Power Conversion Efficiency Of Perovskite Solar Cells Research Articles

Enhancing the photovoltaic performance of perovskite solar cells by potassium ions doping

Organometal halide perovskite solar cells (PSCs) have attracted much attention due to their high photovoltaic efficiency and low fabrication cost. The perovskite layer plays a critical role on the power conversion efficiency (PCE). The main issues in perovskite layer are the coverage and crystallinity of perovskite grain based on substrate. Here, potassium ions were doped into perovskite layer to improve the growth, structure, properties of perovskite films and the photovoltaic performance of PSCs. The potassium ions significantly affect the Jsc and efficiency but affect the Voc slightly. The Jsc increases from 14.73 to 19.98 mA cm−2, and the efficiency increases from 10.16 to 13.57% at the doping level of 0.5% (molar ratio). The incorporation of potassium ions into perovskite also affects the crystallisation and morphology of the perovskite films and thus the PCE of PSCs. The crystallinity and denseness of perovskite film are enhanced and crystallite size is enlarged after potassium ions are doped into perovskite layer. At the same time, hysteresis free and stable device is obtained with the PSC at the doping level of 0.5% of potassium ions (molar ratio).

Improving Electron Extraction Ability and Device Stability of Perovskite Solar Cells Using a Compatible PCBM/AZO Electron Transporting Bilayer.

Due to the low temperature fabrication process and reduced hysteresis effect, inverted p-i-n structured perovskite solar cells (PSCs) with the PEDOT:PSS as the hole transporting layer and PCBM as the electron transporting layer have attracted considerable attention. However, the energy barrier at the interface between the PCBM layer and the metal electrode, which is due to an energy level mismatch, limits the electron extraction ability. In this work, an inorganic aluminum-doped zinc oxide (AZO) interlayer is inserted between the PCBM layer and the metal electrode so that electrons can be collected efficiently by the electrode. It is shown that with the help of the PCBM/AZO bilayer, the power conversion efficiency of PSCs is significantly improved, with negligible hysteresis and improved device stability. The UPS measurement shows that the AZO interlayer can effectively decrease the energy offset between PCBM and the metal electrode. The steady state photoluminescence, time-resolved photoluminescence, transient photocurrent, and transient photovoltage measurements show that the PSCs with the AZO interlayer have a longer radiative carrier recombination lifetime and more efficient charge extraction efficiency. Moreover, the introduction of the AZO interlayer could protect the underlying perovskite, and thus, greatly improve device stability.

(Invited) Operando Characterization of Energy Conversion and Storage Devices Using Scanning Probe Microscopy

Energy conversion/storage devices, such as solar cells (SCs) and lithium ion batteries (LIBs), have been actively researched along with the growing interest in energy and environment issues. In order to further improve the performance of these devices, it is essential to have a deeper understanding of their working principles. To achieve this, the characterization of their physical and chemical properties under device operation conditions, so-called operando measurement, is thought to be highly effective. For example, in the case of SCs, important information related with photovoltaic conversion processes can be obtained by measuring the electrical potential, electronic states, and charge distribution in the vicinity of the excitation center under light irradiation conditions. In the case of LIBs, characterization of electrical potential and lithium ion distribution in the electrodes and electrode-electrolyte interfaces during charging and discharging processes is expected to provide strong insight into the origin of interface resistance and mechanism of cell degradation. Up to date, X-ray and electron spectroscopy techniques have led the field of operando measurement. However, the spatial resolution of those techniques is insufficient to characterize next generation devices that actively utilize nanostructure. Thus, in our group, as an operando measurement technique to evaluate the local properties at nanoscale and even down to the atomic scale, we have been working on developing scanning probe microscopy (SPM) systems that operate under various environments (under light irradiation, voltage application, inert atmospheric conditions). In this talk, we will introduce recent our works related to the characterization of perovskite SCs and all-solid-state LIBs by operando nano-scale profiling of electrical potential distribution using Kelvin probe force microscopy (KPFM). Perovskite solar cells (PSCs) have attracted great research interest owing to their advantages in high power conversion efficiency and low-cost fabrication. Although the power conversion efficiency of PSCs is very high (record is 22.7 %), the detailed photovoltaic conversion processes has not well understood yet compared with the conventional inorganic SCs. In this work, we used KPFM to measure internal electrical potential distribution of PSCs during device operation. We observed that the change of electrical potential induced by illumination occurred strongly at the interface between the perovskite film and charge transport layers, which suggests that charge separation mainly occurred at those interfaces, not in the perovskite film. Also, we found that the position of charge separation varied depending on the composition of perovskite materials and the device structure. These findings will be helpful for understanding the fundamental mechanism within PSCs and achieving high device efficiency. All-solid-state (ASS) LIBs are a promising candidate for next-generation energy storage devices. However, solid electrolytes for the current ASS-LIBs have various disadvantages, such as low power densities caused by high ionic resistivity at the interfaces between active materials and solid electrolytes. The high ionic resistivity has been attributed to the Li depleted layer or defects at the interfacial layer. For the fundamental understanding of the origin of interfacial resistivity, novel in situ techniques for measuring the distribution of the internal potential and/or Li ion concentration of LIB cells are strongly required. In this work, we combined Ar ion milling under non-atmospheric conditions with cross-sectional KPFM for direct imaging of the internal electrical potential distribution of the ASS-LIBs. We succeeded in the direct visualization of the change in the potential distribution of the cathode composite electrode arising from the battery charging (electrochemical reaction). The results obtained provided several insights into the battery operation, such as the behavior of Li ions and inhomogeneity of electrochemical reactions in the electrode.

