Hybrid organic–inorganic perovskites have attracted intensive interest as light absorbing materials in solid‐state solar cells. Herein, we demonstrate a high‐performance CH3NH3PbI3‐based perovskite photodetector constructed on the flexible indium tin oxide (ITO) coated substrate even after 200 bending cycles. The as‐fabricated devices show high responsivity, broad spectrum response from ultraviolet to whole visible light, long‐term stability, and high on‐off ratio. Particularly, atomic layer deposition technique was used to deposit the ultrathin Al2O3 film on devices, functioning as a protection layer to effectively enhance the stability and durability of perovskite photodetectors. The first all‐perovskite self‐powered nanosystem was successfully assembled by integrating a perovskite solar cell with a perovskite photodetector. Driven by the perovskite solar cell, the photodetector exhibits fast and stable response to illuminated light at a low working voltage less than 1.0 V. This stable integrated nanosystem has promising applications in which photodetectors can work in harsh environments without external power sources.

Self-powered flexible photodetectors without an external power source can meet the demands of next-generation portable and wearable nanodevices; however, the performance is far from satisfactory becuase of the limited match of flexible substrates and light-sensitive materials with proper energy levels. Herein, a novel self-powered flexible fiber-shaped photodetector based on double-twisted perovskite-TiO -carbon fiber and CuO-Cu O-Cu wire is designed and fabricated. The device shows an ultrahigh detectivity of 2.15 × 10 Jones under the illumination of 800 nm light at zero bias. CuO-Cu O electron block bilayer extends response range of perovskite from 850 to 1050 nm and suppresses dark current down to 10 A. The fast response speed of less than 200 ms is nearly invariable after dozens of cycles of bending at the extremely 90 bending angle, demonstrating excellent flexibility and bending stability. These parameters are comparable and even better than reported flexible and even rigid photodetectors. The present results suggest a promising strategy to design photodetectors with integrated function of self-power, flexibility, and broadband response.

possess lower dark currents and higher detectivities. In spite of great progresses, it is complicated to fabricate composite electronic transport layers (ETLs) with matched crystal lattices and energy levels, otherwise the newly formed interface in the composite may bring about large amounts of defects which act as trap sites and recombination centers.Spatially graded composition (bandgap) is an effective route to continuously tune energy levels and bandgap in semiconductors, [20,21] in which the interfacial recombination is alleviated or removed and a graded built-in potential through the whole bulk is produced, enabling stronger separation capability of photogenerated electron-hole pairs. This concept provides a new platform for designing high-performance optoelectronic devices. For example, Krol and co-workers fabricated the gradient W-doped BiVO 4 as a photoanode of photoelectrochemical cell. [22] Compared to the homogeneously doped BiVO 4 , the continuous built-in band bending induces the directional transfer of photogenerated holes from core to surface and thus increases the carrier separation efficiency to 60%. Tailoring the gradient bandgap from 0.35 to 1.42 eV, Pan and co-workers synthesized InAs x P 1-x nanosheets for band-selective infrared photodetectors. [23] We reported graded CdS x Se 1-x nanobelt solar cells by utilizing continuous stepped energy levels to drive electrons and holes toward opposite direction. [24] In p-i-n structured devices, [25][26][27][28] graded composition (bandgap) is basically used in the main photosensitive layer, for which the narrow bandgap region increases the absorption wavelength range, the large bandgap results in a high voltage output, and graded bandgap structure promotes the carriers transport. Inspired by previous results, with the introduction of gradient built-in band bending at the charge extraction layer/perovskite interface, the energy band offset is expected to provide the driving force for enhanced carrier separation, suppressed electron reflux, and reduced recombination, boosting the performance of perovskite photodetectors.In this work, we present a high-performance self-powered photodetector by integrating perovskite with gradient O-doped CdS nanorod array. For the first time, the continuous builtin band bending is introduced at the charge extraction layer/ perovskite interface to manipulate the transfer behavior of carriers in perovskite photodetectors. The optoelectronic measurements reveal that both the responsivity and the response speed of devices strongly depend on the structure of energy band bending. The optimum gradient O-doped CdS/perovskite Self-powered photodetectors are highly desired to meet the great demand in applications of sensing, communication, and imaging. Manipulating the carrier separation and recombination is critical to achieve high performance. In this paper, a self-powered photodetector based on the integrated gradient O-doped CdS nanorod array and perovskite is presented. Through optimizing the degree of continuous built-in ba...

In a photoelectrochemical (PEC) cell for water splitting, the critical issue is charge separation and transport, which is usually completed by designing semiconductor heterojunctions. TiO2 anatase-rutile mixed junctions could largely improve photocatalytic properties, but impairs PEC water splitting performance. We designed and prepared two types of TiO2 heterostructures with the anatase thin film and rutile nanowire phases organized in different sequences. The two types of heterostructures were used as PEC photoanodes for water splitting and demonstrated completely opposite results. Rutile nanowires on anatase film demonstrated enhanced photocurrent density and onset potential, whereas strong negative performance was obtained from anatase film on rutile nanowire structures. The mechanism was investigated by photoresponse, light absorption and reflectance, and electrochemical impedance spectra. This work revealed the significant role of phase sequence in performance gain of anatase-rutile TiO2 heterostructured PEC photoanodes.

Metal halide perovskite solar cells (PSCs), with their exceptional properties, show promise as photoelectric converters. However, defects in the perovskite layer, particularly at the grain boundaries (GBs), seriously restrict the performance and stability of PSCs. Now, a simple post‐treatment procedure involves applying 2‐aminoterephthalic acid to the perovskite to produce efficient and stable PSCs. By optimizing the post‐treatment conditions, we created a device that achieved a remarkable power conversion efficiency (PCE) of 21.09 % and demonstrated improved stability. This improvement was attributed to the fact that the 2‐aminoterephthalic acid acted as a cross‐linking agent that inhibited the migration of ions and passivated the trap states at GBs. These findings provide a potential strategy for designing efficient and stable PSCs regarding the aspects of defect passivation and crystal growth.