Nonradiative Defects Research Articles

Understanding and Controlling the Formation of Nonradiative Defects in Blue Organic Triplet Emitters

Phosphorescent organic light-emitting devices (PHOLEDs) suffer from destructive molecular processes due to triplet-polaron and triplet-triplet annihilation. These processes are energetically driven and hence are particularly active in decreasing the lifetime of blue PHOLEDs. It has recently been shown that increasing triplet radiative rates via the Purcell effect effectively extends the device operational lifetime by reducing the triplet radiative lifetime, thus decreasing their density and the probability of triplet-annihilation reactions. We provide an analytical framework using Marcus theory to explain the observed, approximately exponential relationship between exciton energy and device lifetime. From transient drift-diffusion dynamics, we show that the Purcell effect reduces the exciton density in the steady state and increases the photoluminescent yield, thereby reducing defect generation rates and extending the device lifetime. We control the radiative rate of excitons in microcavities, thereby connecting the exciton energy and decay rates with the observed device lifetime. The device lifetime is shown to follow a power-law dependence on the Purcell factor (PFm) with m=1.5 to 2.5, dependent on the TTA-to-TPA ratio and photoluminescence quantum yield. From our analysis, a fivefold increase in PF has the potential to extend the blue PHOLED lifetime by up to 2 orders of magnitude, making the blue PHOLED lifetime comparable to that of state-of-the-art green PHOLEDs. Published by the American Physical Society 2024

Design and Performance of an InAs Quantum Dot Scintillator with Integrated Photodetector.

A new scintillation material composed of InAs quantum dots (QDs) hosted within a GaAs matrix was developed, and its performance with different types of radiation is evaluated. A methodology for designing an integrated photodetector (PD) with a low defect density and that is optically matched to the QD's emission spectrum is introduced, utilizing an engineered epitaxial InAlGaAs metamorphic buffer layer. The photoluminescence (PL) collection efficiency of the integrated PD is examined using two-dimensional scanning laser excitation. The detector response to 5.5 MeV α-particles and 122 keV photons is presented. Yields of 13 electrons/keV for α-particles and 30-60 electrons/keV for photons were observed. The energy resolution of 12% observed with α-particles was mainly limited by noise- and geometry-related optical losses. The radiation hardness of an InAs QDs hosted within GaAs and a wider band gap AlGaAs ternary alloy was studied under a 1 MeV proton implantation up to a 1014 cm-2 dose. The integrated PL responses were compared to evaluate PL quenching due to non-radiative defects. The QDs embedded in the AlGaAs demonstrated improved radiation hardness compared to QDs in the GaAs matrix and in the InGaAs quantum wells.

Enhanced amplified spontaneous emission performance of inorganic perovskite by additive engineering

All-inorganic perovskites have become promising optical gain medium due to excellent optical properties. For CsPbX3 thin films, optical losses caused by uneven morphology and non-radiative defects can hinder amplified spontaneous emission (ASE) performance. Here, we take advantage of additive engineering strategy to simultaneously control the morphology and defect states of CsPbBrxI3-x films via introducing Polysorbate-20 (PS20) into perovskite precursor. The optical gain coefficient of the CsPbBrxI3-x film increased from 491.1 cm−1 to 1252 cm−1 and ASE threshold decreased to 4.72 μJ/cm2. Moreover, the optimized perovskite film exhibited excellent linear polarization characteristics with high degree of polarization (DOP) of 88 %. Our research highlights the importance of defect passivation and morphology control to improve ASE performance.

Polycrystalline inclusion-free growth of thick, lattice-matched SiGeC with high substitutional Carbon concentrations up to 2%

Lattice-matched SiGeC with ~20% of Ge was grown at 550°C, 10 Torr on a 300 mm Si substrate in an industrial standard Reduced Pressure Chemical Vapor Deposition reactor using commercially available Si2H6/GeH4/SiH3CH3 precursors. Thicknesses exceeding 250 nm resulted in cluster formation in SiGeC with [C]Sub~2.0% and [C]Int~0.4%, with a surface density up to 6.13x106 µm-2. Room temperature photoluminescence measurements showed that the clusters were non-radiative defects and Transmission Electron Microscopy, using the ASTAR system, proved they were polycrystalline with random orientation. Cluster-free growth was achieved for 1 µm thick SiGeC with [C]Sub~1.0% and no interstitial carbon atoms, however, without lattice-matched growth on a Si substrate. Injecting HCl during a co-flow process resulted in a smooth surface with a RMS roughness of 0.23 nm and a reduction of [C]Intfrom ~0.7% down to ~0.1%, close to the detection limit of X-ray Photoelectron Spectroscopy at 0.1%. This led to a significant cluster surface density reduction down to 1.15x104 µm-2. The injection of HCl caused an increase in the Ge concentration from 19.7% up to 28.9% and a non-lattice-matched growth. A Cyclic Deposition Etch (CDE) process resulted in no [C]Int reduction, but significantly reduced the cluster surface density down to 4.60x104 µm-2. CDE-grown SiGeC was lattice-matched to the Si substrate and yielded a smooth surface with a RMS roughness of 0.22 nm. This enabled the growth of high crystalline quality, thick, lattice-matched layers on a 300 mm Si substrate with material properties beyond pure Si.

