No abstract

large-area fabrication without compromising the power conversion efficiency (PCE) always comes with new and unexpected challenges even for well-studied and well-optimized laboratory-scale PV technologies. For instance, non-concentrated monocrystalline silicon solar cells have reached a record 26.1% PCE, [1] but the efficiencies of most recent commercial panels are typically only up to about 22% (e.g., SunPower's Maxeon 3 panels: 22.8%, LG's Neon R: 22%, Panasonic's EverVolt: 21.7%). [2] Apart from the technical challenges, cost is the main driving factor for industry when it comes to production of modules or panels by scaling up laboratory-scale research cells. Low-cost PV technologies with performance comparable to existing industrial PV technologies may help in achieving the desired cost target, and perovskite solar cell (PSC) technology is the most suitable candidate in the current scenario. [3] The last decade saw a monumental rise in PSC technology. The perovskite absorber naturally possesses most of the desired properties for highly efficient solar cells, such as long carrier diffusion length, high carrier mobility, high light absorption coefficient, and excellent defect-tolerance. [4] Both in terms of laboratory-scale research cells and large-area panels, PSCs have seen a steep rise in PCE, reaching 25.8% for research cells, [1] and 17.9% for large-area modules with size of 802 cm 2 . [2] Further, PSC processing is relatively simple and Colloidally grown nanosized semiconductors yield extremely high-quality optoelectronic materials. Many examples have pointed to near perfect photoluminescence quantum yields, allowing for technology-leading materials such as high purity color centers in display technology. Furthermore, because of high chemical yield, and improved understanding of the surfaces, these materials, particularly colloidal quantum dots (QDs) can also be ideal candidates for other optoelectronic applications. Given the urgent necessity toward carbon neutrality, electricity from solar photovoltaics will play a large role in the power generation sector. QDs are developed and shown dramatic improvements over the past 15 years as photoactive materials in photovoltaics with various innovative deposition properties which can lead to exceptionally low-cost and high-performance devices. Once the key issues related to charge transport in optically thick arrays are addressed, QD-based photovoltaic technology can become a better candidate for practical application. In this article, the authors show how the possibilities of different deposition techniques can bring QD-based solar cells to the industrial level and discuss the challenges for perovskite QD solar cells in particular, to achieve largearea fabrication for further advancing technology to solve pivotal energy and environmental issues.The ORCID identification number(s) for the author(s) of this article can be found under https://doi.org/10.1002/adma.202107888.

The development of metal halide perovskite/perovskite heterostructures is hindered by rapid interfacial halide diffusion leading to mixed alloys rather than sharp interfaces. To circumvent this outcome, we developed an ion-blocking layer consisting of single-layer graphene (SLG) deposited between the metal halide perovskite layers and demonstrated that it effectively blocks anion diffusion in a CsPbBr 3 /SLG/CsPbI 3 heterostructure. Spatially resolved elemental analysis and spectroscopic measurements demonstrate the halides do not diffuse across the interface, whereas control samples without the SLG show rapid homogenization of the halides and loss of the sharp interface. Ultraviolet photoelectron spectroscopy, DFT calculations, and transient absorbance spectroscopy indicate the SLG has little electronic impact on the individual semiconductors. In the CsPbBr 3 / SLG/CsPbI 3 , we find a type I band alignment that supports transfer of photogenerated carriers across the heterointerface. Lightemitting diodes (LEDs) show electroluminescence from both the CsPbBr 3 and CsPbI 3 layers with no evidence of ion diffusion during operation. Our approach provides opportunities to design novel all-perovskite heterostructures to facilitate the control of charge and light in optoelectronic applications.

Perovskite quantum dots (PQDs) have many properties that make them attractive for optoelectronic applications, including expanded compositional tunability and crystallographic stabilization. While they have not achieved the same photovoltaic (PV) efficiencies of top-performing perovskite thin films, they do reproducibly show high open circuit voltage (V OC) in comparison. Further understanding of the V OC attainable in PQDs as a function of surface passivation, contact layers, and PQD composition will further progress the field and may lend useful lessons for non-QD perovskite solar cells. Here, we use photoluminescence-based spectroscopic techniques to understand and identify the governing physics of the V OC in CsPbI3 PQDs. In particular, we probe the effect of the ligand exchange and contact interfaces on the V OC and free charge carrier concentration. The free charge carrier concentration is orders of magnitude higher than in typical perovskite thin films and could be tunable through ligand chemistry. Tuning the PQD A-site cation composition via replacement of Cs+ with FA+ maintains the background carrier concentration but reduces the trap density by up to a factor of 40, reducing the V OC deficit. These results dictate how to improve PQD optoelectronic properties and PV device performance and explain the reduced interfacial recombination observed by coupling PQDs with thin-film perovskites for a hybrid absorber layer.

Cadmium bis(phenyldithiocarbamate) [Cd(PTC)] is prepared and structurally characterized. The compound crystallizes in the monoclinic space group P2/n. A one-dimensional polymeric structure is adopted in the solid state, having bridging PTC ligands and 6-coordinate pseudo-octahedral Cd atoms. The compound is soluble in DMSO, THF, and DMF and insoluble in EtOH, MeOH, CHCl, CHCl, and toluene. {CdSe[n-octylamine]} quantum belts and Cd(PTC) react to deposit epitaxial CdS shells on the nanocrystals. With an excess of Cd(PTC), the resulting thick shells contain spiny CdS nodules grown in the Stranski-Krastanov mode. Stoichiometric control affords smooth, monolayer CdS shells. A base-catalyzed reaction pathway is elucidated for the conversion of Cd(PTC) to CdS, which includes phenylisothiocyanate and aniline as intermediates, and 1,3-diphenylthiourea as a final product.