The high open‐circuit voltage (Voc) loss arising from insufficient surface passivation is the main factor that limits the efficiency of current lead sulfide colloidal quantum dots (PbS CQDs) solar ...cell. Here, synergistic passivation is performed in the direct synthesis of conductive PbS CQD inks by introducing multifunctional ligands to well coordinate the complicated CQDs surface with the thermodynamically optimal configuration. The improved passivation effect is intactly delivered to the final photovoltaic device, leading to an order lower surface trap density and beneficial doping behavior compared to the control sample. The obtained CQD inks show the highest photoluminescence quantum yield (PLQY) of 24% for all photovoltaic PbS CQD inks, which is more than twice the reported average PLQY value of ≈10%. As a result, a high Voc of 0.71 V and power conversion efficiency (PCE) of 13.3% is achieved, which results in the lowest Voc loss (0.35 eV) for the reported PbS CQD solar cells with PCE >10%, comparable to that of perovskite solar cells. This work provides valuable insights into the future CQDs passivation strategies and also demonstrates the great potential for the direct‐synthesis protocol of PbS CQDs.
Synergistic passivation is performed in the direct synthesis of conductive lead sulfide colloidal quantum dot (PbS CQD) inks. The improved passivation effect is intactly delivered to the final photovoltaic device, leading a high open‐circuit voltage (Voc)) of 0.71 V and efficiency of 13.3%, which results in the lowest Voc loss (0.35 eV) for the reported PbS CQD solar cells.
Current efforts on lead sulfide quantum dot (PbS QD) solar cells are mostly paid to the device architecture engineering and postsynthetic surface modification, while very rare work regarding the ...optimization of PbS synthesis is reported. Here, PbS QDs are successfully synthesized using PbO and PbAc2 · 3H2O as the lead sources. QD solar cells based on PbAc‐PbS have demonstrated a high power conversion efficiency (PCE) of 10.82% (and independently certificated values of 10.62%), which is significantly higher than the PCE of 9.39% for PbO‐PbS QD based ones. For the first time, systematic investigations are carried out on the effect of lead precursor engineering on the device performance. It is revealed that acetate can act as an efficient capping ligands together with oleic acid, providing better surface coverage and replace some of the harmful hydroxyl (OH) ligands during the synthesis. Then the acetate on the surface can be exchanged by iodide and lead to desired passivation. This work demonstrates that the precursor engineering has great potential in performance improvement. It is also pointed out that the initial synthesis is an often neglected but critical stage and has abundant room for optimization to further improve the quality of the resultant QDs, leading to breakthrough efficiency.
Light is shed on the effects of lead precursors on the performance of lead sulfide quantum dot (PbS QD) solar cells. The efficiency of PbS QDs synthesized from PbAc is significantly higher than that from PbO and the mechanism underneath is investigated. A new avenue is opened to improve the performance of PbS QD photovoltaic devices by lead precursor engineering.
Solution‐processed hybrid solar cells employing a low band‐gap polymer and PbSxSe1‐x alloy nanocrystals, achieving a record high PCE of 5.50% and an optimal FF of 67% are presented. The remarkable ...device efficiency can be attributed to the high‐performance active materials, the optimal polymer/NCs ratio and, more importantly, the vertical donor/(donor:acceptor)/acceptor structure which benefits charge dissociation and transport.
Lead sulphide (PbS) nanocrystals (NCs) are promising materials for low-cost, high-performance optoelectronic devices. So far, PbS NCs have to be first synthesized with long-alkyl chain organic ...surface ligands and then be ligand-exchanged with shorter ligands (two-steps) to enable charge transport. However, the initial synthesis of insulated PbS NCs show no necessity and the ligand-exchange process is tedious and extravagant. Herein, we have developed a direct one-step, scalable synthetic method for iodide capped PbS (PbS-I) NC inks. The estimated cost for PbS-I NC inks is decreased to less than 6 $·g
, compared with 16 $·g
for conventional methods. Furthermore, based on these PbS-I NCs, photodetector devices show a high detectivity of 1.4 × 10
Jones and solar cells show an air-stable power conversion efficiency (PCE) up to 10%. This scalable and low-cost direct preparation of high-quality PbS-I NC inks may pave a path for the future commercialization of NC based optoelectronics.
