@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.} } @article {49241, title = {Solution-phase ligand engineering for all-quantum-dot near-infrared light-emitting diodes}, journal = {ACS Applied Nano Materials}, volume = {7}, year = {2024}, month = {APR }, pages = {9126-9135}, type = {Article}, abstract = {

Strong emission over a wide near-infrared (NIR) region makes lead sulfide quantum dots (QDs) a preferred material in building NIR light-emitting diodes (NIR-LEDs) for numerous applications. Narrow-bandgap emitter QDs blended in the matrix of high-band gap QDs offer a simple yet powerful architectural platform for building high-performance NIR-LEDs. So far, the all-QD-based blend architecture has been realized using a poorly controlled solid-state ligand exchange approach. Advanced solution-phase ligand exchange, which offers greater control over surface passivation, is yet to be realized in all-QD LED device construction. We observe that the solution-phase ligand exchange from the optimized lead halide and thiol ligand combination, used in high-performing QD solar cell construction, is inefficient in realizing efficient all-QD LEDs, which could have restricted the adoption of the solution-phase ligand exchange thus far. Here, we introduce an innovative dual-ligand strategy to build all-QD-based NIR-LEDs using an advanced solution-phase ligand exchange approach. Through ligand engineering of matrix QDs, we managed to improve photoluminescence quantum yield (40\%), reduce trap density (10(14) cm(-3)), and prolong carrier lifetime (832 ns). The LED devices benefit from improved electronic properties and balanced carrier injection to yield 6\% EQE and 7.7\% PCE, which are six times higher than those of state-of-the-art ligands.

}, keywords = {electroluminescence, lead sulfide, ligand passivation, light-emitting diodes, near-infrared, quantumdots}, doi = {10.1021/acsanm.4c00634}, author = {Biswas, Arindam and Mitra, Anurag and Sharma, Ashish and Shinde, Dipak Dattatray and Dambhare, V. Neha and Sharma, Anjali and Mahajan, Chandan and Rath, Arup K.} } @article {49496, title = {Synergistic improvement of narrow bandgap PbS quantum dot solar cells through surface ligand engineering, near-infrared spectral matching, and enhanced electrode transparency}, journal = {ACS Applied Materials \& Interfaces}, volume = {17}, year = {2025}, month = {JAN}, pages = {6614-6625}, type = {Article}, abstract = {

The tunability of the energy bandgap in the near-infrared (NIR) range uniquely positions colloidal lead sulfide (PbS) quantum dots (QDs) as a versatile material to enhance the performance of existing perovskite and silicon solar cells in tandem architectures. The desired narrow bandgap (NBG) PbS QDs exhibit polar (111) and nonpolar (100) terminal facets, making effective surface passivation through ligand engineering highly challenging. Despite recent breakthroughs in surface ligand engineering, NBG PbS QDs suffer from uncontrolled agglomeration in solid films, leading to increased energy disorder and trap formation. The limited NIR transparency of commonly used indium-doped tin oxide (ITO) electrodes and inadequate NIR radiation from commercially available solar simulators further compromise the true performance of NBG PbS QDs in solar cells. Here, we employ a hybrid ligand strategy based on inorganic cadmium halide and organic thiol molecules, leading to the partial substitution of surface Pb atoms with Cd heteroatoms. This hybrid ligand strategy substantially reduces undesired QD fusion in solid films, improving the photophysical and electronic properties. By modulating the thickness of the ITO layer and managing refraction loss through a ZnO layer coating, we improved NIR transparency to above 80\%. We combine an NIR light source with a solar simulator to achieve near-ideal spectral matching for a broader range with standard AM1.5G illumination. Enhancements in surface passivation of QDs, improvements in NIR transparency of electrodes, and a spectral matched light source setup help us achieve solar cell power conversion efficiencies of 12.4\%, 4.48\%, and 1.37\% under AM 1.5G, perovskite filter, and silicon filter illuminations, respectively. A record open-circuit voltage (V oc) of 0.54 V and short-circuit current density (J sc) of 38.5 mA/cm2 are achieved under AM 1.5G illumination. We attribute these advancements in photovoltaic parameters to the reduction in Urbach tail states and intermediate trap density originating from superior surface passivation of QDs.

}, keywords = {lead sulfide, ligand passivation, near-infrared, quantum dots, solar cell, tandem solarcell}, issn = {1944-8244}, doi = {10.1021/acsami.4c22334}, author = {Sharma, Anjali and Shinde, Dipak Dattatray and Mahajan, Chandan and Dambhare, Neha V. and Biswas, Arindam and Mitra, Anurag and Girade, Vrushali S. and Rath, Arup K.} }