Laser diodes based on solution‐processable materials can benefit numerous technologies including integrated electronics and photonics, telecommunications, and medical diagnostics. An attractive system for implementing these devices is colloidal semiconductor quantum dots (QDs). The progress towards a QD laser diode has been hampered by rapid nonradiative Auger decay of optical‐gain‐active multicarrier states, fast device degradation at high current densities required for laser action, and unfavorable competition between optical gain and optical losses in a multicomponent device stack. Here we resolve some of these challenges and demonstrate optically excited lasing from fully functional high‐current density electroluminescent (EL) devices with an integrated optical resonator. This advance has become possible due to excellent optical gain properties of continuously graded QDs and a refined device architecture, which allows for highly efficient light amplification in a thin, EL‐active QD layer.

In this article, we introduce a method for fabricating highly conductive transparent poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) thin nano-structured film by treating the pristine PEDOT:PSS film with concentrated (55%) hydroiodic acid (HI). HI treatment on the pristine PEDOT:PSS film could significantly reduce the film sheet resistance without sacrificing its transparency and other electronic properties, which are highly desirable for transparent conductors. A thin layer of HI treated PEDOT:PSS film (74 nm) has very high transmittance of 90% and a low sheet resistance of 95 ohm sq⁻¹. The sheet resistance of the film can be reduced to 37 ohm sq⁻¹ by increasing the film thickness but at the expense of its transparency. The low sheet resistance of the film can be attributed to the increase of polarons density, conformational changes and formation of clusters due to removal of some PSS from PEDOT:PSS particles. The results were confirmed by the UV/VIS/near-IR absorption spectroscopy, atomic force microscopy, X-ray photoelectron spectroscopy and energy-dispersive X-ray spectroscopy. Given the high electrical conductivity of the HI treated PEDOT:PSS film, it was then tested as a transparent organic cathode in a polymer solar cell. This ITO-free solar cell showed superior current generation and charge collection with an efficiency of 5.83%, which is 18 times higher than the cell that used untreated PEDOT:PSS film. We, therefore, envisage this potential fabrication method, which uses HI acid, to be applied on other conjugated polymers to enhance their conducting properties for practical applications.

Recent advancements and challenges in scaling up quantum dot light-emitting diodes are highlighted, particularly with respect to the metal oxide nanoparticle and organic electron transport layers.

Graphene oxide (GO) offers comparable efficiency in organic solar cells (OSCs) compared to the hole extraction layer (HEL), poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS), while the shelf lifetime shows a 6-fold increase.

Conducting polymer-grafted InP-based hybrid quantum dots (QDs) show enhanced morphology and optoelectronic properties, resulting in improved efficiency and stability in QD light-emitting diodes using them.