Enhanced Power Conversion Efficiency Research Articles

Homojunction Perovskite Quantum Dot Solar Cells with over 1µm-Thick Photoactive Layer.

The solution-processed solar cells based on colloidal quantum dots (QDs) reported so far generally suffer from poor thickness tolerance and it is difficult for them to be compatible with large-scale solution printing technology. However, the recently emerged perovskite QDs, with unique high defect tolerance, are particularly well-suited for efficient photovoltaics. Herein, efficient CsPbI3 perovskite QD solar cells are demonstrated first with over 1µm-thick active layer by developing an internal P/N homojunction. Specifically, an organic dopant 2,2'-(perfluoronaphthalene-2,6-diylidene) dimalononitrile (F6TCNNQ) is introduced into CsPbI3 QD arrays to prepare different carrier-type QD arrays. The detailed characterizations reveal successful charge-transfer doping of QDs and carrier-type transformation from n-type to p-type. Subsequently, the P/N homojunction perovskite QD solar cell is assembled using different carrier-type QDs, delivering an enhanced power conversion efficiency of 15.29%. Most importantly, this P/N homojunction strategy realizes remarkable thickness tolerance of QD solar cells, showing a record high efficiency of 12.28% for a 1.2µm-thick QD active-layer and demonstrating great potential for the future printing manufacturing of QDs solar cells.

Er@C82 as a Bifunctional Additive to the Spiro‐OMeTAD Hole Transport Layer for Improving Performance and Stability of Perovskite Solar Cells

Perovskite solar cells (PSCs) based on 2,2′,7,7′‐tetrakis‐(N,N‐di‐p‐methoxyphenylamino)‐9,9′‐spirobifluorene Spiro‐OMeTAD hole transport layer (HTL) have achieved a huge success in power conversion efficiency (PCE), but the required lithium bis(trifluoromethanesulfonyl)imide (Li‐TFSI) dopant in Spiro‐OMeTAD HTL is hygroscopic, not only impairing the charge transport but also inducing the instability of PSCs. Herein, Er@C82, which consists of a hydrophobic fullerene cage encapsulating an Er3+ ion, is first introduced as a novel additive to modify the Li‐TFSI‐based Spiro‐OMeTAD HTL. By adding a tiny amount of Er@C82 (0.09 mg mL−1) in the Spiro‐OMeTAD HTL, the PSC exhibits an efficiency promotion from 17.53% to 19.22%. The PCE enhancement is mainly attributed to the improved film quality of HTL after adding Er@C82, which promotes the oxidation of Spiro‐OMeTAD, resulting in faster hole transport and less charge recombination. Simultaneously, the hydrophobic Er@C82 and the improved film quality of HTL lead to a dramatically enhanced stability of PSCs. Accordingly, the Er@C82‐modified devices can maintain over 70% and 80% of the initial efficiencies after exposure in air for 400 h and in an Ar atmosphere for 2000 h, respectively. Therefore, this bifunctional Er@C82 additive provides a promising pathway for fabricating highly efficient and stable PSCs.

A Cost-Effective Alpha-Fluorinated Bithienyl Benzodithiophene Unit for High-Performance Polymer Donor Material.

To reduce synthetic cost of the classic fluorinated bithienyl benzodithiophene (BDTT-F) unit, here, an alpha-fluorinated bithienyl benzodithiophene unit, namely, α-BDTT-F (F atom in the α position of the lateral thiophene unit), is developed by the isomerization strategy of exchanging the positions of the F atom and flexible alkyl chain on the lateral thiophene unit of the BDTT-F unit. The α-BDTT-F unit was synthesized with less synthetic steps, higher synthetic yield, and less purification times from the same raw materials as those of the BDTT-F unit, thus with low synthetic cost. Theoretical calculation indicates that the α-BDTT-F unit possesses a similar twisted conformation and electronic structures as those of the BDTT-F unit. The α-BDTT-F-based polymer α-PBQ10 exhibits similar light absorption and energy levels as those of the corresponding BDTT-F-based polymer PBQ10 but marginally increased molecular aggregation and stronger hole transport than PBQ10. In consequence, the α-PBQ10:Y6-based polymer solar cell demonstrates a slightly enhanced power conversion efficiency (PCE) of 16.26% compared with that of the PBQ10:Y6-based device (PCE = 16.23%). Also, the PCE is further improved to 16.77% through subtle microscopic morphology regulation of the photoactive layer with the fullerene derivative indene-C60 bisadduct as the third component. This work provides new ideas for the design of low-cost and high-efficiency photovoltaic molecules.

