The formation of a dense and uniform thin layer on the substrates is crucial for the fabrication of high-performance perovskite solar cells (PSCs) containing formamidinium with multiple cations and mixed halide anions. The concentration of defect states, which reduce a cell’s performance by decreasing the open-circuit voltage and short-circuit current density, needs to be as low as possible. We show that the introduction of additional iodide ions into the organic cation solution, which are used to form the perovskite layers through an intramolecular exchanging process, decreases the concentration of deep-level defects. The defect-engineered thin perovskite layers enable the fabrication of PSCs with a certified power conversion efficiency of 22.1% in small cells and 19.7% in 1-square-centimeter cells.

Iodide management in formamidinium-lead-halide–based perovskite layers for efficient solar cells

Transparent electronics is today one of the most advanced topics for a wide range of device applications. The key components are wide bandgap semiconductors, where oxides of different origins play an important role, not only as passive component but also as active component, similar to what is observed in conventional semiconductors like silicon. Transparent electronics has gained special attention during the last few years and is today established as one of the most promising technologies for leading the next generation of flat panel display due to its excellent electronic performance. In this paper the recent progress in n- and p-type oxide based thin-film transistors (TFT) is reviewed, with special emphasis on solution-processed and p-type, and the major milestones already achieved with this emerging and very promising technology are summarizeed. After a short introduction where the main advantages of these semiconductors are presented, as well as the industry expectations, the beautiful history of TFTs is revisited, including the main landmarks in the last 80 years, finishing by referring to some papers that have played an important role in shaping transparent electronics. Then, an overview is presented of state of the art n-type TFTs processed by physical vapour deposition methods, and finally one of the most exciting, promising, and low cost but powerful technologies is discussed: solution-processed oxide TFTs. Moreover, a more detailed focus analysis will be given concerning p-type oxide TFTs, mainly centred on two of the most promising semiconductor candidates: copper oxide and tin oxide. The most recent data related to the production of complementary metal oxide semiconductor (CMOS) devices based on n- and p-type oxide TFT is also be presented. The last topic of this review is devoted to some emerging applications, finalizing with the main conclusions. Related work that originated at CENIMAT|I3N during the last six years is included in more detail, which has led to the fabrication of high performance n- and p-type oxide transistors as well as the fabrication of CMOS devices with and on paper.

Oxide Semiconductor Thin‐Film Transistors: A Review of Recent Advances

Lead halide perovskite solar cells have recently attracted tremendous attention because of their excellent photovoltaic efficiencies. However, the poor stability of both the perovskite material and the charge transport layers has so far prevented the fabrication of devices that can withstand sustained operation under normal conditions. Here, we report a solution-processed lead halide perovskite solar cell that has p-type NiOx and n-type ZnO nanoparticles as hole and electron transport layers, respectively, and shows improved stability against water and oxygen degradation when compared with devices with organic charge transport layers. Our cells have a p–i–n structure (glass/indium tin oxide/NiOx/perovskite/ZnO/Al), in which the ZnO layer isolates the perovskite and Al layers, thus preventing degradation. After 60 days storage in air at room temperature, our all-metal-oxide devices retain about 90% of their original efficiency, unlike control devices made with organic transport layers, which undergo a complete degradation after just 5 days. The initial power conversion efficiency of our devices is 14.6 ± 1.5%, with an uncertified maximum value of 16.1%. Using metal oxides for both the hole- and electron-transport layers in perovskite solar cells significantly improves their stability compared with devices containing organic transport layers.

Improved air stability of perovskite solar cells via solution-processed metal oxide transport layers

Optical transparency, tunable conducting properties and easy processability make metal oxides key materials for advanced optoelectronic devices. This Review discusses recent advances in the synthesis of these materials and their use in applications. Metal oxides (MOs) are the most abundant materials in the Earth's crust and are ingredients in traditional ceramics. MO semiconductors are strikingly different from conventional inorganic semiconductors such as silicon and III–V compounds with respect to materials design concepts, electronic structure, charge transport mechanisms, defect states, thin-film processing and optoelectronic properties, thereby enabling both conventional and completely new functions. Recently, remarkable advances in MO semiconductors for electronics have been achieved, including the discovery and characterization of new transparent conducting oxides, realization of p-type along with traditional n-type MO semiconductors for transistors, p–n junctions and complementary circuits, formulations for printing MO electronics and, most importantly, commercialization of amorphous oxide semiconductors for flat panel displays. This Review surveys the uniqueness and universality of MOs versus other unconventional electronic materials in terms of materials chemistry and physics, electronic characteristics, thin-film fabrication strategies and selected applications in thin-film transistors, solar cells, diodes and memories.

