Interface Engineering To Boost Photoresponse Performance of Self-Powered, Broad-Bandwidth PEDOT:PSS/Si Heterojunction Photodetector

Boosting the UV-vis-NIR Photodetection Performance of MoS2 through the Cavity Enhancement Effect and Bulk Heterojunction Strategy

Navigating more effective methods to enhance the photon utilization of photodetectors poses a significant challenge. This study initially investigates the impact of morphological alterations in 2H-MoS2 on photodetector (PD) performance. The results reveal that compared to layered MoS2 (MoS2 NLs), MoS2 nanotubes (MoS2 NTs) impart a cavity enhancement effect through multiple light reflections. This structural feature significantly enhances the photodetection performance of the MoS2-based PDs. We further employ the heterojunction strategy to construct Y-TiOPc NPs:MoS2 NTs, utilizing Y-TiOPc NPs (Y-type titanylphthalocyanine) as the vis-NIR photosensitizer and MoS2 NTs as the photon absorption enhancer. This approach not only addresses the weak absorption of MoS2 NTs in the near-infrared region but also enhances carrier generation, separation, and transport efficiency. Additionally, the band bending phenomenon induced by trapped-electrons at the interface between ITO and the photoactive layer significantly enhances the hole tunneling injection capability from the external circuit. By leveraging the synergistic effects of the aforementioned strategies, the PD based on Y-TiOPc NPs:MoS2 NTs (Y:MT-PD) exhibits superior photodetection performance in the wavelength range of 365-940 nm compared to MoS2 NLs-based PD and MoS2 NTs-based PD. Particularly noteworthy are the peak values of key metrics for Y:MT-PD, such as EQE, R, and D* that are 4947.6%, 20588 mA/W, and 1.94 × 1012 Jones, respectively. The multiperiod time-resolved photocurrent response curves of Y:MT-PD also surpass those of the other two PDs, displaying rapid, stable, and reproducible responses across all wavelengths. This study provides valuable insights for the further development of photoactive materials with a high photon utilization efficiency.

Modulating the density of silicon nanowire arrays for high-performance hydrovoltaic devices

Hydrovoltaic devices (HDs) based on silicon nanowire (SiNW) arrays have received intensive attention due to their simple preparation, mature processing technology, and high output power. Investigating the impact of structure parameters of SiNWs on the performance of HDs can guide the optimization of the devices, but related research is still not sufficient. This work studies the effect of the SiNW density on the performance of HDs. SiNW arrays with different densities were prepared by controlling the react time of Si wafers in the seed solution (tseed) in metal-assisted chemical etching. Density of SiNW array gradually decreases with the increase oftseed. HDs were fabricated based on SiNW arrays with different densities. The research results indicate that the open-circuit voltage gradually decreases with increasingtseed, while the short-circuit current first increases and then decreases with increasingtseed. Overall, SiNW devices withtseedof 20 s and 60 s have the best output performance. The difference in output performance of HDs based on SiNWs with different densities is attributed to the difference in the gap sizes between SiNWs, specific surface area of SiNWs, and the number of SiNWs in parallel. This work gives the corresponding relationship between the preparation conditions of SiNWs, array density, and output performance of hydrovoltaic devices. Density parameters of SiNW arrays with optimized output performance and corresponding preparation conditions are revealed. The relevant results have important reference value for understanding the mechanism of HDs and designing structural parameters of SiNWs for high-performance hydrovoltaic devices.

CuSCN/Si heterojunction near-infrared photodetector based on micro/nano light-trapping structure

In this paper, high-performance CuSCN/Si heterojunction near-infrared photodetectors were successfully prepared using nanoscale light-trapping optical structures. Various light-trapping structures of ortho-pyramids, inverted pyramids and silicon nanowires were prepared on silicon substrates. Then, CuSCN films were spin-coated on silicon substrates with high crystalline properties for the assembly of CuSCN/Si photodetectors. Their reflectance spectra and interfacial passivation properties were characterized, demonstrating their superiority of light-trapping structures in high light response. Under the irradiation of 980 nm near-infrared light, a maximum responsivity of 2.88 A W^-1at -4 V bias and a specific detectivity of 5.427 × 10¹⁰Jones were obtained in the CuSCN/Si heterojunction photodetectors prepared on planner silicon due to 3.6 eV band gap of CuSCN. The substrates of the light-trapping structure were then applied to the CuSCN/Si heterojunction photodetectors. A maximum responsivity of 10.16 A W^-1and a maximum specific detectivity of 1.001 × 10¹¹Jones were achieved under the 980 nm near-infrared light irradiation and -4 V bias, demonstrating the advanced performance of CuSCN/Si heterojunction photodetectors with micro-nano light-trapping substrates in the field of near-infrared photodetection compared to other silicon-based photodetectors.

