Organometallic trihalide perovskites are solution-processed semiconductors that have made great strides in third-generation thin film light-harvesting and light-emitting optoelectronic devices. ...Recently, it has been demonstrated that large, high-purity single crystals of these perovskites can be synthesized from the solution phase. These crystals’ large dimensions, clean bandgap, and solid-state order have provided us with a suitable medium to observe and quantify two-photon absorption in perovskites. When CH3NH3PbBr3 single crystals are pumped with intense 800 nm light, we observe band-to-band photoluminescence at 572 nm, indicative of two-photon absorption. We report the nonlinear absorption coefficient of CH3NH3PbBr3 perovskites to be 8.6 cm GW–1 at 800 nm, comparable to epitaxial single-crystal semiconductors of similar bandgap. We have leveraged this nonlinear process to electrically autocorrelate a 100 fs pulsed laser using a two-photon perovskite photodetector. This work demonstrates the viability of organometallic trihalide perovskites as a convenient and low-cost nonlinear absorber for applications in ultrafast photonics.
Bandtail states in disordered semiconductor materials result in losses in open-circuit voltage (V
) and inhibit carrier transport in photovoltaics. For colloidal quantum dot (CQD) films that promise ...low-cost, large-area, air-stable photovoltaics, bandtails are determined by CQD synthetic polydispersity and inhomogeneous aggregation during the ligand-exchange process. Here we introduce a new method for the synthesis of solution-phase ligand-exchanged CQD inks that enable a flat energy landscape and an advantageously high packing density. In the solid state, these materials exhibit a sharper bandtail and reduced energy funnelling compared with the previous best CQD thin films for photovoltaics. Consequently, we demonstrate solar cells with higher V
and more efficient charge injection into the electron acceptor, allowing the use of a closer-to-optimum bandgap to absorb more light. These enable the fabrication of CQD solar cells made via a solution-phase ligand exchange, with a certified power conversion efficiency of 11.28%. The devices are stable when stored in air, unencapsulated, for over 1,000 h.
The detection of photons underpins imaging, spectroscopy, fibre-optic communications and time-gated distance measurements. Nanostructured materials are attractive for detection applications because ...they can be integrated with conventional silicon electronics and flexible, large-area substrates, and can be processed from the solution phase using established techniques such as spin casting, spray coating and layer-by-layer deposition. In addition, their performance has improved rapidly in recent years. Here we review progress in light sensing using nanostructured materials, focusing on solution-processed materials such as colloidal quantum dots and metal nanoparticles. These devices exhibit phenomena such as absorption of ultraviolet light, plasmonic enhancement of absorption, size-based spectral tuning, multiexciton generation, and charge carrier storage in surface and interface traps.
Rapid progress in identifying biomarkers that are hallmarks of disease has increased demand for high-performance detection technologies. Implementation of electrochemical methods in clinical analysis ...may provide an effective answer to the growing need for rapid, specific, inexpensive, and fully automated means of biomarker analysis. This Review summarizes advances from the past 5 years in the development of electrochemical sensors for clinically relevant biomolecules, including small molecules, nucleic acids, and proteins. Various sensing strategies are assessed according to their potential for reaching relevant limits of sensitivity, specificity, and degrees of multiplexing. Furthermore, we address the remaining challenges and opportunities to integrate electrochemical sensing platforms into point-of-care solutions.
