ZKC

The microscopic charge transport and recombination processes behind the widely concerned photoelectric hysteresis in the perovskite solar cell have been investigated with both in situ transient photovoltage/photocurrent measurements and the semiconductor device simulation. Time-dependent behaviors of intensity and direction of the photocurrent and photovoltage are observed under the steady-state bias voltages and open-circuit conditions. These charge processes reveal the electric properties of the cell, demonstrating evolutions of both strength and direction of the internal electric field during the hysteresis. Further calculation indicates that this behavior is mainly attributed to both the interfacial doping and defect effects induced by the ion accumulation, which may be the origins for the general hysteresis in this cell.

Microscopic charge transport and recombination processes behind the widely concerned photoelectric hysteresis in perovskite solar cells are investigated with in situ transient photovoltage and photocurrent measurements, which gives clear information about the internal electric properties of the cell. Further theoretical calculations reveal that both the interfacial doping and defect induced by the ion accumulation are the physical origins for this hysteresis.

Inorganic materials functionalized with organic fluorescent molecules combine advantages of them both, showing potential applications in biomedicine, chemosensors, light-emitting, and so on. However, when more traditional organic dyes are doped into the inorganic materials, the emission of resulting hybrid materials may be quenched, which is not conducive to the efficiency and sensitivity of detection. In contrast to the aggregation-caused quenching (ACQ) system, the aggregation-induced emission luminogens (AIEgens) with high solid quantum efficiency, offer new potential for developing highly efficient inorganic-organic hybrid luminescent materials. So far, many AIEgens have been incorporated into inorganic materials through either physical doping caused by aggregation induced emission (AIE) or chemical bonding (e.g., covalent bonding, ionic bonding, and coordination bonding) caused by bonding induced emission (BIE) strategy. The hybrid materials exhibit excellent photoactive properties due to the intramolecular motion of AIEgens is restricted by inorganic matrix. Recent advances in the fabrication of AIEgens-functionalized inorganic-organic hybrid materials and their applications in biomedicine, chemical sensing, and solid-state light emitting are presented.

Aggregation-induced emission luminogens functionalized with inorganic-organic hybrid materials combine the benefits of inorganic and organic components, showing significant advantages in tunable emission, excellent biocompatibility, bright fluorescence, high photostability, and facile surface functionalization, which can be used as efficient fluorescent probes in biomedicine, chemical sensing, and solid-state light emitting.

Organic–inorganic lead halide perovskite materials have recently attracted much attention in the field of optoelectronic devices. Here, a hybrid piezoelectric nanogenerator based on a composite of piezoelectric formamidinium lead halide perovskite (FAPbBr₃) nanoparticles and polydimethylsiloxane polymer is fabricated. Piezoresponse force spectroscopy measurements reveal that the FAPbBr₃ nanoparticles contain well-developed ferroelectric properties with high piezoelectric charge coefficient (d₃₃) of 25 pmV⁻¹. The flexible device exhibits high performance with a maximum recordable piezoelectric output voltage of 8.5 V and current density of 3.8 μA cm⁻² under periodically vertical compression and release operations. The alternating energy generated from nanogenerators can be used to charge a capacitor and light up a red light-emitting diode through a bridge rectifier. This result innovatively expands the feasibility of organic–inorganic lead halide perovskite materials for application in a wide variety of high-performance energy harvesting devices.

The hybrid piezoelectric nanogenerators based on a composite of piezoelectric organic–inorganic lead halide perovskite materials and polydimethylsiloxane polymer are demonstrated. The recordable maximum piezoelectric output voltage and current density up to 8.5 V and 3.8 μA cm⁻² are successfully obtained under periodically vertical compression.

Enhanced metal oxide (In₂O₃, IZO, IGZO) transistor performance via polyethylenimine (PEI) doping is demonstrated by J. Yu, M. J. Bedzyk, T. J. Marks, A. Fachetti, and co-workers on page 6179. PEI electron donating capacity combined with charge trapping and variation in the matrix film microstructure contribute, for proper PEI doping levels, to high electron mobility, optimal TFT off-currents, and optimal threshold voltages. This concept is promising for opto-electronic devices based on metal oxide films.

Perovskite solar cells (PSCs) are demonstrating great potential to compete with second generation photovoltaics. Nevertheless, the key issue hindering PSCs full exploitation relies on their stability. Among the strategies devised to overcome this problem, the use of carbon nanostructures (CNSs) as hole transporting materials (HTMs) has given impressive results in terms of solar cells stability to moisture, air oxygen, and heat. Here, the use of a HTM based on a poly(3-hexylthiophene) (P3HT) matrix doped with organic functionalized single walled carbon nanotubes (SWCNTs) and reduced graphene oxide in PSCs is proposed to achieve higher power conversion efficiencies (η = 11% and 7.3%, respectively) and prolonged shelf-life stabilities (480 h) in comparison with a benchmark PSC fabricated with a bare P3HT HTM (η = 4.3% at 480 h). Further endurance test, i.e., up to 3240 h, has shown the failure of all the PSCs based on undoped P3HT, while, on the contrary, a η of ≈8.7% is still detected from devices containing 2 wt% SWCNT-doped P3HT as HTM. The increase in photovoltaic performances and stabilities of the P3HT-CNS-based solar cell, with respect to the standard P3HT-based one, is attributed to the improved interfacial contacts between the doped HTM and the adjacent layers.

Improved photovoltaic efficiencies and stabilities over prolonged times are demonstrated for perovskite solar cells based on a poly-3(hexylthiophene) layer doped with organic functionalized single-walled carbon nanotubes and reduced graphene oxide with respect to a reference device based on the undoped polymer.

A small-molecular acceptor, tetraphenylpyrazine-perylenediimide tetramer (TPPz-PDI₄), which has a reduced extent of intramolecular twisting compared to two other small-molecular acceptors is designed. Benefiting from the lowest extent of intramolecular twisting, TPPz-PDI₄ exhibits the highest aggregation tendency and electron mobility, and therefore achieves a highest power conversion efficiency of 7.1%.

The origin of hysteresis behavior is probed in perovskite solar cells (PSCs) with simultaneous measurements of cell open circuit voltage (V_oc) and photoluminescence intensity over time following illumination of the cell. It is shown, for the first time, that the transient changes in terminal voltage and luminescent intensity do not follow the relationship that would be predicted by the generalized Plank radiation law. A mechanism is proposed based on the presence of a resistive barrier to majority carrier flow at the interface between the perovskite film and the electron or hole transport layer, in combination with significant interface recombination. This results in a decoupling of the internal quasi-Fermi level separation and the externally measured voltage. A simple numerical model is used to provide in-principle validation for the proposed mechanism and it is confirmed that mobile ionic species are a likely candidate for creating the time-varying majority carrier bottleneck by its reduced conductivity. The findings show that the V_oc of PSCs may be lower than the limit imposed by the cell luminescence efficiency, even under steady-state conditions.

The origin of hysteresis behavior in perovskite solar cells is probed with simultaneous measurements of cell open circuit voltage and photoluminescence intensity over time following illumination of the cell. The findings demonstrate the existence of a resistive barrier to majority carrier flow at the interfaces of these devices, in combination with significant interface recombination.