@article { ISI:000246978800037, title = {DMFC at low air flow operation: study of parasitic hydrogen generation}, journal = {Electrochimica Acta}, volume = {52}, number = {19}, year = {2007}, month = {MAY}, pages = {6060-6067}, publisher = {PERGAMON-ELSEVIER SCIENCE LTD}, type = {Article}, address = {THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND}, abstract = {

In this paper, the effect of hydrogen generation in direct methanol fuel cells (DMFC) is described. Under certain operating conditions hydrogen generation occurs in DMFC causing an additional methanol consumption and a decrease of the cell voltage. For the present experiments a segmented cell with an active area of 244 cm 2 is used. The cell has 196 segments which are regularly distributed on the whole area. By this experimental setup hydrogen generation was found in regions with insufficient air supply. Hydrogen generation was analyzed by systematically applying different air flow rates and detecting the local current densities. The theory for hydrogen generation is confirmed by the results obtained from the segmented cell. A correlation between open circuit voltage (OCV), air flow rate and hydrogen generation was observed. Furthermore, half-cell measurements with different methanol concentrations were performed and used for analyzing the processes during hydrogen generation. The work clearly indicates the importance of sufficient cathode air supply for DMFC. Starved cathode areas not only do not contribute to the overall current generation but in addition reduce the power and efficiency by the parasitic generation of hydrogen. (C) 2007 Elsevier Ltd. All rights reserved.

}, keywords = {DMFC, Efficiency, electrolytic hydrogen evolution, oxygen depletion, side-effects}, issn = {0013-4686}, doi = {10.1016/j.electacta.2007.03.067}, author = {Dohle, H. and Mergel, J. and Ghosh, P. C.} } @article { ISI:000363347800036, title = {Photochemical performance of ZnO nanostructures in dye sensitized solar cells}, journal = {Solid State Sciences}, volume = {48}, year = {2015}, month = {OCT}, pages = {237-243}, publisher = {ELSEVIER SCIENCE BV}, address = {PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS}, abstract = {

In this work, the photoconversion efficiencies of ZnO having diverse microstructures and structural defects have been investigated. A conversion efficiency of 138\% was achieved for the DSSCs fabricated with as prepared ZnO nanorods having minimum vacancy defects and a favourable one dimensional directional pathway for electron conduction. The DSSCs fabricated with ZnO nanoparticles exhibited relatively low conversion efficiency of 1.004\% probably due to multiple trapping/detrapping phenomena within the grain boundaries and ZnO flowers though exhibited a high dye adsorption capability exhibited the lowest conversion efficiency of 0.59\% due to a high concentration of structural defects. Based on the experimental evidences, we believe that the type of defects and their concentrations are more important than shape in controlling the overall performance of ZnO based DSSCs. (C) 2015 Elsevier Masson SAS. All rights reserved.

}, keywords = {DSSC, Efficiency, Emission, Structural defects, ZnO}, issn = {1293-2558}, doi = {10.1016/j.solidstatesciences.2015.08.014}, author = {Das, Partha Pratim and Mukhopadhyay, Soumita and Agarkar, Shruti A. and Jana, Arpita and Devi, P. Sujatha} } @article {47385, title = {Crack-free conjugated PbS quantum dot-hole transport layers for solar cells}, journal = {ACS Applied Nano Materials}, volume = {4}, year = {2021}, month = {APR}, pages = {4016-4025}, type = {Article}, abstract = {

Colloidal quantum dots (QDs) benefit from solution-phase processing and band-gap tuning for their application in solar cell development. Today{\textquoteright}s QD solar cells rely on solid-state ligand exchange (SLE) to replace bulky oleic acid (OA) ligands with small 1,2-ethanedithiol (EDT) ligands to develop a conducting hole transport layer (HTL). High volume contraction in EDT conjugated QD films, however, leads to crack and porosity in the HTL, which is a major cause of concern for the device reproducibility and large-area solar cell development. We show that partial removal of the OA ligands in the solution phase reduces the volume contraction in solid films, thereby allowing the growth of crack-free QD films in the SLE process. The cleaning of QDs by repeated precipitation and redispersion using a protic methanol (MeOH) solvent helps with partial removal of the OA ligands, but it is detrimental to the electronic properties of QDs. We develop a one-step solution-phase partial ligand-exchange process using ammonium salts, which enable partial replacement of the OA ligands and passivation of the QD surface. Introduction of the facile partial ligand-exchange process eliminates the need for tedious and wasteful multiple cleaning steps with MeOH, while improving the photophysical properties of QDs. The advancement in QD processing helps to build crack-free, smooth, and conjugated QD films for their deployment as HTLs in solar cell development. Partial ligand exchange with NH4SCN leads to a 1.5 times increase in p doping and mobility over multiple MeOH-cleaned PbS QD films. HTLs developed using NH4SCN QDs show an improved photovoltaic performance to attain a 10.5\% power conversion efficiency. Improvement in the depletion width and hole collection efficiency leads to a superior photovoltaic performance, as confirmed from experimental studies and one-dimensional solar cell capacitance simulation.

}, keywords = {Efficiency, ligand, polydispersity, quantum dot, solar cells, thin film}, issn = {2574-0970}, doi = {10.1021/acsanm.1c00373}, author = {Sharma, Ashish and Dambhare, V. Neha and Bera, Jayanta and Sahu, Satyajit and Rath, Arup K.} }