New down-converter for UV-stable perovskite solar cells: Phosphor-in-glass

Degradation of hybrid lead halide perovskite by UV light is a crucial issue that limits the commercialization of lead halide perovskite solar cells (PSCs). To address this problem, phosphor-in-glass (PiG) is used to convert UV to visible light. Down-conversion of UV light by PiG dramatically increases UV-stability of PSCs and enables PSCs to harvest UV light that is currently wasted. Performance of PSCs with PiG layer does not change significantly during 100 h-long UV-irradiation, while conventional PSCs degrade quickly by 1 h-long UV-irradiation. After 100 h long UV-irradiation, power conversion efficiency of PSCs with PiG is 440% larger than that of conventional PSCs. This result points a direction toward PSCs which are very stable and highly efficient under UV light.

Morphology and Optoelectronic Variations Underlying the Nature of the Electron Transport Layer in Perovskite Solar Cells

Perovskites based on methylammonium lead halides, CH3NH3PbX3 (X = Cl, Br, I), have emerged as one of the most promising materials in solar cell technology. Although the photovoltaics field has witnessed significant progress in the power conversion efficiency (PCE) of perovskite solar cells, unveiling the contribution of the various factors (i.e., energy level alignment, trap states, electron (hole) mobility, interface interactions, and morphology) affecting the observed PCEs is extremely crucial to achieve reproducible and stable devices. This work aims to understand charge transport and recombination within conventional perovskite solar cells due to modifications of the morphology, optoelectronic properties, and energy levels of the titania electron transport layer. Here, we utilize two different processing methods (i.e., solution and sputtering depositions) to yield three morphologically different titania electron transport layers (i.e., planar bulk TiO2, mesoporous TiOx, and sputtered TiO2). We find that the most important factors affecting the PCEs in perovskite solar cells are related to trap-assisted recombination and energy level alignment due to variations in the electron transport layer/perovskite interface. Similarly, we observe that morphologies of both the electron transport layer and the perovskite active layer play a minor role on the observed PCEs.

Effect of ZrO2 film thickness on the photoelectric properties of mixed-cation perovskite solar cells

In this work, perovskite solar cells (PSCs) were fabricated in the ambient air, with a scaffold layer composed of TiO2/ZrO2 double layer as the mesoscopic layer and carbon as the counter electrode. The effect of ZrO2 thin film thickness on the photovoltaic performances of PSCs was also studied in detail. Results showed that the photoelectric properties of as-prepared PSCs largely depend on the thin film thickness due to a series of factors, including surface roughness, charge transport resistance, and electron-hole recombination rate. The power conversion efficiency of PSCs increased from 8.37% to 11.33% by varying the thin film thickness from 75 nm to 305 nm, and the optimal power conversion efficiency was realized up to the 11.33% with a thin film thickness of 167 nm. This research demonstrates a promising route for the high-efficiency and low-cost photovoltaic technology.

