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

Self-powered deep-ultraviolet photodetectors have received considerable attention in recent years because of their efficiency, reliability, and various applications in civilian and military fields. Herein, a Ag/Ag2O layer is continuously deposited on a β-Ga2O3 epitaxial layer by a facing target sputtering system without opening the chamber, which has an advantage in time and cost. A p-n junction photodetector was constructed through the Ag2O/β-Ga2O3 heterojunction and by varying the thickness of the Ag film, which was controlled by the sputtering time. The effect of top electrode thickness on the photoresponse characteristics of photodetectors was studied. Because thin Ag films have low surface roughness, indicating low optical loss and good interfacial conditions, photodetectors using a thin Ag film as the top electrode exhibit high photoresponsivity. However, Ag films that were thinner than the threshold thickness, which is the minimum thickness required to form a continuous, homogeneous surface film, exhibited rather low performance owing to the high reflection and scattering caused by the inhomogeneous surface morphology. The as-fabricated photodetector with a 20 nm Ag film presents a high on/off ratio of 3.43 × 108, responsivity and detectivity of 25.65 mA/W and 6.10 × 1011 Jones, respectively, and comparable rise and decay times of 108 and 80 ms, respectively. Additionally, even after three months of storage in an ambient environment, the photoresponse of the photodetector was maintained, indicating good stability in air. These results suggest that Ag2O/β-Ga2O3 heterojunction-based photodetectors with thin Ag films can be used in various applications requiring deep-ultraviolet detection without an external power supply.

Ag2O/β-Ga2O3 Heterojunction-Based Self-Powered Solar Blind Photodetector with High Responsivity and Stability.

https://iopscience.iop.org/article/10.1088/1361-6463/aa9357/pdf

Enhanced electrical stability of nitrate ligand-based hexaaqua complexes solution-processed ultrathin a-IGZO transistors

Indium-gallium-zinc oxide- and zinc oxynitride-based heterojunction phototransistors were successfully demonstrated to control the persistent photoconduction (PPC) effect and be also responded sensitively at the range from visible to near-infrared. ZnON plays a key role in extending the spectral response at various frequencies of operation. The devices show significantly different photoresponse and photorecovery characteristics depending on the number of stacked layers of IGZO and ZnON. After negative bias and illumination stress was applied to the devices for 1 h, tandem-structure-based phototransistors recovered remarkably better than single-component IGZO devices. We suggest that the improvements to photoresponse and photorecovery result from the presence of potential wells between two IGZO layers and the energy band alignment of the tandem structure.

You Seung Rim

Papers

Ag2O/β-Ga2O3 Heterojunction-Based Self-Powered Solar Blind Photodetector with High Responsivity and Stability.

Enhanced electrical stability of nitrate ligand-based hexaaqua complexes solution-processed ultrathin a-IGZO transistors

Reduction of Persistent Photoconduction with IGZO/ZnON-Tandem-Structure Visible-Near-Infrared Phototransistors.

Characteristics of indium zinc oxide films deposited using the facing targets sputtering method for OLEDs applications

Deep-level defect distribution as a function of oxygen partial pressure in sputtered ZnO thin-film transistors