No abstract

Hybrid halide perovskite solar cells were first demonstrated in 2009 with cell efficiency quickly soaring from below 10% to more than 23% in a few years. Halide perovskites have the desirable processing simplicity but are very fragile when exposed to water and heat. This fragility represents a great challenge for the achievement of their full practical potential in photovoltaic technologies. To address this problem, here we review the recent development of the mixed-dimensional perovskites, whereby the trade-off between power conversion efficiency and stability of the material can be finely tuned using organic amine cations with different sizes and functionalities.

We propose that 1 + 1 + 1 triple-junction solar cells can provide an increased efficiency, as well as a higher open circuit voltage, compared to tandem solar cells.

The surface, interfaces and grain boundaries of a halide perovskite film carry critical tasks in achieving as well as maintaining high solar cell performance due to the inherently defective nature...

Near-infrared light-emitting diodes based on solution-processed semiconductors, such as organics, halide perovskites and colloidal quantum dots, have emerged as a viable technological platform for biomedical applications, night vision, surveillance and optical communications. The recently gained increased understanding of the materials structure-photophysical property relationship has enabled the design of efficient emitters leading to devices with external quantum efficiencies exceeding 20%. Despite significant strides made, challenges remain in achieving high radiance, reducing efficiency roll-off, and extending operating lifetime. This review summarizes recent advances on emissive materials synthetic methods and device key attributes that collectively contribute to improved performance of the fabricated light-emitting devices.Light-emitting diodes (LEDs) with emission in the near-infrared (NIR) part of the spectrum (700-2500 nm) (termed as NIR-LEDs) support a large variety of applications such as optical diagnosis and biomedical imaging 1 , optical communication, remote sensing, security, night vision and data storage 2 .The specific application field determines the spectral range of interest within the NIR (Fig. 1a). With regard to in vivo bioimaging, the semi-transparency of biological tissues, oxygenated and deoxygenated blood in specific NIR wavelength regions, also known as biological windows, makes NIR particularly appealing for optical imaging, biomedical sensing and photodynamic therapy. In the field of optical wireless communications, the spectral range is also divided in bands, which correlate with the wavelength regions where optical fibres have small transmission losses 3 . NIR-LEDs are also in demand 3 for security authentication, optogenetics, life-cycle management of crops, light fidelity and surveillance 4 .Common NIR-LEDs are epitaxial heterostructures of III-V inorganic semiconductors (e.g. GaAs, InGaAs, InGaAlAs) [5][6][7] . Commercially available products also employ inorganic phosphors, namely compounds doped with transition metals 8 , or rare-earth trivalent ions 9 . An external quantum efficiency (EQE) of 72% at 880 nm has been reported for an AlGaAs/GaAs/AlGaAs III-V-LED 6 , and 44.5% at 775 nm for LEDs based on LaMgGa 11 O 19 :Cr 3+ phosphors 10 . However, III-V LEDs require post fabrication substrate replacement with high reflective mirror structures to increase their poor power output originating from the refractive index mismatch between those materials (>3.0) 7 and common substrates.Additionally, inorganic phosphors require very high temperature sintering treatment (above 1000 o C).These processing requirements are an obstacle for low-cost, handheld portable implementations. Organic (OSCs) 11 , metal-halide perovskite (HPs) 12 , and colloidal quantum dot (QD) 13 semiconductors, can be processed using low cost and low temperature methods on a wide variety of substrates. For example via solution-based processes such as ink-jet printing, doctor blade and spray coating (Fig. 1b). These...