Improvement of current characteristic of perovskite solar cells using dodecanedioic acid modified TiO2 electron transporting layer

In the classical planar heterojunction perovskite solar cells (PSCs), the electron conducting TiO2 layer shows lower conductivity than the hole transporting materials such as spiro-OMeTAD, which becomes one of the key problems in improving the power conversion efficiency (PCE) of PSCs. In this study, the surface of compact TiO2 layer is modified by a thin self-assembled dodecanedioic acid (DDDA) molecular layer. The TiO2 substrates are immersed into the DDDA solution for 0.5, 2.5, 4.5, 22 h, respectively. It is found that the PCE of PSCs is improved when using the DDDA modified TiO2, showing optimized PCE of 15.35%0.75% under AM 1.5G illumination at 100 mWcm-2 after 4.5 h modification. The short current density (JSC) of the best device is improved from 20.34 mA cm-2 to 23.28 mA cm-2, with the PCE increasing from 14.17% to 15.92%. And it is found that the hysteresis of the PSC is also reduced remarkably with hysteresis index decreasing from 0.4288 to 0.2430. In the meantime, the device with DDDA modification shows a significant improvement in light stability, keeping 71% of its initial PCE value after 720 min exposure under AM 1.5G illumination at 100 mW cm-2 without encapsulation. As a contrast, the device without DDDA modification keeps 59% of its initial PCE value under the same condition. To reveal the mechanism, we investigate the surface energy level change using ultraviolet photoemission spectroscopy. It is found that after DDDA modification, the valence-band maximum energy (EVBM) of TiO2 decreases from -7.25 eV to -7.32 eV, and the conduction-band minimum energy (ECBM) of TiO2 from -4.05 eV to -4.12 eV. The shifting of energy level optimizes the energy level alignment at the interface between the TiO2 and perovskite. It promotes the transport of electrons from perovskite layer to compact TiO2 layer and obstructs the transport of holes from perovskite layer to compact TiO2 layer more effectively. In addition, the decrease of ECBM implies the increase of conductivity of TiO2. We further design a series of electrical experiments, and confirm that the modification improves the conductivity of TiO2 obviously with both contact resistance and thin-film resistance decreasing. In summary, our results indicate the enormous potential of the compact TiO2 layer with a thin self-assembled DDDA molecular layer modification to construct efficient and stable planar heterojunction PSCs for practical applications.

Influence of annealing temperature on properties of Cu2O thin films deposited by electron beam evaporation

Inorganic-organic metal halide perovskite solar cells (PSCs) have drawn tremendous attention as a promising next-generation solar-cell technology because of their high efficiencies and low production cost. Since the first report in 2009, the recorded power conversion efficiency (PCE) of PSCs has rapidly risen to 22.1% by using 2, 2', 7, 7'-tetrakis (N,Ndi-p-methoxyphenyl-amine) 9,9-spirobifluorene (spiro-MeoTAD) as hole transport material (HTM), with the efforts devoted to the device architecture optimization, material compositional engineer and interface engineering. Nevertheless, the synthesis and cost of the organic HTM (OHTM) become a major challenging issue and therefore alternative materials are required. In the past few years, the applications of inorganic HTMs (IHTMs) in PSCs have shown large improvement in PCE and stability. For example, PSCs with CuOx as IHTM reached a PCE of 19.0% with better stability. Even more exciting, the theoretical PCE of PSC based on Cu2O HTM reaches 24.4%. So, Cu2O is a promising IHTM for future optimized PSC and the large area uniform preparation is very important. In this paper, Cu2O films have been successfully prepared using electron beam evaporation followed by air annealing. The influences of annealing temperature and time on the composition, structure, and photoelectric characteristics of film are investigated in detail. It is found that the as-deposited film is a mixture of Cu2O and Cu. With the increase of annealing temperature, material composition is transformed from mixture to pure Cu2O phase, and then to CuO, due to the oxidation in air. In an annealing temperature between 100℃ to 150℃, pure Cu2O film can be obtained with an average transmission rate over 70%, optical band-gap of 2.5 eV, HOMO level of -5.32 eV, and a carrier mobility of 30 cm2·V-1·s-1. When the film is treated with a UV lamp, the structure and composition of the film can be changed more easily because of the enhancement of oxidation. Finally, reverted planar PSCs with the structure of Ag/PCBM/CH3NH3PbI3/HTMs/ITO are constructed and compared carefully based on HTMs of Cu2O, with poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate)(PEDOT:PSS), and Cu2O/PEDOT:PSS layers, respectively. An optimum thickness of 40 nm of Cu2O HTM is achieved with high carrier extraction rate. However, the performances of all of the PSCs are inferior to those of PEDOT:PSS-based devices, due to the formation of pinholesin absorber layer resulting from the strong hydrophobicity of Cu2O film. However, the efficiency of PSC based on Cu2O/PEDOT:PSS double-HTM is deteriorated because of the chemical interaction between PEDOT:PSS and Cu2O. These findings provide some important guidelines for the design of HTMs.

