Mixed‐Dimensional 1D ZnO–2D WSe2 van der Waals Heterojunction Device for Photosensors

2D layered van der Waals (vdW) atomic crystals are an emerging class of new materials that are receiving increasing attention owing to their unique properties. In particular, the dangling‐bond‐free surface of 2D materials enables integration of differently dimensioned materials into mixed‐dimensional vdW heterostructures. Such mixed‐dimensional heterostructures herald new opportunities for conducting fundamental nanoscience studies and developing nanoscale electronic/optoelectronic applications. This study presents a 1D ZnO nanowire (n‐type)–2D WSe₂ nanosheet (p‐type) vdW heterojunction diode for photodetection and imaging process. After amorphous fluoropolymer passivation, the ZnO–WSe₂ diode shows superior performance with a much‐enhanced rectification (ON/OFF) ratio of over 10⁶ and an ideality factor of 3.4–3.6 due to the carbon–fluorine (C? F) dipole effect. This heterojunction device exhibits spectral photoresponses from ultraviolet (400 nm) to near infrared (950 nm). Furthermore, a prototype visible imager is demonstrated using the ZnO–WSe₂ heterojunction diode as an imaging pixel. To the best of our knowledge, this is the first demonstration of an optoelectronic device based on a 1D–2D hybrid vdW heterojunction. This approach using a 1D ZnO–2D WSe₂ heterojunction paves the way for the further development of electronic/optoelectronic applications using mixed‐dimensional vdW heterostructures.     

High‐Sensitivity Floating‐Gate Phototransistors Based on WS2 and MoS2

In recent years, 2D layered materials have been considered as promising photon absorption channel media for next‐generation phototransistors due to their atomic thickness, easily tailored single‐crystal van der Waals heterostructures, ultrafast optoelectronic characteristics, and broadband photon absorption. However, the photosensitivity obtained from such devices, even under a large bias voltage, is still unsatisfactory until now. In this paper, high‐sensitivity phototransistors based on WS₂ and MoS₂ are proposed, designed, and fabricated with gold nanoparticles (AuNPs) embedded in the gate dielectric. These AuNPs, located between the tunneling and blocking dielectric, are found to enable efficient electron trapping in order to strongly suppress dark current. Ultralow dark current (10^?11 A), high photoresponsivity (1090 A W^?1), and high detectivity (3.5 × 10¹¹ Jones) are obtained for the WS₂ devices under a low source/drain and a zero gate voltage at a wavelength of 520 nm. These results demonstrate that the floating‐gate memory structure is an effective configuration to achieve high‐performance 2D electronic/optoelectronic devices.     

Enhancing Resistive Switching Performance and Ambient Stability of Hybrid Perovskite Single Crystals via Embedding Colloidal Quantum Dots

Hybrid organic‐inorganic halide perovskites are actively pursued for optoelectronic technologies, but the poor stability is the Achilles’ heel of these materials that hinders their applications. Very recently, it has been shown that lead sulfide (PbS) quantum dots (QDs) can form epitaxial interfaces with the perovskite matrix and enhance the overall stability. In this work, it is demonstrated that embedding QDs can significantly modify the transport property of pristine perovskite single crystals, endowing them with new functionalities besides being structurally robust and free from grain boundaries. Resistive switching memory devices are constructed using solution‐processed CH₃NH₃PbBr₃ (MAPbBr₃) perovskite single crystals and the QD‐embedded counterparts. It is found that QDs could significantly enhance the charge transport and reduce the current–voltage hysteresis. The pristine singe crystal device exhibits negative differential resistance, while the QD‐embedded crystals are featured with filament‐type switching behavior and much improved device stability. This study underscores the potential of QD‐embedded hybrid perovskites as a new media for advanced electronic devices.     

