@article {43541,
	title = {Colossal photo-conductive gain in low temperature processed TiO2 films and their application in quantum dot solar cells},
	journal = {Applied Physics Letters},
	volume = {110},
	year = {2017},
	month = {MAR},
	pages = {Article Number: 123902},
	abstract = {Colloidal quantum dot (QD) solar cells have seen remarkable progress in recent past to reach the certified efficiency of 10.6\%. Anatase titanium oxide (TiO2) is a widely studied n-type widow layer for the collection of photogenerated electrons in QD solar cells. Requirement of high temperature (similar to 500 degrees C) processing steps proved to be disadvantageous for its applications in flexible solar cells and roll to roll processing, and it also has adverse commercial implications. Here, we report that solar light exposure to low temperature processed (80 degrees C-150 degrees C) TiO2 and niobium doped TiO2 films leads to unprecedented enhancement in their electron densities and electron mobilities, which enables them to be used as efficient n-type layers in quantum dot solar cells. Such photoinduced high conducting states in these films show gradual decay over hours after the light bias is taken off and can be retrieved under solar illumination. On the contrary, TiO2 films processed at 500 degrees C show marginal photo induced enhancements in their characteristics. In bilayer configuration with PbS QDs, photovoltaic devices based on low temperature processed TiO2 films show improved performance over high temperature processed TiO2 films. The stability of photovoltaic devices also improved in low temperature processed TiO2 films under ambient working conditions. Published by AIP Publishing.},
	doi = {10.1063/1.4978766},
	author = {Mandal, Debranjan and Goswami, Prasenjit N. and Rath, Arup K.}
}
@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 = {<p>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.</p>},
	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.}
}
@article {48115,
	title = {Composition and surface morphology invariant high on-off ratio from an organic memristor},
	journal = {ACS Applied Electronic Materials},
	volume = {4},
	year = {2022},
	month = {MAR },
	pages = {1109-1116},
	type = {Article},
	abstract = {<p>Material composition plays a crucial role in the device performance; thus, nonvolatile memory devices from a small molecule named 5-mercapto-1-methyl tetrazole (MMT) in an insulating polymer matrix of poly(4-vinyl pyridine) (PVP) were fabricated. The composition of the active material in the device was varied to observe its influence on the device{\textquoteright}s electronic properties. The device with a more or less weight ratio of MMT has a much smoother surface morphology, whereas when the contributions of MMT and PVP were equal, the average surface roughness increased. However, the maximum on-off current ratio for all the devices is 10(5), suggesting that the MMT molecule does not show any change in its characteristic properties when surrounded by an insulating material. When the device was fabricated without the polymer matrix, the surface morphology of the device completely changed as it was filled with large holes. These holes provide short-circuited pathways for the current by forming the direct metal contact between the top and bottom electrodes. The carrier transport through these devices follows various conduction mechanisms. Some of the dominating conduction mechanisms are direct tunneling and trap-free and trap-assisted space-charge-limited conduction.</p>
},
	keywords = {Nonvolatile memory, Polymer, small molecule, space-charge, tunneling},
	doi = {10.1021/acsaelm.1c01234},
	author = {Betal, Atanu and Bera, Jayanta and Sharma, Ashish and Rath, Arup K. and Sahu, Satyajit}
}
