiley-V C H Verlag Gmbh2016

Studies on the Interfacial Electric Field and Stark Effect at the TiO2/Dye/Electrolyte Interface

Nikolaos Vlachopoulos, Anna Eriksson, Yan Hao

Interfaces of dye-sensitized TiO2 nanoparticles with electrolytes or hole conductors have been widely applied in photoelectrochemical cells. However, the fundamental understanding of their properties and function is still poor. Herein, we demonstrate that ...

American Chemical Society2016

The Role of 3D Molecular Structural Control in New Hole Transport Materials Outperforming Spiro-OMeTAD in Perovskite Solar Cells

Nikolaos Vlachopoulos, Ulf Anders Hagfeldt, Lin Yang, Peng Liu, Jiahuan Zhang

Wiley-VCH Verlag Berlin2016

Copper Bipyridyl Redox Mediators for Dye-Sensitized Solar Cells with High Photovoltage

Jacques-Edouard Moser, Shaik Mohammed Zakeeruddin, Nikolaos Vlachopoulos, Ladislav Kavan, Ulf Anders Hagfeldt, Norman Pellet, Yiming Cao, Fabrizio Giordano, Yasemin Saygili, Marina Freitag, Magnus Söderberg

Redox mediators play a major role determining the photocurrent and the photovoltage in dye-sensitized solar cells (DSCs). To maintain the photocurrent, the reduction of oxidized dye by the redox mediator should be significantly faster than the electron bac ...

American Chemical Society2016

Efficient solid-state dye sensitized solar cells: The influence of dye molecular structures for the in-situ photoelectrochemically polymerized PEDOT as hole transporting material

Mohammad Khaja Nazeeruddin, Nikolaos Vlachopoulos, Ulf Anders Hagfeldt, Jiahuan Zhang

Solid-state dye sensitized solar cells (sDSCs) with organic small molecule hole transporting materials (HTMs) have limited efficiencies due to the incomplete pore filling of the HTMs in the thick mesoporous electrodes and the low hole conductivity of HTMs. ...

Elsevier Science Bv2016

The effect of mesoporous TiO2 pore size on the performance of solid-state dye sensitized solar cells based on photoelectrochemically polymerized Poly(3,4-ethylenedioxythiophene) hole conductor

Nikolaos Vlachopoulos, Ulf Anders Hagfeldt, Jiahuan Zhang

Photoelectrochemical polymerization of poly(3,4-ethylenedioxythiphene) (PEDOT) has recently been introduced and widely investigated for fabrication of the hole transporting material (HTM) in highly efficient solid state dye sensitized solar cells (sDSCs). ...

Pergamon-Elsevier Science Ltd2016

Constructive Effects of Alkyl Chains: A Strategy to Design Simple and Non-Spiro Hole Transporting Materials for High-Efficiency Mixed-Ion Perovskite Solar Cells

Nikolaos Vlachopoulos, Ulf Anders Hagfeldt, Juan-Pablo Correa-Baena, Peng Liu, Mahboobeh Hadadian, Jiahuan Zhang

Wiley-V C H Verlag Gmbh2016

Strategy to Boost the Efficiency of Mixed-Ion Perovskite Solar Cells: Changing Geometry of the Hole Transporting Material

Nikolaos Vlachopoulos, Ulf Anders Hagfeldt, Jiahuan Zhang

The hole transporting material (HTM) is an essential component in perovskite solar cells (PSCs) for efficient extraction and collection of the photoinduced charges. Triphenylamine- and carbazole-based derivatives have extensively been explored as alternati ...

Amer Chemical Soc2016

Efficient dye regeneration at low driving force achieved in triphenylamine dye LEG4 and TEMPO redox mediator based dye-sensitized solar cells

Nikolaos Vlachopoulos, Ulf Anders Hagfeldt, Yan Hao

Minimizing the driving force required for the regeneration of oxidized dyes using redox mediators in an electrolyte is essential to further improve the open-circuit voltage and efficiency of dye-sensitized solar cells (DSSCs). Appropriate combinations of r ...

Royal Society of Chemistry2015

Matrix-Assisted Laser Desorption/Ionization Mass Spectrometric Analysis of Poly(3,4-ethylenedioxythiophene) in Solid-State Dye-Sensitized Solar Cells: Comparison of In Situ Photoelectrochemical Polymerization in Aqueous Micellar and Organic Media

Nikolaos Vlachopoulos, Ulf Anders Hagfeldt, Lin Yang, Jiahuan Zhang

Solid-state dye-sensitized solar cells (sDSCs) are devoid of such issues as electrolyte evaporation or leakage and electrode corrosion, which are typical for traditional liquid electrolyte-based DSCs. Poly(3,4-ethylenedioxythiophene) (PEDOT) is one of the ...

American Chemical Society2015

Carbon nanotube film replacing silver in high-efficiency solid-state dye solar cells employing polymer hole conductor

Nikolaos Vlachopoulos, Ulf Anders Hagfeldt, Jiahuan Zhang

A semitransparent, flexible single-walled carbon nanotube (SWCNT) film was efficiently used in place of evaporated silver as the counter electrode of a poly(3,4-ethylenedioxythiophene) polymer-based solid-state dye solar cell (SSDSC): the solar-to-electric ...

Springer Verlag2015

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