Facilely Achieved Self-Biased Black Silicon Heterojunction Photodiode with Broadband Quantum Efficiency Approaching 100

Photodiodes are fundamental components in modern optoelectronics. Heterojunction photodiodes, simply configured by two different contact materials, have been a hot research topic for many years. Currently reported self-biased heterojunction photodiodes routinely have external quantum efficiency (EQE) significantly below 100% due to optical and electrical losses. Herein, an approach that virtually overcomes this 100% EQE challenge via low-aspect-ratio nanostructures and drift-dominated photocarrier transport in a heterojunction photodiode is proposed. Broadband near-ideal EQE is achieved in nanocrystal indium tin oxide/black silicon (nc-ITO/b-Si) Schottky photodiodes. The b-Si comprises nanostalagmites which balance the antireflection effect and surface morphology. The built-in electric field is explored to match the optical generation profile, realizing enhanced photocarrier transport over a broadband of photogeneration. The devices exhibit unprecedented EQE among the reported leading-edge heterojunction photodiodes: average EQE surpasses ≈98% for wavelengths of 570-925 nm, while overall EQE is greater than ≈95% from 500 to 960 nm. Further, only elementary fabrication techniques are explored to achieve these excellent device properties. A heart rate sensor driven by nanowatt faint light is demonstrated, indicating the enormous potential of this near-ideal b-Si photodiode for low power consuming applications.

Brush-Paintable Black Electrodes for Poly(vinylidene fluoride)-Based Flexible Piezoelectric Devices

We investigated simple and unrestricted brush-paintable black electrodes for poly(vinylidene fluoride) (PVDF)-based artistic flexible piezoelectric devices. The conductive black ink for paintable electrodes was synthesized by mixing poly(3,4-ethylene dioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) and typical black ink and optimizing the mixing ratio. At an optimal mixing ratio, the brush-paintable black electrodes showed a sheet resistance of 151 Ω/sq and high coatability for flexible piezoelectric devices. Noticeably, higher black ink ratios increased adhesion forces, while diminished the shear flow of the conductive black ink. In addition, the optimized conductive black electrode exhibited an outstanding level of mechanical flexibility due to good adhesion between the black electrode and the PVDF substrate. During the repeated inner/outer bending fatigue tests with high strain, no resistance change confirmed the outstanding flexibility of the brush-paintable conductive electrode. As a promising application of the brush-paintable optimized black electrode, we suggested highly flexible piezoelectric devices that can be used. A PVDF-based piezoelectric speaker and a generator with the brush-paintable black electrode showed acoustic and output signal values approximate to those of metallic electrodes fabricated by vacuum-based high-cost thermal evaporators. Our experiment demonstrated a cost-efficient and simple process for fabricating brush-paintable electrodes, applicable to the flexible PVDF-based piezoelectric devices.

Interface Engineering of a Silicon/Graphene Heterojunction Photodetector via a Diamond-Like Carbon Interlayer

Silicon/graphene nanowalls (Si/GNWs) heterojunctions with excellent integrability and sensitivity show an increasing potential in optoelectronic devices. However, the performance is greatly limited by inferior interfacial adhesion and week electronic transport caused by the horizontal buffer layer. Herein, a diamond-like carbon (DLC) interlayer is first introduced to construct Si/DLC/GNWs heterojunctions, which can significantly change the growth behavior of the GNWs film, avoiding the formation of horizontal buffer layers. Accordingly, a robust diamond-like covalent bond with a remarkable enhancement of the interfacial adhesion is yielded, which notably improves the complementary metal oxide semiconductor compatibility for photodetector fabrication. Importantly, the DLC interlayer is verified to undergo a graphitization transition during the high-temperature growth process, which is beneficial to pave a vertical conductive path and facilitate the transport of photogenerated carriers in the visible and near-infrared regions. As a result, the Si/DLC/GNWs heterojunction detectors can simultaneously exhibit improved photoresponsivity and response speed, compared with the counterparts without DLC interlayers. The introduction of the DLC interlayer might provide a universal strategy to construct hybrid interfaces with high performance in next-generation optoelectronic devices.