Efficient small-molecule donor with improved structural order and molecular aggregation enabled by side-chain modification

Side-chain modification is a proven effective approach for morphology manipulation in organic solar cells (OSCs). However, in-depth analysis and investigation involving side-chain modification towards morphology improvement, including molecular microstructure, orientating packing and aggregation are urgent for all-small-molecule (ASM) systems. Herein, employing a fluorine-modified two-dimension benzodithiophene (BDT) as central unit, we contrastively synthesized two small-molecule donors, namely BDT-F-SR and BDT-F-R, each welding alkylthio side-chains on thienyl of central BDT unit and the other grafted non-sulfuric alkyl side-chains. As predicted, the synergetic side-chain modification of fluorination and alkyl changeover triggers diverse molecular dipole moments and orientations, resulting in different molecular energy levels, thermal stabilities, molecular planarity and order. Eventually, together with the preeminent small-molecule acceptor Y6, BDT-F-R-based ASM OSCs obtain enhanced power conversion efficiency (PCE) of 13.88% compared to BDT-F-SR-based devices (PCE of 12.75%) with more suitable phase-separation and balanced carrier mobilities. The contrast results reveal that alkyl side-chains seem to be a more satisfactory partner for fluorine-modified 2D BDT-based small-molecule donors compared to alkylthio pendants, and highlight the significance of subtle side-chain modification for molecular structural order fun-tuning and morphology control, laying the foundation for efficient ASM OSCs.

Energy management in hybrid organic-silicon nanostructured solar cells by downshifting using CdZnS/ZnS and CdZnSe/ZnS quantum dots

Management of the solar spectrum by downshifting has been a key theme in broadband solar cell research over the last few years. The absorption of high-energy photons that exceed the bandgap edge of Si causes thermalization of charge carriers, which is a major loss mechanism by which collected energy is underutilized in silicon solar cells. The spectral response of Si also falls in the UV region. Progress in overcoming these effects achieved by modifying the input spectrum will dramatically enhance power conversion efficiency (PCE). Herein we report the application of highly luminescent CdZnS/ZnS and CdZnSe/ZnS quantum dots (QDs) as downshifting materials for nanostructured silicon. The applied QDs show major potential for shifting the high energy in the ultraviolet region to low energy, which is then transferred to the underlying silicon nanostructures via radiative and nonradiative energy transfer. This energy transfer dramatically improves the cell efficiency from 10.4% to 13.5%, showing this approach to be a reliable solution for improving solar cell properties. A Novel hybrid organic/inorganic silicon nanotips solar cell employing CdZnS/ZnS QDs as a downshifting layer which exhibits a drastic enhancement in the cell characteristics due to the radiative and nonradiative energy transfer (RET & NRET) from the QDs to underlying silicon nanostructure. • Highly emissive CdZnS/ZnS and CdZnSe/ZnS core/shell QDs were prepared by hot injection in two growth steps. • Silicon nanowires were fabricated by metal-catalyzed chemical etching and modified to tapered nanotip structure. • The current QDs show high potential for downshifting in hybrid silicon solar cells and improve the PCE to 13.49%.

Organic additives in all-inorganic perovskite solar cells and modules: from moisture endurance to enhanced efficiency and operational stability

Power conversion efficiency (PCE) of perovskite solar cells (PSC) has been skyrocketed to certified 25.5% owing to their improved and tunable optoelectronic properties. Although, various strategies have been adopted to date regarding PCE and stability enhancement within PSC technology, certain instability factors (moisture, heat, light) are hindering their commercial placement. Recently, all-inorganic PSCs got hype in the photovoltaic research community after they attained PCE > 20% and due to their significant endurance against heat and light mishmashes, but there only left moisture sensitivity as the only roadblock for their industrial integration. Here, we review the recent progress of additive inclusion into all-inorganic (CsPbX3) PSCs to stabilize their intrinsic structure and to withstand the performance limiting factors. We start with the detailed description of chemical instability of different perovskite compositions, phase segregation, and how organic molecules and dyes help to repair the structural defects to improve the overall PCE and stability of PSCs. Moisture endurance as a result of chemical passivation through organic additives, low-dimensional inorganic PSCs to enhance device stability and scalable fabrication of CsPbX3 PSCs are also reviewed. The challenges of module degradation and design implications with proposed strategies and outlook are interpreted in the ending phrases of this review.