Anti-solvent surface engineering via diethyl ether to enhance the photovoltaic conversion efficiency of perovskite solar cells to 18.76%

A quick and repeatable fabrication of compact CH3NH3PbI3 film was achieved by the anti-solvent method which consists of the one-step deposition to the CH3NH3PbI3 film and quickly exposition to the anti-solvent of diethyl ether. The morphology, crystalline quality and properties of the CH3NH3PbI3 film were found to be extraordinary influenced by the adding amount of diethyl ether. Accordingly, the native relationship between the crystal quality of perovskite films and solar cells was revealed. The CH3NH3PbI3 film by adding optimized 600 μL diethyl ether delivered the best power conversion efficiency (PCE) of 18.76% and average PCE of 18.41% with remarkable reproducibility. These results provide an approach to fabricate the high-quality perovskite film and encourage the researchers to further improve the PCE of perovskite solar cells from the aspect of the fabrication process.

Perovskite Solar Cells with ZnO Electron-Transporting Materials.

Perovskite solar cells (PSCs) have developed rapidly over the past few years, and the power conversion efficiency of PSCs has exceeded 20%. Such high performance can be attributed to the unique properties of perovskite materials, such as high absorption over the visible range and long diffusion length. Due to the different diffusion lengths of holes and electrons, electron transporting materials (ETMs) used in PSCs play a critical role in PSCs performance. As an alternative to TiO2 ETM, ZnO materials have similar physical properties to TiO2 but with much higher electron mobility. In addition, there are many simple and facile methods to fabricate ZnO nanomaterials with low cost and energy consumption. This review focuses on recent developments in the use of ZnO ETM for PSCs. The fabrication methods of ZnO materials are briefly introduced. The influence of different ZnO ETMs on performance of PSCs is then reviewed. The limitations of ZnO ETM-based PSCs and some solutions to these challenges are also discussed. The review provides a systematic and comprehensive understanding of the influence of different ZnO ETMs on PSCs performance and potentially motivates further development of PSCs by extending the knowledge of ZnO-based PSCs to TiO2 -based PSCs.

Reduction of Oxygen Vacancy Related Traps in TiO2 and the Impacts on Hybrid Perovskite Solar Cells

One major problem in the application of TiO2 and other oxides as an electron transport layer and optical window in perovskite solar cells (PSCs) is the nonstoichiometric defects related to oxygen vacancies. We report the studies of a TiO2 compact layer annealed in ambient air and in an oxygen environment, and the consequences on planar PSC performance. Chemical analysis and optical studies indicate that oxygen vacancy density can be significantly reduced by changing annealing conditions, leading to higher optical transmission of the TiO2 layer and retarded carrier recombination in the PSC. The carrier dynamics studies found that the electron recombination lifetime was significantly increased. With an improved electron transport layer, the power conversion efficiency of PSCs with a TiO2 compact layer annealed in oxygen was increased from 13.58% to 15.85%, due to a largely enhanced current density when compared to the control PSCs with TiO2 annealed in ambient air.

Facile preparation and characterization of ZnCdS nanocrystals for interfacial applications in photovoltaic devices

Recently, ZnCdS nanocrystals (NCs) have attracted intense attention because of their specific optical properties and electrical characteristics. In this paper, a green and facile solution method is reported for the preparation of ZnCdS nanocrystals using dimethylsulfoxide as small molecular ligands. The ZnCdS nanocrystals are used as an interface modification material in the photovoltaic devices. It is found that the modification of ZnCdS on TiO2 surface not only suppresses the recombination loss of carriers but also reduces the series resistance of TiO2/active layer. Consequently, both of the short circuit current (Jsc) and the fill factor (FF) of the solar cells were significantly improved. Power conversion efficiency (PCE) of 7.75% based on TiO2/ZnCdS was achieved in contrast to 6.65% of the reference devices based on pure TiO2 film in organic solar cells. Furthermore, the PCE of perovskite solar cells based on TiO2/ZnCdS was observed with 8.3% enhancement compared to that of pure TiO2-based ones.