Melt-grown large-sized Cs2TeI6 crystals for X-ray detection

Large-sized lead-free perovskite Cs₂TeI₆ shows an X-ray sensitivity of 27.8 μC Gy⁻¹ cm⁻² with a detection limit as low as 72.5 nGy s⁻¹.

Valence-State Controllable Fabrication of Cu2-xO/Si Type-II Heterojunction for High-Performance Photodetectors

Cuprite, nominally cuprous oxide (Cu₂O) but more correctly Cu_2-xO, is widely used in optoelectronic applications because of its natural p-type, nontoxicity, and abundant availability. However, the photoresponsivity of Cu₂O/Si photodetectors (PDs) has been limited by the lack of high-quality Cu_2-xO films. Herein, we report a facile room-temperature solution method to prepare high-quality Cu_2-xO films with controllable x value which were used as hole selective transport layers in crystalline n-type silicon-based heterojunction PDs. The detection performance of Cu_2-xO/Si PDs exhibits a remarkable improvement via reducing the x value, resulting in the optimized PDs with high responsivity of 417 mA W^-1 and fast response speed of 1.3 μs. Furthermore, the performance of the heterojunction PDs can be further improved by designing the pyramidal silicon structure, with enhanced responsivity of 600 mA W^-1 and response speed of 600 ns. The superior photodetecting performance of Cu_2-xO/n-Si heterojunctions is attributed to (i) the matched energy level band alignment, (ii) the low trap states in high-quality Cu₂O thin films, and (iii) the excellent light trapping. We expect that the low-cost, highly efficient solution process would be of great convenience for large-scale fabrication of the Cu_2-xO thin films and broaden the applications of Cu_2-xO-based optoelectronic devices.

Significantly Enhancing Response Speed of Self-Powered Cu2ZnSn(S,Se)4 Thin Film Photodetectors by Atomic Layer Deposition of Simultaneous Electron Blocking and Electrode Protective Al2O3 Layers

Kesterite Cu₂ZnSn(S,Se)₄ (CZTSSe) thin film is a promising material for optoelectronic devices. In this work, we fabricate Mo/CZTSSe/CdS/ZnO/ITO (ITO, indium tin oxide) heterojunction photodetectors with favorable self-powered characteristics. The photodetector exhibits exceptional high-frequency photoresponse performance whose -3 dB bandwidth and rise/decay time have reached 1 MHz and 240/340 ns, respectively. For further improvement, ultrathin Al₂O₃ layer prepared via atomic layer deposition (ALD) process is introduced at the Mo/CZTSSe interface. The influence of ALD-Al₂O₃ layer thickness and its role on the photoresponse performance are investigated in detail. The interfacial layer proved to serve as a protective layer preventing selenization of Mo electrode, resulting in the reduction of MoSe₂ transition layer and the decrease of series resistance of the device. Accordingly, the -3 dB bandwidth is remarkably extended to 3.5 MHz while the rise/decay time is dramatically improved to 60/77 ns with 16 cycles of ALD-Al₂O₃ layer, which is 4-5 orders of magnitude faster than the other reported CZTSSe photodetectors. Simultaneously, it is revealed that the ALD-Al₂O₃ interfacial layer acts as an electron blocking layer which leads to the effective suppression of carrier recombination at the rear surface. Consequently, the responsivity and detectivity are enhanced in the entire range while the maximum values are up to 0.39 AW^-1 and 2.04 × 10¹¹ Jones with 8 cycles of ALD-Al₂O₃, respectively. Finally, the CZTSSe photodetector is successfully integrated into a visible light communication system and obtains a satisfying transfer rate of 2 Mbps. These results indicate the satisfying performance of CZTSSe-based thin film photodetectors with great potential applications for communication.

Atomic-Layer Deposition-Assisted Double-Side Interfacial Engineering for High-Performance Flexible and Stable CsPbBr3 Perovskite Photodetectors toward Visible Light Communication Applications

Self-powered photodetectors (PDs) based on inorganic metal halide perovskites are regarded as promising alternatives for the next generation of photodetectors. However, uncontrollable film growth and sluggish charge extraction at interfaces directly limit the sensitivity and response speed of perovskite-based photodetectors. Herein, by assistance of an atomic layer deposition (ALD) technique, CsPbBr₃ perovskite thin films with preferred orientation and enlarged grain size are obtained on predeposited interfacial modification layers. Thanks to improved film quality and double side interfacial engineering, the optimized CsPbBr₃ (Al₂ O₃ /CsPbBr₃ /TiO₂ , ACT) perovskite PDs exhibit outstanding performance with ultralow dark current of 10^-11 A, high detectivity of 1.88 × 10¹³ Jones and broad linear dynamic range (LDR) of 172.7 dB. Significantly, excellent long-term environmental stability (ambient conditions >100 d) and flexibility stability (>3000 cycles) are also achieved. The remarkable performance is credited to the synergistic effects of high carrier conductivity and collection efficiency, which is assisted by ALD modification layers. Finally, the ACT PDs are successfully integrated into a visible light communication system as a light receiver on transmitting texts, showing a bit rate as high as 100 kbps. These results open the window of high performance all-inorganic halide perovskite photodetectors and extends to rational applications for optical communication.