Ultra-dense Green InGaN/GaN Nanoscale Pixels with High Luminescence Stability and Uniformity for Near-Eye Displays.

Ultra-dense (>4,000 pixels per inch) and highly stable full-color III-nitride nanoscale pixels are crucial for near-eye display technologies like virtual and augmented-reality glasses. In this context, InGaN-based long wavelength green microscale light-emitting diodes face major bottlenecks, such as low efficiency and inadequate wavelength stability. These challenges are associated with the presence of both nonradiative surface defects and the strain induced quantum-confined Stark effect. Herein, we report nanoscale pixelation of green InGaN/GaN LEDs incorporating strain-engineered ultra-dense nanowire (NW) arrays, corresponding to ∼36,000 pixels per inch. The NW pixel arrays exhibit a stable peak wavelength emission at ∼500 nm for over 3 orders of magnitude of injection current densities (from ∼4 A/cm2 to ∼1 kA/cm2). The observed wavelength stability enhancement (a reduced blue-shift of just ∼4 nm) directly results from the suppressed built-in electric field achieved by strain relaxation of the axial multi quantum wells in the NWs. Finite difference time domain simulations show that emission of the pixel array is significantly increased owing to the enhanced spontaneous emission rate (characterized by a high Purcell factor of ≈2) of the ultra-dense NWs. We have demonstrated top-down NWs, where each NW (diameter ranging down to 200 nm) shows excellent uniformity and light output characteristics in direct contrast to bottom-up grown NW heterostructures. The results of this study establish a viable route for realizing nanoscale pixels with high luminescence stability and wafer-scale uniformity with high (>20%) indium composition InGaN/GaN LED heterostructures, for next-generation near-eye displays.

Regulating thermal management by a CsPbClBr2/Ag hybrid microcavity for stable room temperature blue lasing with low threshold

Realization of long-term stable lasing from all-inorganic perovskite supercrystals is highly desirable for practical applications in optoelectronic devices. However, lasing from perovskite supercrystals excited by continuous wave laser light remains a challenge due to the photoluminescence degradation induced by thermal accumulation. Here, we report highly stable lasing with low threshold fom a CsPbClBr2 supercrystal placed on a thin Ag film, which form a CsPbClBr2/Ag microcavity, by managing the thermal distribution inside the CsPbClBr2 supercrystal. Combined numerical simulations and lifetime measurements, the localized electric field in such a hybrid microcavity leads to a spatially localized temperature distribution, which plays a crucial role in suppressing the thermal accumulation on the surface and in eliminating non-radiative recombination defects. The effective thermal management in the hybrid microcavity renders highly stable lasing with low threshold under the irradiation of continuouw wave laser light. Our findings provide a feasible and universal approach to the development of long-term stable perovskite laser.

Efficient and stable perovskite solar cells via oxalic acid doped SnO2 nanocrystals with surface-defect passivation

The electron extraction and transfer play a crucial role in high performance of perovskite solar cells (PSCs). Tin dioxide (SnO2), with the high electrical conductivity and low photocatalytic activity, has been reported to be one of the most advantageous electron-transporting layers (ETL) in PSCs. However, a large number of non-radiative recombination defects have been reported in SnO2, which are attributed to the low tunability and lower dispersibility. Here, we propose a ligand-assisted tuning strategy based on the oxalic acid (OA) modification to control the SnO2 film and interfacial structure. This strategy can effectively inhibit the particle aggregation of SnO2 film. In addition, the bonding interaction between CO in the ligand and Sn in SnO2 and Pb atoms in the perovskite reduces the interfacial contact impedance and enhances the electron extraction. As a result, an impressive PCE of 22.68 %, a fill factor exceeding 0.82 and a Voc of 1.15 V were successfully obtained. In addition, the unencapsulated PSCs can maintain an initial efficiency of 93 % upon exposure to ambient air for 500 h.

