High-Performance Transparent Conducting Metal Network Electrodes for Perovksite Photodetectors

Transparent conducting electrodes with high transparency and conductivity are necessary components for optoelectronic devices. In this work, a facile wet-chemical lift-off process is first introduced to fabricate Au network flexible transparent electrodes with electrospun polymer fiber network as mask. Low resistance (5.18 Ω sq^–1) of the transparent electrode was obtained when the transparency was around 90%, which was comparable to the state-of-the-art transparent electrodes. Low root-mean-square roughness of 23 nm was obtained when the Au nanowire thickness was 30 nm. The perovskite CH₃NH₃PbI₃ photodetector based on the 30 nm thick Au network electrode shows a large linear dynamic range of 138 dB, a high detectivity over 10¹² Jones, and better flexibility than that based on the commercial indium tin oxide electrode, which demonstrates that the Au network electrode is a promising flexible transparent conducting electrode for optoelectronic devices

Study on the Ambient Temperature as an Important but Easily Neglected Factor in the Process of Preparing Photovoltaic All-Inorganic CsPbIBr₂ Perovskite Film by the Elegant Solvent-Controlled Growth Strategy

All-inorganic CsPbIBr2 perovskite has received extensive attention in the field of solar cells due to its good wet and thermal stability as well as a moderate band gap. In the preparation of CsPbIBr2 film by one-step spin-coating method, the amount of dimethyl sulfoxide solvent remaining in the precursor film has a great influence on the process of film growth. Therefore, it is necessary to ensure that an appropriate amount of solvent exists in the precursor film before annealing. Herein, we adopted the solvent-controlled growth (SCG) strategy, that is, standing by the precursor films in the nitrogen glovebox for a period of time before annealing, to make sure that excess solvent can be evaporated from the precursor film. In this work, we found that the ambient temperature is an important but easily neglected factor in the process of preparing CsPbIBr2 film by the SCG strategy. When the ambient temperature is 20 °C, SCG treatment is required to obtain a flat and dense CsPbIBr2 film. However, SCG treatment is not essential at 30 °C. The ambient temperature has an impact on the evaporation rate of the solvent in the precursor film, and thus affects the effect of the SCG strategy. This work highlights that, when preparing CsPbIBr2 film by a one-step spin-coating method, in order to obtain a high-quality CsPbIBr2 film, the influence of ambient temperature on solvent-controlled growth strategy should be considered

Nucleation and Crystal Growth of Organic–Inorganic Lead Halide Perovskites under Different Relative Humidity

Organic–inorganic lead halide perovskite compounds are very promising materials for high-efficiency perovskite solar cells. But how to fabricate high-quality perovksite films under controlled humidity conditions is still an important issue due to their sensitivity to moisture. In this study, we investigated the influence of ambient humidity on crystallization and surface morphology of one-step spin-coated perovskite films, as well as the performance of solar cells based on these perovskite films. On the basis of experimental analyses and thin film growth theory, we conclude that the influence of ambient humidity on nucleation at spin-coating stage is quite different from that on crystal growth at annealing stage. At the spin-coating stage, high nucleation density induced by high supersaturation prefers to appear under anhydrous circumstances, resulting in layer growth and high coverage of perovskite films. But at the annealing stage, the modest supersaturation benefits formation of perovskite films with good crystallinity. The films spin-coated under low relative humidity (RH) followed by annealing under high RH show an increase of crystallinity and improved performance of devices. Therefore, a mechanism of fast nucleation followed by modest crystal growth (high supersaturation at spin-coating stage and modest supersaturation at annealing stage) is suggested in the formation of high-quality perovskite films

Highly Flexible Self-Powered Organolead Trihalide Perovskite Photodetectors with Gold Nanowire Networks as Transparent Electrodes

Organolead trihalide perovskites (OTPs) such as CH₃NH₃PbI₃ (MAPbI₃) have attracted much attention as the absorbing layer in solar cells and photodetectors (PDs). Flexible OTP devices have also been developed. Transparent electrodes (TEs) with higher conductivity, stability, and flexibility are necessary to improve the performance and flexibility of flexible OTP devices. In this work, patterned Au nanowire (AuNW) networks with high conductivity and stability are prepared and used as TEs in self-powered flexible MAPbI₃ PDs. These flexible PDs show peak external quantum efficiency and responsivity of 60% and 321 mA/W, which are comparable to those of MAPbI₃ PDs based on ITO TEs. The linear dynamic range and response time of the AuNW-based flexible PDs reach ∼84 dB and ∼4 μs, respectively. Moreover, they show higher flexibility than ITO-based devices, around 90%, and 60% of the initial photocurrent can be retained for the AuNW-based flexible PDs when bent to radii of 2.5 and 1.5 mm. This work suggests a high-performance, highly flexible, and stable TE for OTP flexible devices

Enhanced Performance of Photoelectrochemical Water Splitting with ITO@α-Fe₂O₃ Core–Shell Nanowire Array as Photoanode

Hematite (α-Fe₂O₃) is one of the most promising candidates for photoelectrodes in photoelectrochemical water splitting system. However, the low visible light absorption coefficient and short hole diffusion length of pure α-Fe₂O₃ limits the performance of α-Fe₂O₃ photoelectrodes in water splitting. Herein, to overcome these drawbacks, single-crystalline tin-doped indium oxide (ITO) nanowire core and α-Fe₂O₃ nanocrystal shell (ITO@α-Fe₂O₃) electrodes were fabricated by covering the chemical vapor deposited ITO nanowire array with compact thin α-Fe₂O₃ nanocrystal film using chemical bath deposition (CBD) method. The <i>J</i>–<i>V</i> curves and IPCE of ITO@α-Fe₂O₃ core–shell nanowire array electrode showed nearly twice as high performance as those of the α-Fe₂O₃ on planar Pt-coated silicon wafers (Pt/Si) and on planar ITO substrates, which was considered to be attributed to more efficient hole collection and more loading of α-Fe₂O₃ nanocrystals in the core–shell structure than planar structure. Electrochemical impedance spectra (EIS) characterization demonstrated a low interface resistance between α-Fe₂O₃ and ITO nanowire arrays, which benefits from the well contact between the core and shell. The stability test indicated that the prepared ITO@α-Fe₂O₃ core–shell nanowire array electrode was stable under AM1.5 illumination during the test period of 40 000 s

<i>In Situ</i> Fabrication of Highly Conductive Metal Nanowire Networks with High Transmittance from Deep-Ultraviolet to Near-Infrared

We have developed a facile and compatible method to <i>in situ</i> fabricate uniform metal nanowire networks on substrates. The as-fabricated metal nanowire networks show low sheet resistance and high transmittance (2.2 Ω sq^–1 at <i>T</i> = 91.1%), which is equivalent to that of the state-of-the-art metal nanowire networks. We demonstrated that the transmittance of the metal networks becomes homogeneous from deep-ultraviolet (200 nm) to near-infrared (2000 nm) when the size of the wire spacing increases to micrometer size. Theoretical and experimental analyses indicated that we can improve the conductivity of the metal networks as well as keep their transmittance by increasing the thickness of the metal films. We also carried out durability tests to demonstrate our as-fabricated metal networks having good flexibility and strong adhesion