Sensitive and Ultrabroadband Phototransistor Based on Two‐Dimensional Bi2O2Se Nanosheets

Bi₂O₂Se, a high‐mobility and air‐stable 2D material, has attracted substantial attention for application in integrated logic electronics and optoelectronics. However, achieving an overall high performance over a wide spectral range for Bi₂O₂Se‐based devices remains a challenge. A broadband phototransistor with high photoresponsivity (R) is reported that comprises high‐quality large‐area ( ≈ 180 µm) Bi₂O₂Se nanosheets synthesized via a modified chemical vapor deposition method with a face‐down configuration. The device covers the ultraviolet (UV), visible (Vis), and near‐infrared (NIR) wavelength ranges (360–1800 nm) at room temperature, exhibiting a maximum R of 108 696 A W^?1 at 360 nm. Upon illumination at 405 nm, the external quantum efficiency, R, and detectivity (D*) of the device reach up to 1.5 × 10⁷%, 50055 A W^?1, and 8.2 × 10¹² Jones, respectively, which is attributable to a combination of the photogating, photovoltaic, and photothermal effects. The devices reach a ?3 dB bandwidth of 5.4 kHz, accounting for a fast rise time (τ_rise) of 32 µs. The high sensitivity, fast response time, and environmental stability achieved simultaneously in these 2D Bi₂O₂Se phototransistors are promising for high‐quality UV and IR imaging applications.     

Perovskite‐Based Phototransistors and Hybrid Photodetectors

In the past several years, organic–inorganic hybrid perovskites and all inorganic perovskites have attracted enormous research interest in a variety of optoelectronic applications including solar cells, light‐emitting diodes, semiconductor lasers, and photodetectors for their plenty of appealing electrical and optoelectrical properties. Benefiting from the inherent amplification function of transistors and the pronounced photogating effect, perovskite‐based phototransistors and hybrid photodetectors can provide very high photoresponsivity and gain, rendering them highly promising for some specific applications especially ultrasensitive light detection. A review on the recent progress of phototransistors and hybrid photodetectors using perovskites as light‐sensitive materials is presented. The efforts and development in 3D and 2D perovskite‐based phototransistors, and perovskite/functional material (e.g., graphene, 2D semiconductors, organic semiconductors, and other semiconductors) heterojunction‐based hybrid photodetectors are introduced and discussed systematically. Some processing techniques for optimizing device performance are also addressed. In the final section, a conclusion of the research achievements is presented and possible challenges as well as outlook are provided to guide future activity in this research field.     

Interfacial Charge Behavior Modulation in Perovskite Quantum Dot‐Monolayer MoS2 0D‐2D Mixed‐Dimensional van der Waals Heterostructures

Fundamental understanding of charge behavior inside heterostructures is of vital importance for advancing high‐performance optoelectronic applications. However, the charge behavior of 0D‐2D mixed‐dimensional van der Waals heterostructures (MvdWHs) in the photoexcited state remains elusive. In this work, an energy band alignment protocol is adopted to realize effective energy band structure engineering inside 0D‐2D MvdWHs of perovskite quantum dots and MoS₂ monolayer with precisely designed typical type I and type II heterostructures, respectively. A profile and in‐depth understanding of interfacial photoinduced charge behavior is determined from two opposite perspectives based on MvdWHs. Sufficient comparison of a series of optical characterization results, including Raman shift, quenched photoluminescence, visualized suppressed fluorescence intensity, and shortened fluorescence lifetime imaging, clearly verifies that interfacial charge behavior can be tailored by varying the band alignment in 0D‐2D MvdWHs. Furthermore, the photoresponse performance and the relatively stronger and weaker photogating effects of such MvdWH‐based phototransistors also demonstrate modulation of interfacial charge behavior in 0D‐2D MvdWHs via energy band structure engineering, which is still feasible for optoelectronic performance optimization. These results are expected to shed light on designing novel functional devices and advancing the development process of 0D‐2D MvdWHs in the foreseeable future.     

Novel and Enhanced Optoelectronic Performances of Multilayer MoS2–WS2 Heterostructure Transistors

Van der Waals heterostructures designed by assembling isolated two‐dimensional (2D) crystals have emerged as a new class of artificial materials with interesting and unusual physical properties. Here, the multilayer MoS₂–WS₂ heterostructures with different configurations are reported and their optoelectronic properties are studied. It is shown that the new heterostructured material possesses new functionalities and superior electrical and optoelectronic properties that far exceed the one for their constituents, MoS₂ or WS₂. The vertical transistor exhibits a novel rectifying and bipolar behavior, and can also act as photovoltaic cell and self‐driven photodetector with photo‐switching ratio exceeding 10³. The planar device also exhibits high field‐effect ON/OFF ratio (>10⁵), high electron mobility of 65 cm²/Vs, and high photo­responsivity of 1.42 A/W compared to that in isolated multilayer MoS₂ or WS₂ nanoflake transistors. The results suggest that formation of MoS₂–WS₂ heterostructures could significantly enhance the performance of optoelectronic devices, thus open up possibilities for future nanoelectronic, photovoltaic, and optoelectronic applications.     