A-Site Cations Impact on Nonradiative Recombination, Mobility, and Defect Dynamics in Sn-Based Perovskites.

Sn-based perovskites with different cations in the A-site exhibit distinct electronic structures and dynamic properties. By utilizing time-dependent density functional theory and nonadiabatic molecular dynamics, we demonstrate that larger FA cations decrease wave function overlap between initial and final states and slow down nuclear motion. In the case of FASnI3, this alteration decreases the nonadiabatic coupling and increases the nonradiative electron-hole recombination time by 130% and 76%, respectively, compared to CsSnI3 and MASnI3 (CH3NH3SnI3). Furthermore, A-site modification significantly improves electron mobility and changes the properties of defects in FASnI3 (HC(NH2)2SnI3), which achieves higher electron mobility through a polar optical phonon-dominated scattering mechanism and exhibits higher defect formation energy and migration barriers of A-site cations due to increased steric hindrance, relative to CsSnI3 and MASnI3. These results emphasize the critical function of A-site cation substitution in controlling nonradiative recombination dynamics, electron mobility, and defect characteristics in Sn-based perovskites and provide theoretical insights for the advancement of novel lead-free perovskite materials.

Highly efficient blue light-emitting diodes based on mixed-halide perovskites with reduced chlorine defects.

Perovskite light-emitting diodes (PeLEDs) provide excellent opportunities for low-cost, color-saturated, and large-area displays. However, the performance of blue PeLEDs lags far behind that of their green and red counterparts. Here, we show that the external quantum efficiencies (EQEs) of blue PeLEDs scale linearly with the photoluminescence quantum yields (PL QYs) of CsPb(BrxCl1-x)3 nanocrystals emitting at 460 to 480 nm. The recombination efficiency of carriers is highly sensitive to the chlorine content and the related deep-level defects in nanocrystals, causing notable EQE drops even with minor increases in chlorine defects. Minor adjustments of chlorine content through rubidium compensation on the A-site effectively suppress the formation of nonradiative defects, improving PL QYs while retaining desirable bandgaps for blue-emitting nanocrystals. Our PeLEDs with record-high efficiencies span the blue spectrum, achieving peak EQEs of 12.0% (460 nm), 16.7% (465 nm), 21.3% (470 nm), 24.3% (475 nm), and 26.4% (480 nm). This work exemplifies chlorine-defect control as a key design principle for high-efficiency blue PeLEDs.

Porous PbBr2 films modulation by indium tribromide additive for the fabrication of SnO2-based CsPbBr3 perovskite solar cells

The achievement of complete conversion of PbBr2 films presents a significant challenge in the development of CsPbBr3 films with consistent growth, comprehensive coverage, and controllable components. To address this challenge, introducing a porous structure in the planar PbBr2 film is advantageous for facilitating the immersion of CsBr precursor, thereby reducing impurity phase formation and mitigating strain caused by the film volume expansion. In order to accomplish this, indium tribromide (InBr3) was employed as an additive and the InBr3(DMF)3 adduct was utilized to expedite the release of organic molecules in PbBr2(DMF), resulting in the transformation of planar PbBr2 film into porous structures. The growth orientation of PbBr2 crystals was altered by this transformation, effectively suppressing the generation of metallic Pb impurities in the film. Additionally, it not only optimizes the morphology of CsPbBr3 film but also reduces impurity phase. As a result, the InBr3:CsPbBr3 perovskite solar cell achieved an efficiency of 7.28 %. The majority of In3+ ions were concentrated near the buried interface between SnO2 and InBr3:CsPbBr3, leading to significant improvements in both non-radiative recombination defect states within the perovskite film and electron injection and collection capabilities within the device.