New Efficient 1,1′‐Bi‐2‐naphthylamine‐Based Hole‐Transporting Materials for Perovskite Solar Cells

AbstractTwo new efficient hole transporting materials (HTMs) Q216 and Q219 based on C2‐symmetric 1,1′‐bi‐2‐naphthylamine central core have been synthesized. The bis(4‐methoxyphenyl)amine‐substituted 9H‐carbazole were chose as end groups to link with the central core. The two HTMs have suitable molecular orbital energy levels, being well matched with that of CH3NH3PbI3 and carbon counter electrode. By introducing bis(4‐methoxyphenyl)amine unit (BMPA) to “3” position in carbazole donor, Q219 exhibits smaller dihedral angle between carbazole and naphthyl unit than Q216 with “2”‐BMPA, which may improve the electron donor ability of carbazole and favors to charge transport. The highest power conversion efficiency of PSC based‐Q219 is 9.31 %. EIS and IMVS measurements confirm that Q219 reduces charge recombination in perovskite solar cells (PSCs). Accordingly, the PSC with Q219 favors a 99 mV higher open circuit voltage than that of the Q216. The results provide some useful ideas to further design more promising structure of HTMs.

Dual function of a high-contrast hydrophobic–hydrophilic coating for enhanced stability of perovskite solar cells in extremely humid environments

In spite of a continuous increase in their power conversion efficiency (PCE) and an economically viable fabrication process, organic–inorganic perovskite solar cells (PSCs) pose a significant problem when used in practical applications: They show fast degradation of the PCE when exposed to very humid environments. In this study, the stability of PSCs under very humid conditions is greatly enhanced by coating the surface of the PSC devices with a multi-layer film consisting of ultrahydrophobic and relatively hydrophilic layers. A hydrophobic composite of poly(methyl methacrylate) (PMMA), polyurethane (PU), and SiO2 nanoparticles successfully retards the water molecules from very humid surroundings. Also, the hydrophilic layer with moderately PMMA captures the residual moisture within the perovskite layer; subsequently, the perovskite layer recovers. This dual function of the coating film keeps the PCE of PSCs at 17.3% for 180 min when exposed to over 95% humidity.

Large-area thin film deposition technologies for fabricating hybrid perovskite solar cells

Organic-inorganic hybrid perovskite solar cells have attracted tremendous research interests due to their amazing light to electric power conversion efficiencies (PCEs). In the past four years, the PCE of perovskite solar cells has significantly increased up to 22.1%, which outperforms several other types of third-generation solar cells and becomes the most promising candidate to compete with the traditional silicon-based solar cells. This result is mainly owing to some excellent properties of the hybrid perovskite active layer, such as a high absorption coefficient, an appropriate band gap and a long carrier diffusion length. Nevertheless, most of the reported high efficiencies were only achieved with very small active areas in the range of 0.03 to 0.2cm2, which is likely to cause measurement errors. What is worse, the material utilization ratio is only 1% during film deposition, hindering the industrial production of perovskite solar cells in the future. Therefore, a large-scale production process has become a big challenge to realize the purpose of commercial applications. To date, the best certified PCE of 19.6% has been obtained with an active area exceeding 1cm2. The most important aspect is fabricating large-area uniform, pinhole-free and large crystal grain perovskite thin films for scaling up high PCE perovskite solar cells. To realize the purpose of large-area, high-quality perovskite film fabrication, a range of thin film fabrication techniques have been proposed, including spin-coating, vacuum flash-assisted solution process (VASP), doctor blading, slot-die coating, inkjet printing, spray coating, vapor assisted deposition and soft-cover deposition. This review aims at giving an overview of these thin film deposition techniques for the processing of perovskite thin film fabrication. By comparing the film quality and material utilization ratio corresponding to different film deposition methods, the studies on perovskite thin film fabrication techniques are summarized. Among these techniques, spin-coating has been widely used in laboratory for perovskite film fabrication, but the material utilization ratio is usually less than 1%, hindering the fabrication of perovskite film with large-area. Spin-coating combined with VASP exhibits an amazing result for high-quality perovskite film fabrication, but it still has a low material utilization ratio in spin-coating process. Other techniques, like doctor blading, slot-die coating and inkjet printing are suitable for large-area perovskite film fabrication with high material utilization ratio. Spray coating and soft-cover deposition also have shown great potential for large-area perovskite film fabrication. The PCEs of perovskite solar cells have reached 13% and 17% with an active area exceeding 1cm2, respectively. Particularly, a high-quality perovskite film with a large-area of 51cm2 was obtained by soft-cover deposition, which made this technique more promising for the development of perovskite solar cells in the future. Based on this review, we suggest that VASP is a suitable technique for depositing high-quality large-area perovskite film. It would be a promising technique to combine VSAP with other techniques, such as doctor blading, inkjet printing, etc., to enhance material utilization ratio for large-scale perovskite solar cells. In addition, some simpler and lower-cost techniques should be developed for the fabrication of perovskite solar cells in the future.