Light Trapping in Conformal Graphene/Silicon Nanoholes for High-Performance Photodetectors

Hybrid graphene/silicon heterojunctions have been widely utilized in photodetectors because of their unique characteristics of high sensitivity, fast response, and CMOS compatibility. However, the photoresponse is restricted by the high reflectance of planar silicon (up to 50%). Herein, an improved graphene/Si detector with excellent light absorption performance is proposed and demonstrated by directly growing graphene on the surface of silicon nanoholes (SiNHs). It is shown that the combination of SiNHs with conformal graphene provides superior interfaces for efficient light trapping and transport of the photoexcited carriers. A high absorption of up to 90% was achieved, and the conformal graphene/SiNH-based photodetectors exhibited a higher photoresponsivity (2720 A/W) and faster response (∼6.2 μs), compared with the counterpart of the planar graphene/Si, for which the corresponding values are 850 A/W and 51.3 μs. These results showcase the vital role of the material morphology in optoelectronic conversion and pave the way to explore novel high-performance heterojunction photodetectors.

Robust Photodetectable Paper from Chemically Exfoliated MoS2-MoO3 Multilayers

Photodetectors, which are capable of detecting light with varied wavelength, have nowadays been widely applied onto emerging fields such as security, entertainment, healthcare, environment, and so on. As the one with a two-dimensional layered structure, molybdenum disulfide (MoS₂) possesses striking optical and electrical properties that can be used in photodetecting, yet the challenges remain in terms of material processing, device fabrication simplicity, and enhancement of overall photodetection performance. In this work, a photodetectable paper based on a mixture of double-phased MoS₂ (1T and 2H) and MoO₃ was successfully fabricated through a straightforward route, that is, chemical exfoliation and deposition of MoS₂ powder on a flexible cellulose ester membrane, followed by inkjet-printed PEDOT:PSS as electrodes. The obtained device shows varied sensitivity to the light with different wavelengths. Compared with that under green and red lights, the prepared photodetector has the highest internal quantum efficiency (0.063%) and responsivity (0.134 mA W^-1), while having longest response/recovery time (17.5/15.3 s) when illuminated with purple light (405 nm). The achieved responsivity is much higher than other reported liquid exfoliation- and solution-derived MoS₂ photodetectors. This is ascribed to (1) the enhanced photoelectron generation caused by both MoS₂ and MoO₃ and (2) the good electric conductivity and efficient charge transport caused by the metallic 1T MoS₂. This work demonstrates the feasibility of fabricating the MoS₂-based photodetector with excellent performance through a simple exfoliation/filtration and inject printing route, and the detailed study on the response to light with different wavelengths unveils the interaction between the device and the incident light, further broadening the potential applications of such design.

Significantly Enhanced Detectivity of CIGS Broadband High-Speed Photodetectors by Grain Size Control and ALD-Al2O3 Interfacial-Layer Modification

The Cu(In,Ga)Se₂ (CIGS) thin film has been commercialized as solar cells with great success, but its application for photodetectors still faces some practical challenges, including low detectivity and long response time. In this paper, the structure of the Mo/CIGS/CdS/ZnO/ITO heterojunction has been fabricated, and satisfactory performances of high detectivity and fast response time have been achieved by suppressing the dark current and enhancing the carrier mobility. The controllable growth of CIGS grains is accomplished through optimizing the selenization process, demonstrating that bigger grain sizes resulted in higher carrier mobility and better response characteristics. Particularly, the high rise/decay speed of 3.40/6.46 μs is achieved. Furthermore, the interface of the CIGS/CdS heterojunction has been modified by the Al₂O₃ layer via the atomic-layer deposition (ALD) process. The dark current of the device is effectively suppressed by the ALD-Al₂O₃ layer, which remarkably drops from ∼10^-7 to ∼10^-9 A. As a consequence, the detectivity rises from 3.08 × 10¹¹ to 1.84 × 10¹² Jones. In addition, the ALD-Al₂O₃ layer shows a protective effect as well, which is positive for photoelectrical conversion. Besides, the wide linear dynamic range of 102.1 dB and large -3 dB bandwidth of 78 kHz are acquired. This work suggests that the CIGS-based heterojunction has great potential for high-performance thin-film photodetectors.