Over 21% Efficiency Stable 2D Perovskite Solar Cells.

Owing to their insufficient light absorption and charge transport, 2D Ruddlesden-Popper (RP) perovskites show relatively low efficiency. In this work, methylammonium (MA), formamidinum (FA), and FA/MA mixed 2D perovskite solar cells (PSCs) are fabricated. Incorporating FA cations extends the absorption range and enhances the light absorption. Optical spectroscopy shows that FA cations substantially increase the portion of 3D-like phase to 2D phases, and X-ray diffraction (XRD) studies reveal that FA-based 2D perovskite possesses an oblique crystal orientation. Nevertheless, the ultrafast interphase charge transfer results in an extremely long carrier-diffusion length (≈1.98µm). Also, chloride additives effectively suppress the yellow δ-phase formation of pure FA-based 2D PSCs. As a result, both FA/MA mixed and pure FA-based 2D PSCs exhibit a greatly enhanced power conversion efficiency (PCE) over 20%. Specifically, the pure FA-based 2D PSCs achieve a record PCE of 21.07% (certified at 20%), which is the highest efficiency for low-dimensional PSCs (n≤ 10) reported to date. Importantly, the FA-based 2D PSCs retain 97% of their initial efficiency at 85°C persistent heating after 1500h. The results unambiguously demonstrate that pure-FA-based 2D PSCs are promising for achieving comparable efficiency to 3D perovskites, along with a better device stability.

Enhanced efficiency of DSSC by lyophilized tin-doped molybdenum sulfide as counter electrode

The influence of lyophilization on the electrochemical properties of hydrothermally synthesized tin (Sn) doped molybdenum sulfide (MoS2) nanostructures are investigated thoroughly. The lyophilized tin doped MoS2 used as counter electrode (CE) in dye-sensitized solar cells (DSSCs) showed high efficiency and better stability. Power conversion efficiency (PCE) of 7.14% is achieved using lyophilized 2.5% Sn-doped MoS2 as CE in DSSCs, which is much higher than devices made of CE comprising oven air annealed samples (5.74%). The major enhancement of PCE is due to the large surface area of Sn-doped lyophilized MoS2 nanostructures as well as the high electrocatalytic activity of MoS2 towards reduction reaction, which are observed from BET, CV and EIS measurements. Sequential CV scanning further showed the high electrochemical stability of the Sn-doped MoS2 nanostructures. This indicates the useful application of lyophilizer technique to produce various other metal sulfide nanostructures to increase the porosity and overall surface area of the materials for optimum device performance.

Photoanode modification of dye-sensitized solar cells with Ag/AgBr/TiO2 nanocomposite for enhanced cell efficiency

Ag/AgBr compounds are well renowned visible light photosensitizers with inherent stability issues due to decomposition of the halide to metallic silver under illumination. However, when loaded onto a wide bandgap semiconductor with a more positive conduction band (i.e. TiO2) than that of AgBr, they become much more stable after some initial decomposition. Stabilization occurs due to transfer of extra electrons that could combine with interstitial Ag+ to form Ag0 clusters to the wide bandgap semiconductor. Even though Ag/AgBr/TiO2 nanocomposites are widely used in photocatalytic applications, their use in dye-sensitized solar cells have not been reported to date. In this work we incorporated an Ag/AgBr/TiO2 nanocomposite which was successfully synthesized via a one-pot synthesis procedure to DSC active material and obtained an enhanced power conversion efficiency (PCE) of 8.46%. The increase in PCE is an impressive 31% compared to the PCE of 6.45% of the reference cell made with P25 TiO2. The enhanced efficiency can be attributed to the synergistic effects rendered by both AgBr and metallic Ag. AgBr is highly efficient in generating electron – hole pairs under ≈ 470 nm visible light. Plasmonically enhanced effects introduced by Ag nanoparticles further improve the charge generation and separation both in the dye and AgBr. These cumulative effects combined with the stability maintained by the TiO2 matrix of the DSC active material results in an efficiently performing DSC due to the incorporation of Ag/AgBr/TiO2 nanocomposite into the photoanode.