Organic-inorganic halide perovskite solar cell with CH3NH3PbI2Br as hole conductor

Perovskite solar cells (PSCs) have attracted enormous interest as the most remarkably growing photovoltaic devices. With the power conversion efficiencies of PSCs excessing 20%, great challenges have been focused on the issues of cost and long-term stability which are majorly related to the hole transport materials. In contrast, the PSCs without special hole conductors show great potential for commercial applications due to their cost-effective and fairly stable features. However, the inferior charge separation at the CH3NH3PbI3 (MAPbI3) and back electrode interface limits the cells for high efficiency. Our strategy is to arrange suitable energy band alignment at the interface to enhance the charge separation. We herein report a MAPbI3/MAPbI2Br cascade structured PSC with MAPbI2Br majorly acting as a hole conductor. The conversion efficiency of the PSCs is greatly improved and a high efficiency of 15.83% is achieved. This new design of using organic-inorganic halide perovskites as hole conductors provides an efficient approach for improving the performance of low-cost PSCs.

Moderately reduced graphene oxide/PEDOT:PSS as hole transport layer to fabricate efficient perovskite hybrid solar cells

Graphene oxide (GO) with single layer was moderately reduced at 200 °C for 4 h under N2. Then the moderately reduced graphene oxide (rGO) water solution was employed as an additive to tune the properties of conventional poly(ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) solution. It's found that the incorporation of rGO into PEDOT:PSS nearly did not change its transparency, hydrophilic property, or the surface roughness. So, the rGO/PEDOT:PSS composite was used as a hole transport layer (HTL) to fabricate perovskite solar cells (PSCs). As a result, PSCs with rGO/PEDOT:PSS as HTL exhibit improved power conversion efficiency than that of PSCs with PEDOT:PSS as HTL. Our findings show that moderately reduced rGO/PEDOT:PSS could be an efficient HTL to improve power conversion efficiency of PSCs.

Highly Efficient LiYF4:Yb(3+), Er(3+) Upconversion Single Crystal under Solar Cell Spectrum Excitation and Photovoltaic Application.

Luminescent upconversion is a promising way to harvest near-infrared (NIR) sunlight and transforms it into visible light that can be directly absorbed by active materials of solar cells and improve their power conversion efficiency (PCE). However, it is still a great challenge to effectively improve the PCE of solar cells with the assistance of upconversion. In this work, we demonstrate the application of the transparent LiYF4:Yb(3+), Er(3+) single crystal as an independent luminescent upconverter to improve the PCE of perovskite solar cells. The LiYF4:Yb(3+), Er(3+) single crystal is prepared by an improved Bridgman method, and its internal quantum efficiency approached to 5.72% under 6.2 W cm(-2) 980 nm excitation. The power-dependent upconversion luminescence indicated that under the excitation of simulated sunlight the (4)F(9/2)-(4)I(15/2) red emission originally results from the cooperation of a 1540 nm photon and a 980 nm photon. Furthermore, when the single crystal is placed in front of the perovskite solar cells, the PCE is enhanced by 7.9% under the irradiation of simulated sunlight by 7-8 solar constants. This work implies the upconverter not only can serve as proof of principle for improving PCE of solar cells but also is helpful to practical application.