02162nas a2200217 4500008004100000022001400041245015500055210006900210260000800279300001600287490000700303520136200310100002301672700002001695700001901715700002901734700002101763700001801784700001901802856012301821 2023 eng d a2050-748800aHigh open-circuit voltage in lead sulfide quantum dot solar cells via solution-phase ligand exchange with low electron affinity cadmium halides0 aHigh opencircuit voltage in lead sulfide quantum dot solar cells cAUG a17282-172910 v113 a

The deployment of colloidal quantum dots (QDs) in building high-performance solar cells and other optoelectronic applications relies on the passivation of unsaturated surface atoms through ligand engineering to attain a trap-free energy bandgap and strong QD coupling while maintaining the quantum confinement effect. Despite major advancements in surface passivation strategies, the open circuit voltage (V-oc) of lead sulfide (PbS) QD solar cells is limited by undesirable sub-bandgap states and high-bandtail states. The most advanced solution-phase ligand exchange strategy for PbS QDs depends on lead halide ligands, which improved the photocurrent and fill factor in QD solar cells significantly, but only an incremental change in V-oc is observed. Here we showcase a solution-phase hybrid ligand passivation strategy for PbS QDs using shallow electron affinity cadmium halide and thiol ligands. The cadmium halide ligand treatment results in the sub-monolayer substitution of surface Pb atoms by Cd atoms. The photophysical properties of QDs improve significantly to show intense band edge emission, diminished trap emission and reduced Urbach tail states. The photovoltaic devices built using cadmium halide-treated QDs show low reverse saturation current, which helps to attain a record 0.7 V V-oc (for a 1.28 eV bandgap) and 12.3% PCE.

1 aDambhare, Neha, V.1 aBiswas, Arindam1 aSharma, Anjali1 aShinde, Dipak, Dattatray1 aMahajan, Chandan1 aMitra, Anurag1 aRath, Arup, K. uhttp://library.ncl.res.in/content/high-open-circuit-voltage-lead-sulfide-quantum-dot-solar-cells-solution-phase-ligand02122nas a2200265 4500008004100000022001400041245007200055210006900127260000800196490000700204520129400211653002501505653001801530653001801548653001701566653001601583653002401599100002101623700002301644700002001667700001901687700002901706700001901735856010201754 2023 eng d a2194-428800aMulti-bandgap quantum dots ensemble for near-infrared photovoltaics0 aMultibandgap quantum dots ensemble for nearinfrared photovoltaic cJUN0 v113 a

Narrow bandgap quantum dots (QDs) are an important class of materials for near-infrared (NIR) optoelectronic devices owing to their size-tunable bandgap and chemical root processing. In photovoltaic applications, NIR QDs could be particularly useful to complement the sub-bandgap transmission loss of NIR solar radiation from perovskite and c-Si solar cells. However, insufficient carrier extraction thickness associated with the narrow NIR excitonic bandwidth of QDs limits the conversion efficacy of the broad NIR solar spectrum. Here, we utilize a multi-bandgap QD ensemble which widens the NIR absorption bandwidth to mimic the broad solar spectrum. A solution-phase ligand passivation strategy is used to control doping properties and energy level alignment of multi-bandgap QDs. We successfully developed bulk-heterojunction solar cells using the multi-bandgap QD ensemble, which yields higher carrier extraction thickness and broader NIR absorption. The gain from NIR absorption and carrier transport resulted in higher short-circuit current generation and power conversion efficiency (PCE) in solar cell devices. The champion device shows 8.73% PCE under 1.5 AM solar illumination and 7.44% and 5.05% PCE for the NIR photons transmitted from perovskite and c-Si layers.

10abulk-heterojunctions10amulti-bandgap10anear-infrared10aquantum dots10asolar cells10asurface passivation1 aMahajan, Chandan1 aDambhare, Neha, V.1 aBiswas, Arindam1 aSharma, Anjali1 aShinde, Dipak, Dattatray1 aRath, Arup, K. uhttp://library.ncl.res.in/content/multi-bandgap-quantum-dots-ensemble-near-infrared-photovoltaics