High‐Performance Transition Metal Dichalcogenide Photodetectors Enhanced by Self‐Assembled Monolayer Doping

Most doping research into transition metal dichalcogenides (TMDs) has been mainly focused on the improvement of electronic device performance. Here, the effect of self‐assembled monolayer (SAM)‐based doping on the performance of WSe₂‐ and MoS₂‐based transistors and photodetectors is investigated. The achieved doping concentrations are ≈1.4 × 10¹¹ for octadecyltrichlorosilane (OTS) p‐doping and ≈10¹¹ for aminopropyltriethoxysilane (APTES) n‐doping (nondegenerate). Using this SAM doping technique, the field‐effect mobility is increased from 32.58 to 168.9 cm² V^?1 s in OTS/WSe₂ transistors and from 28.75 to 142.2 cm² V^?1 s in APTES/MoS₂ transistors. For the photodetectors, the responsivity is improved by a factor of ≈28.2 (from 517.2 to 1.45 × 10⁴ A W^?1) in the OTS/WSe₂ devices and by a factor of ≈26.4 (from 219 to 5.75 × 10³ A W^?1) in the APTES/MoS₂ devices. The enhanced photoresponsivity values are much higher than that of the previously reported TMD photodetectors. The detectivity enhancement is ≈26.6‐fold in the OTS/WSe₂ devices and ≈24.5‐fold in the APTES/MoS₂ devices and is caused by the increased photocurrent and maintained dark current after doping. The optoelectronic performance is also investigated with different optical powers and the air‐exposure times. This doping study performed on TMD devices will play a significant role for optimizing the performance of future TMD‐based electronic/optoelectronic applications.     

Few‐Layered PtS2 Phototransistor on h‐BN with High Gain

The very recently rediscovered group‐10 transition metal dichalcogenides (TMDs) such as PtS₂ and PtSe₂, have joined the 2D material family as potentially promising candidates for electronic and optoeletronic applications due to their theoretically high carrier mobility, widely tunable bandgap, and ultrastability. Here, the first exploration of optoelectronic application based on few‐layered PtS₂ using h‐BN as substrate is presented. The phototransistor exhibits high responsivity up to 1.56 × 10³ A W^?1 and detectivity of 2.9 × 10¹¹ Jones. Additionally, an ultrahigh photogain ≈2 × 10⁶ is obtained at a gate voltage V _g = 30 V, one of the highest gain among 2D photodetectors, which is attributed to the existence of trap states. More interestingly, the few‐layered PtS₂ phototransistor shows a back gate modulated photocurrent generation mechanism, that is, from the photoconductive effect dominant to photogating effect dominant via tuning the gate voltage from the OFF state to the ON state. Such good properties combined with gate‐controlled photoresponse of PtS₂ make it a competitive candidate for future 2D optoelectronic applications.     

Hybrid Perovskite Quantum Dot/Non-Fullerene Molecule Solar Cells with Efficiency Over 15%

Organic-inorganic hybrid film using conjugated materials and quantum dots (QDs) are of great interest for solution-processed optoelectronic devices, including photovoltaics (PVs). However, it is still challenging to fabricate conductive hybrid films to maximize their PV performance. Herein, for the first time, superior PV performance of hybrid solar cells consisting of CsPbI₃ perovskite QDs and Y6 series non-fullerene molecules is demonstrated and further highlights their importance on hybrid device design. In specific, a hybrid active layer is developed using CsPbI₃ QDs and non-fullerene molecules, enabling a type-II energy alignment for efficient charge transfer and extraction. Additionally, the non-fullerene molecules can well passivate the QDs, reducing surface defects and energetic disorder. The champion CsPbI₃ QD/Y6-F hybrid device has a record-high efficiency of 15.05% for QD/organic hybrid PV devices, paving a new way to construct solution-processable hybrid film for efficient optoelectronic devices.     

