Organic photodetectors (OPDs) based on non‐fullerene acceptors (NFAs) have received considerable attention because of their potential for use in various commercial applications as near‐infrared (NIR) light sensing platforms. However, recent OPDs suffer from low NIR photoresponse and large dark/noise currents with narrow bandgap organic photoactive materials. Herein, a π‐bridge molecular engineering strategy replacing alkoxythienyl with benzothiadiazole for ultra‐narrow bandgap (ultra‐NBG) NFAs is designed to achieve simultaneously high photoresponse at NIR region and low noise current density, thereby leading to excellent NIR (≈1050 nm) detectivity (D^*). The newly synthesized ultra‐NBG NFAs, namely COB and CBT with optical bandgaps below 1.14 eV, present high responsivity (R) with 0.369 and 0.080 A W⁻¹, respectively, at a wavelength of 1050 nm. Especially, with effectively suppressed noise current density, COB‐based OPD exhibits a high NIR (≈1050 nm) D^* value of 2.18 × 10¹¹ cm Hz^1/2 W⁻¹ at −0.5 V bias. The obtained R and D^* values for these NFAs exceed or are comparable to those of a commercial Si photodetector at 1050 nm. This work provides important insight into the π‐bridge molecular engineering strategy for ultra‐NBG NFAs, which facilitate achieving highly sensitive NIR OPDs with high NIR photoresponse and low dark/noise current.

Organic-inorganic hybrid perovskite materials have attracted tremendous attention as a key material in various optoelectronic devices. Distinctive optoelectronic properties, such as a tunable energy band position, long carrier diffusion lengths, and high charge carrier mobility, have allowed rapid progress in various perovskite-based optoelectronic devices (solar cells, photodetectors, light emitting diodes (LEDs), and lasers). Interestingly, the developments of each field are based on different characteristics of perovskite materials which are suitable for their own applications. In this review, we provide the fundamental properties of perovskite materials and categorize the usages in various optoelectronic applications. In addition, the prerequisite factors for those applications are suggested to understand the recent progress of perovskite-based optoelectronic devices and the challenges that need to be solved for commercialization.

Quasi-type II heterostructured nanocrystals (NCs) have been of particular interest due to their great potential for controlling the interplay of charge carriers. However, the lack of material choices for quasi-type II NCs restricts the accessible emission wavelength from red to near-infrared (NIR), which hinders their use in light-emitting applications that demand a wide range of visible colors. Herein, we demonstrate a new class of quasi-type II nanoemitters formulated in ZnSe/ZnSe _{1- X} Te _X /ZnSe seed/spherical quantum well/shell heterostructures (SQWs) whose emission wavelength ranges from blue to orange. In a given geometry, ZnSe _{1- X} Te _X emissive layers grown between the ZnSe seed and the shell layer are strained to fit into the surrounding media, and thus, the lattice mismatch between ZnSe _{1- X} Te _X and ZnSe is effectively alleviated. In addition, composition of the ZnSe _{1- X} Te _X emissive layer and the dimension of the ZnSe shell layer are engineered to tailor the distribution and energy of electron and hole wave functions. Benefitting from the capabilities to tune the charge carriers on demand and to form defect-free heterojunctions, ZnSe/ZnSe _{1- X} Te _X /ZnSe/ZnS NCs show near-unity photoluminescence quantum yield ( PL QY > 90 % ) in a broad range of emission wavelengths (peak PL from 450 nm to 600 nm). Finally, we exemplify dichromatic white NC-based light-emitting diodes (NC-LEDs) employing the mixed layer of blue- and yellow-emitting ZnSe/ZnSe _{1- X} Te _X /ZnSe/ZnS SQW NCs.

Recently, a significant breakthrough in emerging photovoltaics occurred. Now, perovskite solar cells, hybrid types of organic and inorganic solar cells, are considered as reliable next-generation solar cells due to their outstanding photovoltaic performance. Records of the National Renewable Energy Laboratory (NREL) on cell efficiency research indicates a prominent growth in the power conversion efficiency (PCE) of a perovskite solar cells which is now approaching 20.1%. Perovskite solar cells are, in general, classified into three types based on their structures; the mesoporous type with TiO₂ nanoparticles, the meso-superstructure type with Al₂O₃ and the planar hetero-junction type. Among them, planar-structured perovskite solar cells have strong advantages due to their easy processibility and flexibility. We can replace the materials in the electron transport layer (ETL) and the hole transport layer (HTL) with common materials that are available in organic solar cells. However, a great challenge is to fabricate a high-quality perovskite film because the perovskite morphology is highly sensitive to its fabrication conditions. For control of the film’s morphology, some experiments, such as changing the annealing temperature or time and adding some additives, have been done to increase the surface coverage of perovskite films. In this work, we introduce normal, planar, perovskite solar cells with a hetero-junction structure based on compact TiO₂ and a mixed halide perovskite (CH₃NH₃PbI_3−x Cl _x ). To enlarge the surface coverage of perovskite film, we used an UV-ozone treatment on top of the compact TiO₂, which made the surface of TiO₂ hydrophilic. Because a perovskite precursor is hydrophilic, an UV-ozone treatment is expected to improve the wettability between the compact TiO₂ and the perovskite film. Here, we present the photovoltaic performance, along with the surface coverage difference, for various UV-ozone treatment time. In addition, the effect of the UV-ozone treatment was examined by using an opto-electronic analysis.