Almost all surfaces sensitive to the ambient environment are covered by water, whereas the impacts of water on surface-dominated colloidal quantum dot (CQD) semiconductor electronics have rarely been ...explored. Here, strongly hydrogen-bonded water on hydroxylated lead sulfide (PbS) CQD is identified. The water could pilot the thermally induced evolution of surface chemical environment, which significantly influences the nanostructures, carrier dynamics, and trap behaviors in CQD solar cells. The aggravation of surface hydroxylation and water adsorption triggers epitaxial CQD fusion during device fabrication under humid ambient, giving rise to the inter-band traps and deficiency in solar cells. To address this problem, meniscus-guided-coating technique is introduced to achieve dense-packed CQD solids and extrude ambient water, improving device performance and thermal stability. Our works not only elucidate the water involved PbS CQD surface chemistry, but may also achieve a comprehensive understanding of the impact of ambient water on CQD based electronics.
The zinc oxide (ZnO) nanoparticles (NPs) are well‐documented as an excellent electron transport layer (ETL) in optoelectronic devices. However, the intrinsic surface flaw of the ZnO NPs can easily ...result in serious surface recombination of carriers. Exploring effective passivation methods of ZnO NPs is essential to maximize the device's performance. Herein, a hybrid strategy is explored for the first time to improve the quality of ZnO ETL by incorporating stable organic open‐shell donor‐acceptor type diradicaloids. The high electron‐donating feature of the diradical molecules can efficiently passivate the deep‐level trap states and improve the conductivity of ZnO NP film. The unique advantage of the radical strategy is that its passivation effectiveness is highly correlated with the electron‐donating ability of radical molecules, which can be precisely controlled by the rational design of molecular chemical structures. The well‐passivated ZnO ETL is applied in lead sulfide (PbS) colloidal quantum dot solar cells, delivering a power conversion efficiency of 13.54%. More importantly, as a proof‐of‐concept study, this work will inspire the exploration of general strategies using radical molecules to construct high‐efficiency solution‐processed optoelectronic devices.
A new passivation strategy is proposed to improve the optoelectronic properties of the zinc oxide (ZnO) electron‐transport layer by incorporating stable organic open‐shell donor‐acceptor type diradicaloids. The passivation efficiency is found related to the electronic push‐pull effect of the diradicaloids, which can be designed by tailoring the terminal donor segments.
The direct‐synthesis of conductive PbS quantum dot (QD) ink is facile, scalable, and low‐cost, boosting the future commercialization of optoelectronics based on colloidal QDs. However, manipulating ...the QD matrix structures still is a challenge, which limits the corresponding QD solar cell performance. Here, for the first time a coordination‐engineering strategy to finely adjust the matrix thickness around the QDs is presented, in which halogen salts are introduced into the reaction to convert the excessive insulating lead iodide into soluble iodoplumbate species. As a result, the obtained QD film exhibits shrunk insulating shells, leading to higher charge carrier transport and superior surface passivation compared to the control devices. A significantly improved power‐conversion efficiency from 10.52% to 12.12% can be achieved after the matrix engineering. Therefore, the work shows high significance in promoting the practical application of directly synthesized PbS QD inks in large‐area low‐cost optoelectronic devices.
A coordination‐engineering strategy to finely manipulate the matrix thickness around the quantum dots (QDs) is reported. In this method, halogen salts are introduced into the reaction to convert the excessive insulating lead iodide into soluble iodoplumbate species. A significantly improved power conversion efficiency from 10.52% to 12.12% can be achieved after the matrix engineering based on the directly synthesized, semi‐conductive PbS QD inks.
Metal-oxide nanocrystals doped with aliovalent atoms can exhibit tunable infrared localized surface plasmon resonances (LSPRs). Yet, the range of dopant types and concentrations remains limited for ...many metal-oxide hosts, largely because of the difficulty in establishing reaction kinetics that favors dopant incorporation by using the co-thermolysis method. Here we develop cation-exchange reactions to introduce p-type dopants (Cu
, Ag
, etc.) into n-type metal-oxide nanocrystals, producing programmable LSPR redshifts due to dopant compensation. We further demonstrate that enhanced n-type doping can be realized via sequential cation-exchange reactions mediated by the Cu
ions. Cation-exchange transformations add a new dimension to the design of plasmonic nanocrystals, allowing preformed nanocrystals to be used as templates to create compositionally diverse nanocrystals with well-defined LSPR characteristics. The ability to tailor the doping profile postsynthetically opens the door to a multitude of opportunities to deepen our understanding of the relationship between local structure and LSPR properties.
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