Ionic-confining-assisted multiple-mode tunable light emitting of carbon nanodots

Multiple-mode light emitting in one material system is tremendous desirable for various applications. Herein, we have developed an ionic crystal confining strategy to prepare the carbon nanodots (CDs) with quadruple-mode light emitting and demonstrated their promising application in information anti-counterfeiting via optical logic gates. In detail, the quadruple-mode light emitting of CDs (QM-CDs) are prepared with the citric acid and urea with NaOH matrix via microwave-assisted polymerization. Mechanically, the high-density ionic bonds stemmed from the NaOH ionic-crystal can effectively inactivate nonradiative defect centers, stabilize triplet excitons, increase absorption cross-section and boost resonance energy transfer, evoking the outstanding solid-state fluorescence, upconversion photoluminescence (UCPL), phosphorescence, and chemiluminescence simultaneously. Meanwhile, the isolated NaOH matrix can promote the confining aggregation of CDs, leading to the redshifted emission wavelength and endowing the light emitting with tunable wavelength. With the excitability of logic functions between the light emitting and controlled excitation, the programmable multiple-inputs logic gates are established with the QM-CDs, enabling the application in high-throughput logical operations and information anti-counterfeiting. This research provides a new insight into the synthesize of multiple-mode luminescent CDs, and thus promote the applications of nanomaterials in intelligent encryption and anti-counterfeiting.

Highly Stable O‐Tolylbiguanide‐CsPbI3 Quantum Dots and Light‐Emitting Diodes by Synergistic Supramolecular Passivation

AbstractDeveloping effective strategy to passivate surface defects in quantum dots (QDs) is critical to achieving high‐efficiency and long‐life perovskite light‐emitting diodes (LEDs). Here, the supramolecular interaction underpinning of organic‐inorganic components is exploited and a facile method is proposed to generate multiple‐hydrogen‐bonded supramolecular‐perovskite crystal structures on QD surfaces by introducing O‐Tolylbiguanide (O‐Tg) during QD synthesis, enabling bright, conductive, and water‐resistant CsPbI3 QDs. Compared with commonly used oleic acid and oleylamine ligands, the biguanide functional group in O‐Tg not only forms multiple hydrogen bond interactions with lead halide octahedra passivating both bridging‐ and terminal‐halogen ion defects, but also compatibly occupies the A‐site position stabilizing the crystal structure simultaneously. With fewer nonradiative defects and introduced hydrophobic benzene rings preventing eroding of polar molecules, CsPbI3 QDs exhibit remarkable photoluminescence quantum yields of 96%, and their film can be submerged in water for 30 h without degrading. The corresponding LEDs display a high external quantum efficiency (21.2%) and offer superior operational stability with a lifetime (T90) of 25 h at a constant current density as high as 50 mA cm−2.

Additive engineering enabled non-radiative defect passivation with improved moisture-resistance in efficient and stable perovskite solar cells

Perovskite solar cells have emerged as promising candidates in the photovoltaic industry owing to their high efficiencies and low production costs. However, their commercial viability has been hampered by issues related to long-term environmental and operational stability, and their efficiency is lower than the Shockley–Queisser (SQ) limit. In this study, we explored a groundbreaking approach to enhance the efficiency and stability of CH3NH3PbI3 perovskite solar cells via the additive engineering of tetraphenylphosphonium chloride (TPPP(Cl)). By introduction of TPPP(Cl) into perovskite precursor, we demonstrated a notable amelioration in the photovoltaic performance of respective device. The presence of TPPP(Cl) enhances the crystallinity of the perovskite film, and the Cl from TPPP(Cl) can passivate halide ion defects, resulting in reduced defect density and improved charge carrier mobility. This in turn, leads to a substantial increase in power conversion efficiency, making perovskite solar cells a more competitive option for renewable energy applications. Furthermore, our research delves into the remarkable stability enhancement achieved through the incorporation of TPPP(Cl), as the champion device retained 89 % of its initial PCE for over 30 days after being placed in an ambient environment without any encapsulation. Thus, we propose that careful regulation of the concentration of TPPP(Cl) significantly increases the resistance of the device to moisture and heat, resulting in prolonged operational lifetimes.

Infrared Light-Emitting Diodes Based on Chirality-Sorted Carbon Nanotube Films.

An important goal in carbon nanotube optoelectronics is to achieve a high-performance near-infrared light source. But there are still many challenges such as the purity of single-walled carbon nanotube (SWCNT) chirality, nonradiative defects, thin-film quality, and device structure design. Here, we realize infrared light-emitting diodes (LEDs) based on chirality-sorted (10, 5) SWCNT network films, which operate at a low bias voltage and emit at a telecom O band of 1290 nm. Asymmetric palladium (Pd) and hafnium (Hf) contacts are used as electrodes for hole and electron injection, respectively. However, the large Schottky barrier at the interface of the SWCNTs and the Hf electrode, primarily resulting from the polymer wrapped on the nanotube surface during the sorting process, leads to inefficient electron injection and thus a low electroluminescence efficiency. We find that the efficiency of electron injection can be improved by the local doping of the nanotubes with dielectric layers of YOX-HfO2, which reduces the Schottky barrier at the SWCNT/Hf interface. Accordingly, the (10, 5) SWCNT film-based LED achieves an external quantum efficiency of larger than 0.05% without any optical coupling structure. With further improvement, we expect that such an infrared light source will have great application potential in the carbon nanotube monolithic optoelectronic integrated system and on-chip optical interconnection, especially in the field of short-distance optical fiber communications and data center.