NiOx‐Seeded Self‐Assembled Monolayers as Highly Hole‐Selective Passivating Contacts for Efficient Inverted Perovskite Solar Cells

Self‐assembled monolayers (SAMs) have emerged as effective carrier transport layers in perovskite (PVK) solar cells because of their unique ability to manipulate interfacial property, as well as simple processing and scalable fabrication. However, the defects and pinholes derived from their sensitive adsorption process inevitably deteriorate the final device performance. Herein, a sputtered nickel oxide (NiOx) interlayer is used as a seed layer to promote the adsorption of the [2‐(3,6‐dimethoxy‐9H‐carbazol‐9‐yl)ethyl]phosphonic acid (MeO‐2PACz) SAM on the indium tin oxide (ITO) substrate. The promoted adsorption is attributed to the enhanced tridentate binding between MeO‐2PACz and NiOx relative to the conventional bidentate binding between MeO‐2PACz and ITO. In addition, the NiOx modification can simultaneously improve the passivation ability and hole‐selectivity of the MeO‐2PACz, provide a favorable energy‐level alignment at the ITO/PVK interface, and prevent a direct contact between PVK and ITO. As a consequence, this NiOx‐seeded MeO‐2PACz hole transport layer enables a significantly enhanced power conversion efficiency of 19.9% in comparison with 18.4% of the control device. This work provides an effective strategy to improve the performance of the SAM‐based photoelectric device.

Interface Engineering for All‐Inorganic CsPbIBr2 Perovskite Solar Cells with Enhanced Power Conversion Efficiency over 11%

Perovskite solar cells (PVSCs) receive great attention due to their excellent photovoltaic performance. Recently, all‐inorganic PVSCs have been extensively studied owing to their superior thermal and photo stability. Among them, CsPbIBr2 perovskite stands out due to its superb phase stability in ambient environment. However, the severe energy loss caused by non‐radiative recombination limits its development. Herein, a facile interface engineering method is employed to modify the electron transporting interface and reduce the energy loss. The insertion of a thin polyethylenimine ethoxylated (PEIE) film between SnO2 and the perovskite can simultaneously tune the work function of SnO2 and passivate the defects of the perovskite by the amino group in PEIE. Meanwhile, the PEIE interface serves as a modifier to enhance the crystallinity of the perovskite film, leading to enlarged grain size and reduced grain boundaries. As a result, the power conversion efficiency was enhanced from 8.7% for the SnO2‐based device to 11.2% for the SnO2/PEIE‐based device, with an open‐circuit voltage of 1.29 V, a short‐circuit current of 11.0 mA/cm2, and a fill factor of 78.6%. Moreover, the photostability of devices were improved, which retained over 80% of its initial efficiency under continuous one sun illumination for 500 h. This work proves the effectiveness of interface engineering to boost the efficiency and stability of all‐inorganic PVSCs.

A Thienothiophene‐Based Cation Treatment Allows Semitransparent Perovskite Solar Cells with Improved Efficiency and Stability (Adv. Funct. Mater. 42/2021)

Thienothiophene-Based Cation Treatment In article number 2103130, Selcuk Yerci, Gorkem Gunbas, and co-workers fabricate perovskite solar cells (PSC) by treating 3D perovskite surfaces with a novel cation, which enables higher power conversion efficiency (PCE) and improved stability. The PCE enhancement is explained by drift diffusion modeling. Additionally, treated 3D perovskite based semitransparent PSCs are realized with increased stability and with one of the highest reported efficiencies for double cationic 3D perovskites.

Recent progress of efficient flexible solar cells based on nanostructures

Flexible solar cells are important photovoltaics (PV) technologies due to the reduced processing temperature, less material consumption and mechanical flexibility, thus they have promising applications for portable devices and building-integrated applications. However, the efficient harvesting of photons is the core hindrance towards efficient, flexible PV. Light management by nanostructures and nanomaterials has opened new pathways for sufficient solar energy harvesting. Nanostructures on top surfaces provide an efficient pathway for the propagation of light. Aside from suppressing incident light reflection, micro-structured back-reflectors reduce transmission via multiple reflections. Nanostructures themselves can be the absorber layer. Photovoltaics based on high-crystallinity nanostructured light absorbers demonstrate enhanced power conversion efficiency (PCE) and excellent mechanical flexibility. To acquire a deep understanding of the impacts of nanostructures, herein, a concise overview of the recent development in the design and application of nanostructures and nanomaterials for photovoltaics is summarized.

Omnidirectional light absorption enhancement of perovskite solar cells by an antireflection film with holographic lithography microstructures.

