Regulation of Quantum Wells Width Distribution in Quasi-2D Perovskite Films for High-Performance Photodetectors.

Dynamic optimization of the quantum-well (QW) width distribution in quasi-2D halide perovskite thin films is an effective approach for tuning the properties of photoelectric devices. Here, that the QWs width distribution in quasi-2D perovskite films can be controlled only by using hydroiodic acid (HI) as an additive is demonstrated. A uniform distribution of the colloidal particle size in the quasi-2D perovskite precursor solution is achieved through the formation of soluble iodoplumbate coordination complexes, PbI3 - from the reaction of HI with PbI2 , resulting in an improved phase purity in the final film. Density functional theory calculations indicate that the ideal n value quasi-2D perovskite reaction pathway through the PbI3 - complex has a lower enthalpy of formation than the random nucleation pathway without the HI additive. Benefiting from this merit, a high-quality quasi-2D perovskite film with optimized phase purity delivered a balanced carrier diffusion length and improved carrier mobility. The resultant photodetectors exhibited a light on/off ratio of 50 000, a responsivity of 0.96 A W-1 , and a detectivity of 5.7 × 1012 Jones at 532 nm. In addition, the state-of-the-art device maintained more than 80% of its initial photocurrent after 720 h of storage at 30% relative humidity.

Dredging the Charge-Carrier Transfer Pathway for Efficient Low-Dimensional Ruddlesden-Popper Perovskite Solar Cells.

Low-dimensional Ruddlesden-Popper (LDRP) perovskites still suffer from inferior carrier transport properties. Here, we demonstrate that efficient exciton dissociation and charge transfer can be achieved in LDRP perovskite by introducing γ-aminobutyric acid (GABA) as a spacer. The hydrogen bonding links adjacent spacing sheets in (GABA)2 MA3 Pb4 I13 (MA=CH3 NH3 + ), leading to the charges localized in the van der Waals gap, thereby constructing "charged-bridge" for charge transfer through the spacing region. Additionally, the polarized GABA weakens dielectric confinement, decreasing the (GABA)2 MA3 Pb4 I13 exciton binding energy as low as ≈73 meV. Benefiting from these merits, the resultant GABA-based solar cell yields a champion power conversion efficiency (PCE) of 18.73 % with enhanced carrier transport properties. Furthermore, the unencapsulated device maintains 92.8 % of its initial PCE under continuous illumination after 1000 h and only lost 3 % of its initial PCE under 65 °C for 500 h.

Pen-writing high-quality perovskite films and degradable optoelectronic devices.

Paper is ubiquitous in the daily life and has been widely used for writing and drawing because of their low-cost, widely accessible, and degradable properties. However, simple ways to fabricate paper-based optoelectronic devices remain a great challenge. In this work, we report a facile method to fabricate high-quality perovskite films and optoelectronic devices on paper by direct pen-writing. Through introducing seed layers on papers, planar-integrated single-crystal perovskite films are easily prepared using commercial pens. Based on such a simple and convenient method, perovskite photodetector arrays and image sensors with graphite electrodes are fabricated on paper, and show satisfactory performances. This method provides a simple and effective approach for preparation of paper-based perovskite devices. It will be of significance for the development of degradable optoelectronic devices.

Conjuncted Pyro-Piezoelectric Effect for Self-Powered Simultaneous Temperature and Pressure Sensing.

Ferroelectric materials use both the pyroelectric effect and piezoelectric effect for energy conversion. A ferroelectric BaTiO3 -based pyro-piezoelectric sensor system is demonstrated to detect temperature and pressure simultaneously. The voltage signal of the device is found to enhance with increasing temperature difference with a sensitivity of about 0.048 V °C-1 and with applied pressure with a sensitivity of about 0.044 V kPa-1 . Moreover, no interference appears in the output voltage signals when piezoelectricity and pyroelectricity are conjuncted in the device. A novel 4 × 4 array sensor system is developed to sense real-time temperature and pressure variations induced by a finger. This system has potential applications in machine intelligence and man-machine interaction.