Moisture‐Triggered Self‐Healing Flexible Perovskite Photodetectors with Excellent Mechanical Stability

Abstract

low-temperature solution method, which makes it a promising candidate for flexible devices. [19][20][21][22][23] Novel devices based on perovskite have proven great potential for further application. [24][25][26] However, perovskites are very sensitive to air moisture which invades cracks of flexible films and accelerates the damage to devices. In the base of environmental protection, the toxicity of lead also demands for long working life for perovskite devices to avoid the disposal of lead waste. [27][28][29] These problems indicate that mechanical stability remains as a significant concern for flexible perovskite devices. Solutions including interface treatment and mixture of polymer have been employed, but they can only withstand limited bending cycles and strength. [30][31][32][33][34] To resolve these critical issues, the concept of self-healing has also been applied to flexible perovskite devices. [35,36] Selfhealing polymers can act as encapsulation layers or flexible substrates, which only prevent external air moisture while cracks inside perovskite films still exist and block carrier transport. In addition, it is difficult to endow the ABX 3 crystal structure of perovskite with special chemical bonds (such as H-bonds) to trigger the capability of self-healing. To address this challenge, Chen et al. creatively utilized polyurethanes (PU) to provide a micro-self-healing framework for perovskite crystals without damaging its power conversion efficiency and cracks caused by stretching were healed by heating films at 100 °C. [36] The heating treatment may damage organic carrier transport layers or accelerate ion diffusion of metal electrodes; moreover, perovskite devices usually operate at the room temperature. Thus, it is necessary to design a perovskite material with self-healing capability which does not need any harsh external stimuli.Herein, we design a moisture-triggered self-healing flexible perovskite photodetector with poly(vinyl alcohol) (PVA) as an additive. Moisture, as a negative factor affecting the stability of perovskite, is also used to activate the self-healing process of perovskite films. PVA organic framework fills grain boundaries, which are weak points that generate cracks. The moisturesensitive framework absorbs water molecules from the air and recovers the conductivity lost from the cracks, which is proved to be the dominant reason for the decomposition of the flexible lateral perovskite photodetector. The device can recover over 90% of its initial performance under a relative humidity (RH) of 80%, maintaining remarkable mechanical stability. Furthermore, PVA stabilizes the formamidinium lead iodide (FAPbI 3 ) film in the black phase, and the photodetector shows a high responsivity Flexible devices are urgently required to meet the demands of next-generation optoelectronic devices and metal halide perovskites are proven to be suitable materials for realizing flexible photovoltaic devices. However, the tolerance to moisture corrosion and repeated mechanical bending remains a critical c...

Chirality‐Dependent Second‐Order Nonlinear Optical Effect in 1D Organic–Inorganic Hybrid Perovskite Bulk Single Crystal

“…As an ew kind of multifunction materials,o rganicinorganic hybrid perovskites (OIHPs) with chemical designability,s tructural diversity,l ow-cost and low-temperature solution-processability have been widely concerned in many fields, [1,2] such as solar cells, [3,4] nonlinear optics (NLO), [5,6] ferroelectrics, [7,8] light emitting diodes [9,10] and photodetectors. [11][12][13] Meanwhile,OIHPs not only have the obvious grains and grain boundaries like ceramics,b ut also possess the rotation of organic ions like polymer.A mong these,c hiral OIHPs with asymmetric centers have exceptional attractive properties,s uch as circular dichroism, [14,15] chiroptoelectronics, [16] optical rotation, [16] second-harmonic generation (SHG), [5] and ferroelectricity, [17,18] which have attracted more and more attentions in many fields.The influence of chirality on the properties of OIHPs is mainly focused on the chiralitydependent circular photogalvanic effect, [19,20] spin transport, [21] optical selection rules [22] and chirality-induced ferroelectrics. [23] Due to the inherent noncentrosymmetry of chiral OIHPs,which endowing the chiral OIHPs produce asecondorder doubling frequency response by NLO effects.F urthermore,anideal NLO crystal must satisfy two conditions,one is non-centrosymmetric and the other one is phase matching (PM).…”

Interface Chelation Induced by Pyridine‐Based Polymer for Efficient and Durable Air‐Processed Perovskite Solar Cells

“…Moreover, the obvious shifts of Pb 4f 7/2 and 4f 5/2 peaks also verified the strong interaction between SHP and Pb 2+ [4b] . Besides, as a consequence of the incorporation of SHP additive, the binding energy of I 3d 3/2 and 3d 5/2 became smaller than that without SHP, indicating a high electronegativity in Figure 3 d [11c] . Therefore, attributing to these synergistic interactions of SHP, enhanced crystallinity with oriented growth were achieved [18]…”

“…In comparison with the pristine precursor solution, SHP provided the crystallographic templates and increased the critical concentration ( C c , representing the difficulty of nucleation), contributing to the passivation defects and enlarged crystal grains. Besides, SHP can passivate iodine (I − ) vacancy to compensate for the electronic loss at the grain boundary, thus prevents the electrons from being captured by the defects and reduces recombination [11c, 15] …”

Thermal‐Triggered Dynamic Disulfide Bond Self‐Heals Inorganic Perovskite Solar Cells

“…Top‐view SEM images in Figure 1d, e demonstrate an enlarged grain size for the perovskite film after adding 0.10 mg mL −1 PU without changing the crystal phase (XRD patterns of perovskite films in Figure S3) and film thickness (cross‐sectional SEM images in Figure S4), but large dosage (such as 0.50 mg mL −1 PU) has a negative effect on the morphology (Figure S5) and optical absorbance (Figure S6). Considering that uniformly distributed PU can function as a three‐dimensional skeleton to support the perovskite growth, the intrinsic mechanism for improved film quality is mainly attributed to the interaction between PU and PbI 2 or PbBr 2 , such as the formation of hydrogen bonds (−N−H⋅⋅⋅X−Pb−X), [26, 27] to slow down the crystallization speed. By combining the increased photoluminescence (PL) intensity and prolonged carrier lifetime obtained from the time‐resolved PL (TRPL) spectra in Figure S7, it is concluded that the nonradiative recombination induced by detrimental defects in the perovskite film is significantly suppressed for maximizing the photovoltaic performances [28]…”