We report an omnidirectional light absorption enhancement of a perovskite solar cell (PSC) using antireflection (AR) film with soft imprinted microstructures from master molds via holographic lithography technology, which has high throughput and repeatability. The PSC's omnidirectional power conversion efficiency (PCE) enhancement is achieved by reducing Fresnel surface reflections and enhancing the optical path length. The maximum PCE of PSCs with AR film is up to 20.27%, corresponding to an absolute increase of 0.93% compared to 19.34% of control devices. Significantly, the enhancements of PCE increase with incident angle enlargement, which attributes to more effective Fresnel surface reflection suppression. Moreover, AR films exhibit water and dust repellent properties due to hydrophobicity, which is beneficial for PSC's long-term stability and light harvesting.

QSPR modeling of absorption maxima of dyes used in dye sensitized solar cells (DSSCs)

Dye-sensitized solar cells (DSSCs) have recently received a significant attention as possible sources of renewable energy. As a result, a significant effort is being made to develop organic dyes for highly power conversion efficient DSSCs, in order to overcome the disadvantages of previous solar cell systems, such as cost reduction, weight reduction, and production methods that minimize environmental pollution. As shown by multiple recent research publications, computational techniques such as quantitative structure–property relationship (QSPR) modeling may aid in the development of suitable dyes for DSSCs satisfying many fundamental desired characteristics. The current report provides robust, externally verified QSPR models for five chemical classes of organic dyes (Triphenylamines, Phenothiazines, Indolines, Porphyrins and Coumarins) based on experimentally determined absorption maxima values. The size of the dye data points utilized to develop the models is the largest known to date. The QSPR models were constructed using only two-dimensional descriptors with clear physicochemical meaning. Using the best subset selection approach, we built 5, 3, 4, 3 and 2 descriptor models for the Triphenylamine, Phenothiazine, Indoline, Porphyrin and Coumarin classes, respectively. The models were validated both internally and externally, and then consensus predictions were made for specific categories of dyes using the developed partial least squares (PLS) models, and the “Intelligent consensus predictor” tool (http://teqip.jdvu.ac.in/QSAR_Tools/) was used to determine whether the quality of test set compound predictions can be improved through the “intelligent” selection of multiple PLS models. We identified from the insights gained from the developed models several chemical attributes that are important in enhancing the absorption maxima. Thus, our study may be utilized to predict the λmax values of novel or untested organic dyes and to give insights that will aid in the development of new dyes for use in solar cells with increased λmax values and enhanced power conversion efficiency.

Improved open-circuit voltage of CsPbI3 quantum dot solar cells by PMMA interlayer

All-inorganic CsPbI3 quantum dots perovskite solar cells (QDPSCs) have wide potential application due to their excellent photoelectric properties with high environmental stability. However, the poor interface contact between the light absorption layer and hole transport layer (HTL) results in the serious carrier recombination and the large open-circuit voltage (VOC) loss. Herein, we introduce the insulating PMMA (poly(methyl methacrylate)) buffer layer into CsPbI3 quantum dots (QDs)/Cu12Sb4S13 QDs HTL interface in all-inorganic QDPSCs with the structure of FTO/c-TiO2/m-TiO2/CsPbI3 QDs/Cu12Sb4S13 QDs/Au. The interface carrier recombination is obviously suppressed and the significant VOC improvement from 1.04 V to 1.14 V is obtained with the incorporated PMMA buffer layer. The devices with PMMA buffer layer show the enhanced power conversion efficiency (PCE) of 10.99%, and the improvement of 9.71% is achieved compared to that of the control devices (10.02%). The stability is significantly enhanced due to the intrinsic hydrophobic characteristic of PMMA, and the devices retain 62.69% of their initial PCE after stored in air condition for 15 days, which is greatly improved compared with the control device without PMMA.

Efficient and Stable FAPbBr3 Perovskite Solar Cells via Interface Modification by a Low-Dimensional Perovskite Layer

Lead bromide perovskite with high bandgap and good stability has aroused broad interest for utilization in perovskite solar cells (PSCs) with high photovoltage, especially as a candidate for the front cell of tandem solar cells. However, the efficiency of lead bromide PSCs is still much lower than the standard lead iodide PSCs, and the defects in the perovskite are one of the main limiting factors hindering device performance. The construction of a 2D/3D perovskite interface is an effective way to passivate the interfacial defects and achieve efficient and stable PSCs. Herein, a facile and effective phenethylammonium bromide (PEABr) treatment method was applied to build a 2D/3D perovskite interface in FAPbBr3 solar cells. An ultrathin layer of 2D PEA2PbBr4 perovskite was successfully fabricated on the surface of 3D FAPbBr3 perovskite by depositing the PEABr solution on the 3D perovskite films. The 2D perovskite layer significantly passivated the interfacial defects, leading to enhancement of power conversion efficiency from 7.7% to 9.4% and fill factor from 67.6% to 77.6%. Moreover, the hydrophobic alkyl chain in the PEA cation improved the moisture tolerance of the perovskite and significantly increases the solar cell stability. Additionally, the PEABr treatment strategy was successfully utilized for preparing semitransparent 2D/3D FAPbBr3 perovskite solar cells.