Influence of thermal annealing on silicon negative ion implanted SiO2 thin films

SiO2 thin film of thickness 300 nm grown on p-type silicon substrate was implanted with 100 keV silicon negative ions with fluences varying from 5×1015 to 1×1017 ions cm−2. The implanted samples were annealed at the temperature of 500 °C under N2 ambient. Electron spin resonance (ESR), Fourier transform infrared (FTIR), Photoluminescence (PL), and glancing angle X-ray diffraction (GXRD) techniques have been used to investigate the implanted SiO2 thin film after thermal annealing. ESR studies revealed the absence of vacancy defects after thermal annealing. FTIR studies showed variations in the vibrational modes, attributed to the formation of new structures after annealing at 500 °C. PL studies showed the presence of a peak at 720 nm with an intensity higher than that observed for the unannealed SiO2 samples. This effect showed a decrease in the non-radiative defect centers with an increase in the radiative Si:SiO2 interface states after thermal annealing. The presence of an additional peak at 692 nm may be attributed to the radiative recombination centers associated with silicon nanoclusters formed after annealing at 500 °C. GXRD studies showed a decrease in the intensity of the spectra for the samples implanted with 1×1016 and 5×1016 ions cm−2 after thermal annealing at 500 °C. This result reveals the formation of new SiOx structures in SiO2 thin film.

Systematic improvement of excitonic features in hydrothermally synthesized WS2 due to post-synthesis drying

WS2 nanostructures were produced by mechanically exfoliating bulk WS2 powders synthesized through a solution-based hydrothermal route using WCl6 and thioacetamide (TAA) as reactants. An unoptimized post-synthesis recipe, which constitutes the last step, is the major hindrance in achieving a reproducible and scalable production strategy of layered bulk WS2 crystals. We have reported a comprehensive study on the crystal, morphological, and luminescence properties of WS2 material which have undergone post-synthesis treatment i.e. dried at mild temperature with varied dwelling times. The as-synthesized WS2 material which used to be in distorted 1T metallic phase, due to ionic intercalation released from the organic reactants, was found to evolve crystallographically into a stable 2H semiconducting phase with increased drying temperature and dwelling time. An in-depth optical analysis of the WS2 nanostructures through PL and PLE spectroscopy revealed substantial improvement in the intensity of A and B excitonic features for the sample dried at 80 °C for 24 h, indicating a reduction in the non-radiative defect centers in the sample under the post-synthesis conditions. We believe an effective post-synthesis treatment is needed for semiconducting 2H-WS2 synthesis through the solution route to improve its crystal (i.e. structural) and optical properties for potential electronic applications.

A conjugated Donor-acceptor blend passivation interlayer for the high-performance carbon-based perovskite solar cells

The interfacial properties between perovskite active layer and carbon electrode significantly affects the energy conversion efficiency and stability of carbon-based perovskite solar cells. In this work a conjugated Donor-Acceptor blend with a dendrite shaped copper phthalocyanine derivative 8TPAEPC as a donor (D) and Y6 as a typical acceptor (A) was designed to enhance the carrier extraction across the perovskite/carbon interface. The respective D and A molecules form strong interactions with I− and Pb2+ on the surface of perovskite by rich functional group atoms, which can synergistically passivate the non-radiative defects. Moreover, the dipoles from D-A coupling construct a strong internal built-in electric field for further suppression of the unwanted recomination. Compared with 8TPAEPC, 8TPAEPC-Y6 blend exhibits the faster charge interface transfer dynamics. Consequently, Carbon-based perovskite solar cells (C–PSCs) optimized by 8TPAEPC-Y6 achieve champion power conversion efficiency (PCE) of 17.07%, superior to those with 8TPAEPC (16.08%), Y6 (15.68%) and pristine perovskite (14.06%). Meanwhile, the C–PSCs with the hydrophobic 8TPAEPC-Y6 blend greatly improved moisture long-term stability that over 90% PCE could remain as long as 90 days. This work finds out an innovative D-A blend interfacial solution for achieving highly efficient and stable C–PSCs.