Core/Shell PbSe/PbS QDs TiO2 Heterojunction Solar Cell

Quasi type‐II PbSe/PbS quantum dots (QDs) are employed in a solid state high efficiency QD/TiO₂ heterojunction solar cell. The QDs are deposited using layer‐by‐layer deposition on a half‐micrometer‐thick anatase TiO₂ nanosheet film with (001) exposed facets. Theoretical calculations show that the carriers in PbSe/PbS quasi type‐II QDs are delocalized over the entire core/shell structure, which results in better QD film conductivity compared to PbSe QDs. Moreover, PbS shell permits better stability and facile electron injection from the QDs to the TiO₂ nanosheets. To complete the electrical circuit of the solar cell, a Au film is evaporated as a back contact on top of the QDs. This PbSe/PbS QD/TiO₂ heterojunction solar cell produces a light to electric power conversion efficiency (η) of 4% with short circuit photocurrent (J_sc) of 17.3 mA/cm². This report demonstrates highly efficient core/shell near infrared QDs in a QD/TiO₂ heterojunction solar cell.     

Optoelectronics based on 2D TMDs and heterostructures

2D materials including graphene and TMDs have proven interesting physical properties and promising optoelectronic applications. We reviewed the growth, characterization and optoelectronics based on 2D TMDs and their heterostructures, and demonstrated their unique and high quality of performances. For example, we observed the large mobility, fast response and high photo-responsivity in MoS₂, WS₂ and WSe₂ phototransistors, as well as the novel performances in vdW heterostructures such as the strong interlayer coupling, am-bipolar and rectifying behaviour, and the obvious photovoltaic effect. It is being possible that 2D family materials could play an increasingly important role in the future nano- and opto-electronics, more even than traditional semiconductors such as silicon.     

Controlled Fabrication of PbS Quantum‐Dot/Carbon‐Nanotube Nanoarchitecture and its Significant Contribution to Near‐Infrared Photon‐to‐Current Conversion

A solution‐processed nanoarchitecture based on PbS quantum dots (QDs) and multi‐walled carbon nanotubes (MWCNTs) is synthesized by simply mixing the pre‐synthesized high‐quality PbS QDs and oleylamine (OLA) pre‐functionalized MWCNTs. Pre‐functionalization of MWCNTs with OLA is crucial for the attachment of PbS QDs and the coverage of QDs on the surface of MWCNTs can be tuned by varying the ratio of PbS QDs to MWCNTs. The apparent photoluminescence (steady‐state emission and fluorescence lifetime) “quenching” effect indicates efficient charge transfer from photo‐excited PbS QDs to MWCNTs. The as‐synthesized PbS‐QD/MWCNT nanoarchitecture is further incorporated into a hole‐conducting polymer poly(3‐hexylthiophene)‐(P3HT), forming the P3HT:PbS‐QD/MWCNT nanohybrid, in which the PbS QDs act as a light harvester for absorbing irradiation over a wide wavelength range of the solar spectrum up to near infrared (NIR, ≈1430 nm) range; whereas, the one‐dimensional MWCNTs and P3HT are used to collect and transport photoexcited electrons and holes to the cathode and anode, respectively. Even without performing the often required “ligand exchange” to remove the long‐chained OLA ligands, the built nanohybrid photovoltaic (PV) device exhibits a largely enhanced power conversion efficiency (PCE) of 3.03% as compared to 2.57% for the standard bulk hetero‐junction PV cell made with P3HT and [6,6]‐Phenyl‐C₆₁‐Butyric Acid Methyl Ester (PCBM) mixtures. The improved performance of P3HT:PbS‐QD/MWCNT nanohybrid PV device is attributed to the significantly extended absorption up to NIR by PbS QDs as well as the effectively enhanced charge separation and transportation due to the integrated MWCNTs and P3HT. Our research results suggest that properly integrating QDs, MWCNTs, and polymers into nanohybrid structures is a promising approach for the development of highly efficient PV devices.     

Fully Transparent p‐MoTe2 2D Transistors Using Ultrathin MoOx/Pt Contact Media for Indium‐Tin‐Oxide Source/Drain

