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-cells01764nas a2200229   4500008004100000022001400041245010300055210006900158260000900227300001600236490000700252520100500259653001101264653001301275653001601288653001501304653002401319100002201343700001901365700001901384856013101403       2021                        eng d  a1944-824400aReduction of hydroxyl traps and improved coupling for efficient and stable quantum dot solar cells0 aReduction of hydroxyl traps and improved coupling for efficient   cOCT   a46549-465570 v133 aProgress in quantum dot (QD)-based solar cells has been underpinned by the improvements in surface passivation and advancements in device engineering. Acute control over the surface properties is crucial to restrict the formation of in-gap trap states and improve the QD coupling in achieving conducting QD films. In this report, we demonstrate a solution-phase hybrid passivation strategy, which is beneficial in removing detrimental hydroxyl traps and improving the coupling between QDs by reducing the interdot distance. Advancement in surface passivation is translated to the long carrier lifetime, higher carrier mobility, and superior protection toward degradations in QD solids. The performance of solar cell devices is increased by 26% to reach an efficiency of 10.6%, compared to the state-of-the-art lead halide passivated solar cells. The improvement in solar cell performance is supported by the reduction of trap states and an 80 nm increase in thickness of the light-absorbing QD layer.10aligand10amobility10aquantum dot10asolar cell10asurface passivation1 aMandal, Debranjan1 aDambhare, Neha1 aRath, Arup, K.  uhttps://library.ncl.res.in/content/reduction-hydroxyl-traps-and-improved-coupling-efficient-and-stable-quantum-dot-solar-cells