High-Performance Visible-Blind Ultraviolet Photodetector Based on IGZO TFT Coupled with p-n Heterojunction

A visible-blind ultraviolet (UV) photodetector was designed based on a three-terminal electronic device of thin-film transistor (TFT) coupled with two-terminal p-n junction optoelectronic device, in hope of combining the beauties of both of the devices together. Upon the uncovered back-channel surface of amorphous indium-gallium-zinc-oxide (IGZO) TFT, we fabricated PEDOT:PSS/SnO _x/IGZO heterojunction structure, through which the formation of a p-n junction and directional carrier transfer of photogenerated carriers were experimentally validated. As expected, the photoresponse characteristics of the newly designed photodetector, with a photoresponsivity of 984 A/W at a wavelength of 320 nm, a UV-visible rejection ratio up to 3.5 × 10⁷, and a specific detectivity up to 3.3 × 10¹⁴ Jones, are not only competitive compared to the previous reports but also better than those of the pristine IGZO phototransistor. The hybrid photodetector could be operated in the off-current region with low supply voltages (<0.1 V) and ultralow power dissipation (<10 nW under illumination and ∼0.2 pW in the dark). Moreover, by applying a short positive gate pulse onto the gate, the annoying persistent photoconductivity presented in the wide band gap oxide-based devices could be suppressed conveniently, in hope of improving the response rate. With the terrific photoresponsivity along with the advantages of photodetecting pixel integration, the proposed phototransistor could be potentially used in high-performance visible-blind UV photodetector pixel arrays.

Dopant-Free and Carrier-Selective Heterocontacts for Silicon Solar Cells: Recent Advances and Perspectives

By combining the most successful heterojunctions (HJ) with interdigitated back contacts, crystalline silicon (c-Si) solar cells (SCs) have recently demonstrated a record efficiency of 26.6%. However, such SCs still introduce optical/electrical losses and technological issues due to parasitic absorption/Auger recombination inherent to the doped films and the complex process of integrating discrete p+- and n+-HJ contacts. These issues have motivated the search for alternative new functional materials and simplified deposition technologies, whereby carrier-selective contacts (CSCs) can be formed directly with c-Si substrates, and thereafter form IBC cells, via a dopant-free method. Screening and modifying CSC materials in a wider context is beneficial for building dopant-free HJ contacts with better performance, shedding new light on the relatively mature Si photovoltaic field. In this review, a significant number of achievements in two representative dopant-free hole-selective CSCs, i.e., poly(3,4-ethylene dioxythiophene):poly(styrenesulfonate)/Si and transition metal oxides/Si, have been systemically presented and surveyed. The focus herein is on the latest advances in hole-selective materials modification, interfacial passivation, contact resistivity, light-trapping structure and device architecture design, etc. By analyzing the structure-property relationships of hole-selective materials and assessing their electrical transport properties, promising functional materials as well as important design concepts for such CSCs toward high-performance SCs have been highlighted.

Omnidirectional Harvesting of Weak Light Using a Graphene Quantum Dot-Modified Organic/Silicon Hybrid Device

Despite great improvements in traditional inorganic photodetectors and photovoltaics, more progress is needed in the detection/collection of light at low-level conditions. Traditional photodetectors tend to suffer from high noise when operated at room temperature; therefore, these devices require additional cooling systems to detect weak or dim light. Conventional solar cells also face the challenge of poor light-harvesting capabilities in hazy or cloudy weather. The real world features such varying levels of light, which makes it important to develop strategies that allow optical devices to function when conditions are less than optimal. In this work, we report an organic/inorganic hybrid device that consists of graphene quantum dot-modified poly(3,4-ethylenedioxythiophene) polystyrenesulfonate spin-coated on Si for the detection/harvest of weak light. The hybrid configuration provides the device with high responsivity and detectability, omnidirectional light trapping, and fast operation speed. To demonstrate the potential of this hybrid device in real world applications, we measured near-infrared light scattered through human tissue to demonstrate noninvasive oximetric photodetection as well as characterized the device's photovoltaic properties in outdoor (i.e., weather-dependent) and indoor weak light conditions. This organic/inorganic device configuration demonstrates a promising strategy for developing future high-performance low-light compatible photodetectors and photovoltaics.