Since transition metal dichalcogenide (TMD) semiconductors are found as 2D van der Waals materials with a discrete energy bandgap, many 2D‐like thin field effect transistors (FETs) and PN diodes are reported as prototype electrical and optoelectronic devices. As a potential application of display electronics, transparent 2D FET devices are also reported recently. Such transparent 2D FETs are very few in report, yet no p‐type channel 2D‐like FETs are seen. Here, 2D‐like thin transparent p‐channel MoTe₂ FETs with oxygen (O₂) plasma‐induced MoO_x/Pt/indium‐tin‐oxide (ITO) contact are reported for the first time. For source/drain contact, 60 s short O₂ plasma and ultrathin Pt‐deposition processes on MoTe₂ surface are sequentially introduced before ITO thin film deposition and patterning. As a result, almost transparent 2D FETs are obtained with a decent mobility of ≈5 cm² V^?1 s^?1, a high ON/OFF current ratio of ≈10⁵, and 70% transmittance. In particular, for normal MoTe₂ FETs without ITO, O₂ plasma process greatly improves the hole injection efficiency and device mobility (≈60 cm² V^?1 s^?1), introducing ultrathin MoO_x between Pt source/drain and MoTe₂. As a final device application, a photovoltaic current modulator, where the transparent FET stably operates as gated by photovoltaic effects, is integrated.     

Capillary‐Bridge Mediated Assembly of Conjugated Polymer Arrays toward Organic Photodetectors

Large‐scale patterning of high‐quality organic semiconductors is crucial for the fabrication of optoelectronic devices with high efficiency and low cost. Yet, owing to the uncontrollable dewetting dynamics of organic liquid in conventional solution patterning techniques, large defect density of organic architectures is inevitable, which is detrimental to the device performance. To address this challenge, herein a capillary‐bridge‐mediated assembly technique is developed for regulating the dewetting process, yielding large‐scale 1D microstructure ordered arrays. The 1D arrays organic photodetectors exhibit a high optoelectronic performance of light on/off ratio exceeding 100, responsivity of 3.24 A W^?1, detectivity of 3.20 × 10¹¹ Jones and fast response speed, showing a great improvement compared with spin‐coated membrane devices. In addition, the significant enhancement of the device photodetection under the electronic field modulation is investigated by applying a back‐gate voltage and explained with the photocurrent predominating in the OFF state and the neglected thermocurrent and tunneling current promoting in the ON state of the phototransistor devices. The research offers a new insight for the facile fabrication of large‐scale integrated photodetectors and other organic devices based on patterned conjugated polymers.     

Facile Assembly of High‐Quality Organic–Inorganic Hybrid Perovskite Quantum Dot Thin Films for Bright Light‐Emitting Diodes

Organic‐inorganic hybrid perovskite (CH₃NH₃PbX₃, X = Cl, Br or I) quantum dots (QDs) have shown superior optoelectronic properties and have been regarded as a most ideal material for next‐generation optoelectronic devices, particularly for QDs‐based light‐emitting diodes (QLEDs). However, there are only a few reports on CH₃NH₃PbX₃ QLEDs and the reported performance is still very poor, primarily due to the difficulties in the fabrication of high‐quality compact QDs thin films. In this work, an electric‐field‐assisted strategy is developed for efficient fabrication of uniform CH₃NH₃PbBr₃ QDs thin films with high photoluminescence quantum yields (PLQY, 80%–90%) from dilute CH₃NH₃PbBr₃ QDs suspensions (≈0.1 mg mL^‐1) within 5 mins. Benefited from the high‐quality CH₃NH₃PbBr₃ QDs thin films, the corresponding QLEDs deliver a highly bright green emission with maximum luminances of 12450 cd m². Furthermore, a current efficiency of 12.7 cd A^‐1, a power efficiency of 9.7 lm W^‐1, and an external quantum efficiency (EQE) of 3.2% were acheived by enhancing the hole injection. This performance represents the best results for CH₃NH₃PbBr₃ QDs‐based QLEDs reported to date. These results indicate an important progress in the fabrication of high‐performance CH₃NH₃PbX₃ QLEDs and demonstrate their huge potential for next‐generation displays and lighting.     

Ultra‐Thin Layered Ternary Single Crystals [Sn(SxSe1−x)2] with Bandgap Engineering for High Performance Phototransistors on Versatile Substrates