The detection of infrared radiation enables night vision, health monitoring, optical communications and three-dimensional object recognition. Silicon is widely used in modern electronics, but its ...electronic bandgap prevents the detection of light at wavelengths longer than about 1,100 nanometres. It is therefore of interest to extend the performance of silicon photodetectors into the infrared spectrum, beyond the bandgap of silicon. Here we demonstrate a photovoltage field-effect transistor that uses silicon for charge transport, but is also sensitive to infrared light owing to the use of a quantum dot light absorber. The photovoltage generated at the interface between the silicon and the quantum dot, combined with the high transconductance provided by the silicon device, leads to high gain (more than 10
electrons per photon at 1,500 nanometres), fast time response (less than 10 microseconds) and a widely tunable spectral response. Our photovoltage field-effect transistor has a responsivity that is five orders of magnitude higher at a wavelength of 1,500 nanometres than that of previous infrared-sensitized silicon detectors. The sensitization is achieved using a room-temperature solution process and does not rely on traditional high-temperature epitaxial growth of semiconductors (such as is used for germanium and III-V semiconductors). Our results show that colloidal quantum dots can be used as an efficient platform for silicon-based infrared detection, competitive with state-of-the-art epitaxial semiconductors.
The architecture of colloidal quantum dot (CQD) solar cells was investigated, and their use as the primary active layer of solar cells to promote rapid advances in energy conversion efficiency is ...detailed.
Perovskite photonic sources Sutherland, Brandon R; Sargent, Edward H
Nature photonics,
05/2016, Letnik:
10, Številka:
5
Journal Article
Recenzirano
Odprti dostop
The field of solution-processed semiconductors has made great strides; however, it has yet to enable electrically driven lasers. To achieve this goal, improved materials are required that combine ...efficient (>50% quantum yield) radiative recombination under high injection, large and balanced charge-carrier mobilities in excess of 10 cm2 V-1 s-1 , free-carrier densities greater than 1017 cm-3 and gain coefficients exceeding 104 cm-1 . Solid-state perovskites are -- in addition to galvanizing the field of solar electricity -- showing great promise in photonic sources, and may be the answer to realizing solution-cast laser diodes. Here, we discuss the properties of perovskites that benefit light emission, review recent progress in perovskite electroluminescent diodes and optically pumped lasers, and examine the remaining challenges in achieving continuous-wave and electrically driven lasing.
Colloidal quantum dots (CQDs) are solution‐processed semiconductors of interest in low‐cost photovoltaics. Tuning of the bandgap of CQD films via the quantum size effect enables customization of ...solar cells’ absorption profile to match the sun's broad visible‐ and infrared‐containing spectrum reaching the earth. Here we review recent progress in the realization of low‐cost, efficient solar cells based on CQDs. We focus in particular on CQD materials and approaches that provide both infrared and visible‐wavelength solar power conversion CQD photovoltaics now exceed 5% solar power conversion efficiency, achieved by the introduction of a new architecture, the depleted‐heterojunction CQD solar cell, that jointly maximizes current, voltage, and fill factor. CQD solar cells have also seen major progress in materials processing for stability, recently achieving extended operating lifetimes in an air ambient. We summarize progress both in device operation and also in gaining new insights into materials properties and processing – including new electrical contact materials and deposition techniques, as well as CQD synthesis, surface treatments, film‐forming technologies – that underpin these rapid advances.
Infrared colloidal quantum dots that absorb most of the solar radiation enable potential efficient and low‐cost photovoltaic devices. Careful optimization of quantum dot passivation and device configuration leads to solar cells with AM1.5G efficiency as high as 5.1%
Building devices from colloidal quantum dots Kagan, Cherie R.; Lifshitz, Efrat; Sargent, Edward H. ...
Science (American Association for the Advancement of Science),
08/2016, Letnik:
353, Številka:
6302
Journal Article
Recenzirano
The continued growth of mobile and interactive computing requires devices manufactured with low-cost processes, compatible with large-area and flexible form factors, and with additional ...functionality. We review recent advances in the design of electronic and optoelectronic devices that use colloidal semiconductor quantum dots (QDs). The properties of materials assembled of QDs may be tailored not only by the atomic composition but also by the size, shape, and surface functionalization of the individual QDs and by the communication among these QDs. The chemical and physical properties of QD surfaces and the interfaces in QD devices are of particular importance, and these enable the solution-based fabrication of low-cost, large-area, flexible, and functional devices. We discuss challenges that must be addressed in the move to solution-processed functional optoelectronic nanomaterials.
PDF