Metal oxides for optoelectronic applications

Methylammonium Chloride Induces Intermediate Phase Stabilization for Efficient Perovskite Solar Cells

5 mm-scale large FAPbI 3 single crystals and corresponding photoconductive properties are shown. The phase transition of FAPbI3 between the α-phase and δ-phase is studied. The carrier mobility is 4.4 cm(2) V(-1) s(-1) with a lifetime of 484 ns in the bulk of the single crystal. Finally, photodetectors based on single-crystal FAPbI3 are demonstrated.

Single Crystal Formamidinium Lead Iodide (FAPbI3): Insight into the Structural, Optical, and Electrical Properties.

Printable electronics present a new era of wearable electronic technologies. Detailed technologies consisting of novel ink semiconductor materials, flexible substrates, and unique processing methods can be integrated to create flexible sensors. To detect various stimuli of the human body, as well as specific environments, unique electronic devices formed by "ink-based semiconductors" onto flexible and/or stretchable substrates have become a major research trend in recent years. Materials such as inorganic, organic, and hybrid semiconductors with various structures (i.e., 1D, 2D and 3D) with printing capabilities have been considered for bio and medical applications. In this review, we report recent progress in materials and devices for future wearable sensor technologies.

Recent Progress in Materials and Devices toward Printable and Flexible Sensors

Detection of analytes by means of field-effect transistors bearing ligand-specific receptors is fundamentally limited by the shielding created by the electrical double layer (the "Debye length" limitation). We detected small molecules under physiological high-ionic strength conditions by modifying printed ultrathin metal-oxide field-effect transistor arrays with deoxyribonucleotide aptamers selected to bind their targets adaptively. Target-induced conformational changes of negatively charged aptamer phosphodiester backbones in close proximity to semiconductor channels gated conductance in physiological buffers, resulting in highly sensitive detection. Sensing of charged and electroneutral targets (serotonin, dopamine, glucose, and sphingosine-1-phosphate) was enabled by specifically isolated aptameric stem-loop receptors.

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Aptamer–field-effect transistors overcome Debye length limitations for small-molecule sensing

Novel structure-engineered amorphous oxide semiconductor thin-film transistors using a solution process to overcome the trade-off between high mobility and other parameters (i.e., on/off ratio, sub-threshold voltage swing, threshold voltage, and so on) are proposed. High performance confining structure-engineered AOS TFTs are successfully demonstrated, which utilize a specially designed layer with ultra-high density and high electron mobility.

Boost up mobility of solution-processed metal oxide thin-film transistors via confining structure on electron pathways

Thin-film transistors (TFTs) with a ZrZnSnO (ZZTO) channel layer were fabricated using a solution process. As-prepared ZnSnO (ZTO) TFTs had a large off-current. However, as the content of Zr ions increased in ZTO, the threshold voltage shifted, and the off-current in the TFTs decreased. Because Zr has a lower standard electrode potential, it is more readily oxidized than Sn or Zn. Thus, Zr acted as an effective carrier suppressor in the ZTO system and a ZZTO TFT with a high mobility of a 4.02 cm2 V−1 s−1 and a large on/off ratio of over 106 was achieved.

You Seung Rim

Papers

Single Crystal Formamidinium Lead Iodide (FAPbI3): Insight into the Structural, Optical, and Electrical Properties.

Recent Progress in Materials and Devices toward Printable and Flexible Sensors

Aptamer–field-effect transistors overcome Debye length limitations for small-molecule sensing

Boost up mobility of solution-processed metal oxide thin-film transistors via confining structure on electron pathways

Effect of Zr addition on ZnSnO thin-film transistors using a solution process