02718nas a2200265   4500008004100000022001400041245008000055210006900135260000800204300001400212490000600226520192400232653001502156653001102171653001902182653001602201653001602217653001402233100001902247700001902266700001802285700001902303700001902322856011102341       2021                        eng d  a2574-097000aCrack-free conjugated PbS quantum dot-hole transport layers for solar cells0 aCrackfree conjugated PbS quantum dothole transport layers for so  cAPR  a4016-40250 v43 a<p>Colloidal quantum dots (QDs) benefit from solution-phase processing and band-gap tuning for their application in solar cell development. Today'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>10aEfficiency10aligand10apolydispersity10aquantum dot10asolar cells10athin film1 aSharma, Ashish1 aDambhare, Neha1 aBera, Jayanta1 aSahu, Satyajit1 aRath, Arup, K.  uhttps://library.ncl.res.in/content/crack-free-conjugated-pbs-quantum-dot-hole-transport-layers-solar-cells