Efficient Near-Infrared PbS Quantum Dot Solar Cells Employing Hydrogenated In2 O3 Transparent Electrode

Colloidal quantum dot materials for next-generation near-infrared optoelectronics

Colloidal quantum dots (CQDs) are a promising class of materials for next-generation optoelectronic devices, such as displays, LEDs, lasers, photodetectors, and solar cells. CQDs can be obtained at low cost and in large quantities using wet chemistry. CQDs have also been produced using various materials, such as CdSe, InP, perovskites, PbS, PbSe, and InAs. Some of these CQD materials absorb and emit photons in the visible region, making them excellent candidates for displays and LEDs, while others interact with low-energy photons in the near-infrared (NIR) region and are intensively utilized in NIR lasers, NIR photodetectors, and solar cells. In this review, we have focused on NIR CQD materials and reviewed the development of CQD materials for solar cells, NIR lasers, and NIR photodetectors since the first set of reports on CQD materials in these particular applications.

Flexible, Transparent and Conductive Metal Mesh Films with Ultra-High FoM for Stretchable Heating and Electromagnetic Interference Shielding

Despite the growing demand for transparent conductive films in smart and wearable electronics for electromagnetic interference (EMI) shielding, achieving a flexible EMI shielding film, while maintaining a high transmittance remains a significant challenge. Herein, a flexible, transparent, and conductive copper (Cu) metal mesh film for EMI shielding is fabricated by self-forming crackle template method and electroplating technique. The Cu mesh film shows an ultra-low sheet resistance (0.18 Ω □-1), high transmittance (85.8%@550 nm), and ultra-high figure of merit (> 13,000). It also has satisfactory stretchability and mechanical stability, with a resistance increases of only 1.3% after 1,000 bending cycles. As a stretchable heater (ε > 30%), the saturation temperature of the film can reach over 110 °C within 60 s at 1.00 V applied voltage. Moreover, the metal mesh film exhibits outstanding average EMI shielding effectiveness of 40.4 dB in the X-band at the thickness of 2.5 μm. As a demonstration, it is used as a transparent window for shielding the wireless communication electromagnetic waves. Therefore, the flexible and transparent conductive Cu mesh film proposed in this work provides a promising candidate for the next-generation EMI shielding applications.

Insight into the High Mobility and Stability of In2 O3 :H Film

Wide bandgap semiconductors, particularly In2 O3 :Sn (ITO), are widely used as transparent conductive electrodes in optoelectronic devices. Nevertheless, due to the strohave beenng scattering probability of high-concentration oxygen vacancy (VO ) defects, the mobility of ITO is always lower than 40 cm2  V-1  s-1 . Recently, hydrogen-doped In2 O3 (In2 O3 :H) films have been proven to have high mobility (>100 cm2  V-1  s-1 ), but the origin of this high mobility is still unclear. Herein, a high-resolution electron microscope and theoretical calculations are employed to investigate the atomic-scale mechanisms behind the high carrier mobility in In2 O3 :H films. It is found that VO can cause strong lattice distortion and large carrier scattering probability, resulting in low carrier mobility. Furthermore, hydrogen doping can simultaneously reduce the concentration of VO , which accounts for high carrier mobility. The thermal stability and acid-base corrosion mechanism of the In2 O3 :H film are investigated and found that hydrogen overflows from the film at high temperatures (>250 °C), while acidic or alkaline environments can cause damage to the In2 O3 grains themselves. Overall, this work provides insights into the essential reasons for high carrier mobility in In2 O3 :H and presents a new research approach to the doping and stability mechanisms of transparent conductive oxides.

Optical engineering of infrared PbS CQD photovoltaic cells for wireless optical power transfer systems

Infrared photovoltaic cells (IRPCs) have attracted considerable attention for potential applications in wireless optical power transfer (WOPT) systems. As an efficient fiber-integrated WOPT system typically uses a 1550 nm laser beam, it is essential to tune the peak conversion efficiency of IRPCs to this wavelength. However, IRPCs based on lead sulfide (PbS) colloidal quantum dots (CQDs) with an excitonic peak of 1550 nm exhibit low short circuit current (J_sc) due to insufficient absorption under monochromatic light illumination. Here, we propose comprehensive optical engineering to optimize the device structure of IRPCs based on PbS CQDs, for 1550 nm WOPT systems. The absorption by the device is enhanced by improving the transmittance of tin-doped indium oxide (ITO) in the infrared region and by utilizing the optical resonance effect in the device. Therefore, the optimized device exhibited a high short circuit current density of 37.65 mA/cm² under 1 sun (AM 1.5G) solar illumination and 11.91 mA/cm² under 1550 nm illumination 17.3 mW/cm². Furthermore, the champion device achieved a record high power conversion efficiency (PCE) of 7.17% under 1 sun illumination and 10.29% under 1550 nm illumination. The PbS CQDs IRPCs under 1550 nm illumination can even light up a liquid crystal display (LCD), demonstrating application prospects in the future.

Cerium-Doped Indium Oxide as a Top Electrode of Semitransparent Perovskite Solar Cells

Semitransparent perovskite solar cells (ST-PSCs) play a very important role in high-efficiency tandem solar cells and building integrated photovoltaics (BIPV). One of the main challenges for high-performance ST-PSCs is to obtain suitable top-transparent electrodes by appropriate methods. Transparent conductive oxide (TCO) films, as the most widely used transparent electrodes, are also adopted in ST-PSCs. However, the possible ion bombardment damage during the TCO deposition and the relatively high postannealing temperature usually required for high-quality TCO films is not conducive to improving the performance of the perovskite solar cells with low ion bombardment and temperature tolerances. Herein, cerium-doped indium oxide (ICO) thin films are prepared by reactive plasma deposition (RPD) at substrate temperatures below 60 °C. A high carrier mobility of 50.26 cm² V^-1 s^-1, a low resistivity of 7.18 × 10^-4 Ω·cm, and an average transmittance of 86.53% in the wavelength range of 400-800 nm and 87.37% in the wavelength range of 800-1200 nm are achieved. The RPD-prepared ICO film is used as a transparent electrode on top of the ST-PSCs (band gap ∼1.68 eV), and photovoltaic conversion efficiency (PCE) of 18.96% is achieved on the champion device.