3‐D Modeling of Ultrathin Solar Cells with Nanostructured Dielectric Passivation: Case Study of Chalcogenide Solar Cells

AbstractUltrathin solar cells can be a path forward to low‐cost photovoltaics due to their reduced material consumption and shorter required deposition times. With excellent surface passivation, such devices may feature higher open‐circuit voltages (VOC). However, their short‐circuit current density (JSC) may be reduced due to decreased light absorption. This mandates implementation of efficient light‐trapping structures. To design efficient ultrathin solar cells that combine surface‐passivation and light‐trapping features, accurate 3‐D modeling is necessary. To this end, a novel 3‐D optoelectrical finite‐element model is developed to analyze the performance of ultrathin solar cells. The model is applied to the case of ultrathin (<500 nm) chalcogenide solar cells (copper indium gallium (di) selenide, CIGSe), rear‐passivated with nanostructured Al2O3 to circumvent optical and electrical losses. It is found that such a nanopatterned dielectric passivation scheme enhances broadband light‐trapping with reduced rear‐surface recombination, resulting in an absolute power conversion efficiency enhancement of 3.9%, compared to cells without passivation structure. Overall, the work shows how 3‐D finite element modeling can aid in analyzing and developing new optical and electrical solar cell designs for ultrathin solar cells such as those based on chalcogenides and perovskites.

Enhanced power conversion efficiency of the polycrystalline solar cells using spinel MnFe2O4 nanoparticles as an ARC material

The Spinel magnetic nanoparticles (MnFe2O4) were prepared by using the precursors Manganese Chloride (Mncl2) and Ferric Chloride (FeCl2) using co-precipitation method. The synthesized nanoparticles can be used as a suitable Antireflective coating (ARC) for increasing the power conversion efficiency (PCE) of silicon solar cells. The prepared nanoparticles are deposited on the silicon solar cells using spin coating method. Single to quadruple layers of MnFe2O4 were coated. The prepared nanoparticles were confirmed by using characterization such as X-ray Diffraction (XRD), Fourier-Transform Infrared Spectroscopy (FTIR), Atomic Force Microscopy (AFM), Field Emission Scanning Electron Microscope (FESEM) and Energy Dispersive Spectroscopy (EDX). The XRD analysis reveals the formation of the spinel nanostructure for the synthesized MnFe2O4 nanoparticles. EDX analysis was used to check the elemental composition of the Mn, Fe and O in the samples. The crystal structure, particle size and lattice parameters were obtained by the XRD technique. The optical and electrical characterizations were done comprehensively to find out the performance of coated and uncoated solar cells. The surface morphology and the coating thickness were measured using the AFM technique.

Raman enhancement mechanism and experiments of cavity-enhanced AgNP decorated tapered fiber sensor.

A Raman sensor based on a cavity-enhanced Ag nanoparticle (AgNP) decorated tapered fiber is proposed. Its Raman enhancements are mainly caused by the localized surface plasmon resonance effect of AgNPs decorated on the tapered optical fiber surface and the further reflective laser excitation induced by the capillary-based reflective cavity. We theoretically investigate the backward Stokes power conversion efficiency and cavity enhancement factor of the sensor. The calculated relationship between the cavity enhancement factor ξ and distance L from the tip to reflective rod is also discussed. Subsequently, the proving experiments were carried out for a tapered fiber surface-enhanced Raman scattering (SERS) probe and cavity-enhanced metal decorated tapered fiber Raman sensors. The analytical enhancement factor is 5.51×104 for the tapered fiber SERS probe. Moreover, the predicted curves of the theoretical model are close to the experimental values. This Letter provides a possible way to rigorously quantify the complete coupling efficiency for tapered fiber SERS probes, as well as cavity enhancement factors of cavity-enhanced Raman sensors.