Defect evolution of iodine vacancy and related strain modulation in all-inorganic halide perovskites

Vacancy related defects play a crucial role in optoelectronic properties and carrier transport for photovoltaic materials, especially for its structural evolution becoming non-radiative defects induced by strain. Thus far, the evolution phenomena of vacancy defects in halide perovskite triggered by energy or strain have not been systematically investigated. Herein, we study the change in defect levels occurred in different inorganic perovskite systems and the situation caused by strain in varied strength based on density functional theory calculations. We discover that VI deep levels are easily transformed from shallow levels due to the formation of Pb–Pb dimers and octahedral distortion in all-inorganic perovskites, especially in CsPbI3. Moreover, strain can be quantitatively applied to control the suppression or enhancement of the formation of dimer in CsBI3 (B = Pb/Ge) perovskites. Eventually, our calculation results unravel that the defect physics of VI defect and the formation mechanism of non-radiative center in all inorganic perovskites, which depends on the strain strength and the accompanying octahedral distortion. The strain modulation and its quantitation effect on defect evolution of dominant vacancy map a pioneering route toward fabricating high performance inorganic photovoltaics.

Incorporation of MOF UiO-66-NH2 and polyaniline for enhanced performance of low-cost carbon-based perovskite solar cells

Perovskite solar cells (PSCs) have emerged as a promising technology in recent years. The commercial viability of PSCs is highly anticipated soon. However, the only hindrance is its limited long-term stability due to moisture, humidity, higher working temperatures, and UV-A light deterioration. Consequently, the PSC structure can be modified accordingly. Additive engineering and surface passivation are excellent techniques. In this study, we successfully utilized Polyaniline (PANI) and UiO-66-NH2 metal-organic framework (MOF) to enhance the performance of PSC devices. PANI passivates nonradiative recombination and defects caused by UV-A light at the ETL-perovskite interface. MOF additive is incorporated into the perovskite precursor solution.XRD indicates that MOF enhances its crystallinity and surface morphology. Additionally, perovskite grain size increases (Scherrer equation); thus, the grain boundary defects decrease. Furthermore, both additives help to restrict Pb2+ ions in the perovskite absorber layer. For the champion cell (with both additives), the enhanced optoelectronic performance with PCE of 11.71% is obtained. A decrease in hydrophilicity of the perovskite surface is demonstrated using MOF-treated cells. Moreover, the treated sample exhibits enhanced stability compared to the untreated cell, as demonstrated through stress testing.

Dual facet passivation of silver halometallate for eco-friendly silver bismuth sulfide near IR photodetector

Ternary chalcogenide silver bismuth sulfide nanocrystals (AgBiS2 NCs) have taken great strides in the past few years to emerge as one of the better eco-friendly alternatives to compete with the prevalent toxic semiconductor materials such as lead sulfide quantum dots (PbS QDs) in the near-infrared (NIR) region. Nevertheless, their implementation in photodetectors has been scarce due to high dark current and complicated solid-state ligand exchange fabrication steps involved, resulting in a lower overall detectivity. The performance is further deemed to be stunted due to the difficulty associated with the passivation of the charge-neutral (100) facet of larger AgBiS2 NCs efficiently. In this work, we aimed to develop a mixed ‘halometallate’ ligand approach, wherein we introduce silver bromide (AgBr) as an ancillary ligand to silver iodide (AgI), passivating both (100) and (111) facets of cubic AgBiS2 solids in a facile solution-phase ligand exchange step to obtain highly dispersible colloidal ink. Decreased bond length, bond angle (Br-Ag-Br), and ionic size of [AgBr2-] anion induces less compressive strain compared to [AgI2–], culminating in higher molecular stability on the AgBiS2 surface. This dual passivation reduces the dark current to 6.01 × 10-7 A cm−2 and a high specific detectivity of 1.8 × 1012 Jones at 800 nm is achieved, comparable to ubiquitous PbS QD devices. We also demonstrate diminished in-gap carrier density population, enhanced light detection, and ultrafast microsecond response at higher wavelengths operating under high bias (-1V) photoconductive mode. This study illustrates the role of optimum surface coverage in eliminating the deleterious non-radiative recombination defect centers by introducing additional ligands in solution-processed AgBiS2 NC and the viability of the mixed ligand approach for stable eco-friendly NIR photodetectors.