@article {48670, title = {High open-circuit voltage in lead sulfide quantum dot solar cells via solution-phase ligand exchange with low electron affinity cadmium halides}, journal = {JOURNAL OF MATERIALS CHEMISTRY A}, volume = {11}, year = {2023}, month = {AUG}, pages = {17282-17291}, type = {Article}, abstract = {

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.

}, issn = {2050-7488}, doi = {10.1039/d3ta02191b}, author = {Dambhare, Neha V. and Biswas, Arindam and Sharma, Anjali and Shinde, Dipak Dattatray and Mahajan, Chandan and Mitra, Anurag and Rath, Arup K.} } @article {48701, title = {Multi-bandgap quantum dots ensemble for near-infrared photovoltaics}, journal = {Energy Technology}, volume = {11}, year = {2023}, month = {JUN}, type = {Article}, abstract = {

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.

}, keywords = {bulk-heterojunctions, multi-bandgap, near-infrared, quantum dots, solar cells, surface passivation}, issn = {2194-4288}, doi = {10.1002/ente.202201375}, author = {Mahajan, Chandan and Dambhare, Neha V. and Biswas, Arindam and Sharma, Anjali and Shinde, Dipak Dattatray and Rath, Arup K.} }