2D ternary semiconductor single crystals, an emerging class of new materials, have attracted significant interest recently owing to their great potential for academic interest and practical application. In addition to other types of metal dichalcogenides, 2D tin dichalcogenides are also important layered compounds with similar capabilities. Yet, multi‐elemental single crystals enable to assist multiple degrees of freedom for dominant physical properties via ratio alteration. This study reports the growth of single crystals Se‐doped SnS₂ or SnSSe alloys, and demonstrates their capability for the fabrication of phototransistors with high performance. Based on exfoliation from bulk high quality single crystals, this study establishes the characteristics of few‐layered SnSSe in structural, optical, and electrical properties. Moreover, few‐layered SnSSe phototransistors are fabricated on both rigid (SiO₂/Si) and versatile polyethylene terephthalate substrates and their optoelectronic properties are examined. SnSSe as a phototransistor is demonstrated to exhibit a high photoresponsivity of about 6000 A W^?1 with ultra‐high photogain ≈8.8 × 10⁵, fast response time ≈9 ms, and specific detectivity (D*) ≈8.2 × 10¹² J. These unique features are much higher than those of recently published phototransistors configured with other few‐layered 2D single crystals, making ultrathin SnSSe a highly qualified candidate for next‐generation optoelectronic applications.     

High Responsivity Phototransistors Based on Few‐Layer ReS2 for Weak Signal Detection

2D transition metal dichalcogenides are emerging with tremendous potential in many optoelectronic applications due to their strong light–matter interactions. To fully explore their potential in photoconductive detectors, high responsivity is required. Here, high responsivity phototransistors based on few‐layer rhenium disulfide (ReS₂) are presented. Depending on the back gate voltage, source drain bias and incident optical light intensity, the maximum attainable photoresponsivity can reach as high as 88 600 A W^?1, which is a record value compared to other individual 2D materials with similar device structures and two orders of magnitude higher than that of monolayer MoS₂. Such high photoresponsivity is attributed to the increased light absorption as well as the gain enhancement due to the existence of trap states in the few‐layer ReS₂ flakes. It further enables the detection of weak signals, as successfully demonstrated with weak light sources including a lighter and limited fluorescent lighting. Our studies underscore ReS₂ as a promising material for future sensitive optoelectronic applications.     

Self‐Aligned and Scalable Growth of Monolayer WSe2–MoS2 Lateral Heterojunctions

2D layered heterostructures have attracted intensive interests due to their unique optical, transport, and interfacial properties. The laterally stitched heterojunction based on dissimilar 2D transition metal dichalcogenides forms an intrinsic p–n junction without the necessity of applying an external voltage. However, no scalable processes are reported to construct the devices with such lateral heterostructures. Here, a scalable strategy, two‐step and location‐selective chemical vapor deposition, is reported to synthesize self‐aligned WSe₂–MoS₂ monolayer lateral heterojunction arrays and demonstrates their light‐emitting devices. The proposed fabrication process enables the growth of high‐quality interfaces and the first successful observation of electroluminescence at the WSe₂–MoS₂ lateral heterojunction. The electroluminescence study has confirmed the type‐I alignment at the interface rather than commonly believed type‐II alignment. This self‐aligned growth process paves the way for constructing various 2D lateral heterostructures in a scalable manner, practically important for integrated 2D circuit applications.     

Pulsed Laser Ablation Based Synthesis of PbS‐Quantum Dots‐Decorated One‐Dimensional Nanostructures and Their Direct Integration into Highly Efficient Nanohybrid Heterojunction‐Based Solar Cells

The pulsed laser deposition (PLD) technique is used for the direct fabrication of nanohybrid heterojunctions (NH‐HJs) solar cells exhibiting high PCE and excellent stability in air without any encapsulation and/or resorting to any surface treatment, ligand engineering and/or post‐synthesis processing. The NH‐HJs are achieved through the PLD‐based decoration of hydrothermally‐grown one‐dimensional TiO₂ nanorods (TiO₂‐NRs) by PbS quantum dots (PbS‐QDs). By optimizing both the amount of PbS‐QDs (via the number of laser ablation pulses) and the length of the TiO₂‐NRs, it is possible to achieve optimal NH‐HJs based PV devices with high power conversion efficiency (PCE) of 4.85%. This high PCE is found to occur for an optimal length of the NRs (≈290 nm) which coincides with the average penetration depth of PbS‐QDs into the porous TiO₂‐NRs matrix, leading thereby to the formation of the largest extent of NH‐HJs. Most importantly, the PCE of these novel devices is found to be fairly stable for several months under ambient air. The addition of single‐wall carbon nanotubes (SWCNTs) onto the TiO₂‐NRs prior to their decoration by PbS‐QDs is shown to further enhance their PCE to a value as high as 5.3%, because of additional light absorption and improved charge collection ensured by SWCNTs.