Stable ultra-fast broad-bandwidth photodetectors based on α-CsPbI3 perovskite and NaYF4:Yb,Er quantum dots

Photodetectors (PDs), especially those that respond in the infrared region, are highly desirable and have a wide range of applications ranging from cell phones, cameras, and home electronics to airplanes and satellites. Herein, we designed and fabricated PDs based on air-stable α-CsPbI₃ QDs and an up-conversion material (NaYF₄:Yb,Er QDs) using a facial low temperature spin-coating method. When the α-CsPbI₃ QDs are surface-modified using NaYF₄:Yb,Er QDs, their optical response is extended to the NIR region to allow broadband application from the UV to visible to NIR region (260 nm-1100 nm). The optoelectronic properties and compositional stability of the devices were also studied in detail. From the results, the PDs are capable of broad-bandwidth photodetection from the deep UV to NIR region (260 nm-1100 nm) with good photoresponsivity (R, 1.5 A W^-1), high on/off ratio (up to 10⁴) and very short rise/decay time (less than 5 ms/5 ms). It was found that the photoresponsivity performance of the PDs in this work is better than that of all the other previously reported perovskite QD-based PDs with a lateral device structure. Furthermore, the device performance shows very little degradation over the course of 60 days of storage under ambient conditions. The combination of remarkable stability, high performance broad-bandwidth photodetection, and easy fabrication suggest that these QDs are a very promising semiconducting candidate for optoelectronic applications.

Topological Crystalline Insulator SnTe/Si Vertical Heterostructure Photodetectors for High-Performance Near-Infrared Detection

Due to the gapless surface state and narrow bulk band gap, the light absorption of topological crystalline insulators covers a broad spectrum ranging from terahertz to infrared, revealing promising applications in new generation optoelectronic devices. To date, the photodetectors based on topological insulators generally suffer from a large dark current and a weaker photocurrent especially under the near-infrared lights, which severely limits the practical application of devices. Owing to the lower excitation energy of infrared lights, the photodetection application of topological crystalline insulators in the near-infrared region relies critically on understanding the preparation and properties of their heterostructures. Herein, we fabricate the high-quality topological crystalline insulator SnTe film/Si vertical heterostructure by a simple physical vapor deposition process. The resultant heterostructure exhibits an excellent diode characteristic, enabling the construction of high-performance near-infrared photodetectors. The built-in electric field at SnTe/Si interface enhances the absorption efficiency of near-infrared lights and greatly facilitates the separation of photogenerated carriers, making the device capable of operating as a self-driven photodetector. The as-grown SnTe film acts as the hole transport layer in heterostructure photodetectors, promoting the transport of holes to electrode and reducing electron-hole recombination effectively. These merits enable the SnTe/Si heterostructure photodetector to have a high responsivity of 2.36 AW^-1, a high detectivity of 1.54 × 10¹⁴ Jones, and a large bandwidth of 10⁴ Hz in the near-infrared wavelength, which makes the detector have a promising market in novel device applications.

Phenomenal Ultraviolet Photoresponsivity and Detectivity of Graphene Dots Immobilized on Zinc Oxide Nanorods

A combination of dimensionally reduced graphene quantum dots (GQDs) having edge effects and the vertically aligned ZnO nanorods shows highly selective visible-blind ultraviolet (UV) sensing. The GQD immobilized ZnO nanorod heterostructure shows remarkable responsivity of ∼6.62 × 10⁴ A/W and detectivity of ∼1.78 × 10¹⁵ Jones under 365 nm (10 μW) incident light and 2 V bias potential with high stability of at least 5 cycles, fast response time of 2.14 s, and recovery time of 0.91 s. The grain boundary assisted electron transport across GQDs was calculated from the normalized absorption below bandgap. The highest UV responsivity and detectivity were found to be proportional to the lowest trap state density at the grain boundaries (Q_t) and minimum grain boundary potential (E_b). For the best GQD, Q_t and E_b were found to be ∼4 × 10¹³ cm^-2 and 0.4 meV, respectively. The phenomenal performance of ZnO-GQD heterostructure is attributed to the efficient immobilization of GQDs on ZnO nanorods and the idea of employing GQDs as photosensitizers than solely as electron transporting medium. The efficiency of GQDs is superior to carbon quantum dots (CQDs) containing minimal graphitic domains, and graphene oxide (GO) or reduced graphene oxide (rGO) having larger dimensions preventing their immobilization on ZnO nanorods.