Reduced Carrier Recombination Research Articles

Mixed Dimensional Perovskites Heterostructure for Highly Efficient and Stable Perovskite Solar Cells

Heterojunctions constructed upon multidimensional perovskites (1D/3D or 2D/3D) has emerged as an effective approach to improve the photovoltaic performance and stability of perovskite solar cells (PSCs). Herein, 1D trimethyl sulfonium lead triiodide (Me3SPbI3) 1D Me3SPbI3 nanoarrays are successfully synthesized via a two‐step method in aqueous condition, which reflects excellent water resistivity and environmental stability. By incorporating this 1D Me3SPbI3 into lead halide 3D perovskites, heterostructural 1D/3D perovskite photoactive layer with improved morphology, crystallinity, enhanced photoluminescence lifetime, and reduced carrier recombination in comparison to its 3D counterpart is obtained. Moreover, an efficient and stable 1D/3D PSCs with power conversion efficiency (PCE) of 22.06% by using this 1D/3D perovskite are demonstrated. It noticeably maintained 97% of their initial efficiency after 1000 h storage under ambient condition (RH≈50%) without encapsulation. Our study opens up the design protocol for the development of next‐generation highly efficient and stable perovskite solar cells.

Reveal the large open-circuit voltage deficit of all-inorganic CsPbIBr2 perovskite solar cells

Due to excellent thermal stability and optoelectronic properties, all-inorganic perovskite is one of the promising candidates to solve the thermal decomposition problem of conventional organic-inorganic hybrid perovskite solar cells (PSCs), but the larger voltage loss (V loss) cannot be ignored, especially CsPbIBr2, which limits the improvement of efficiency. To reduce V loss, one promising solution is the modification of the energy level alignment between the perovskite layer and adjacent charge transport layer (CTL), which can facilitate charge extraction and reduce carrier recombination rate at the perovskite/CTL interface. Therefore, the key issues of minimum V loss and high efficiency of CsPbIBr2-based PSCs were studied in terms of the perovskite layer thickness, the effects of band offset of the CTL/perovskite layer, the doping concentration of the CTL, and the electrode work function in this study based on device simulations. The open-circuit voltage (V oc) is increased from 1.37 V to 1.52 V by replacing SnO2 with ZnO as the electron transport layer (ETL) due to more matching conduction band with the CsPbIBr2 layer.

Chemical etching induced surface modification and gentle gradient bandgap for highly efficient Sb2(S,Se)3 solar cell

Recently, due to its excellent photovoltaic features, Sb2(S,Se)3 is regarded as a promising photovoltaic absorber material. However, the interfacial property of Sb2(S,Se)3-based solar cell still needs to be studied due to limited efficiency improvement resulting from interfacial defects. In this paper, we focus on Sb2(S,Se)3 film prepared by hydrothermal method to investigate the effects of surface modification on the properties of the Sb2(S,Se)3 film as well as its solar cell performance. Interestingly, the chemical etching performed on Sb2(S,Se)3 film using potassium fluoride aqueous solution not only improved the crystallinity and uniformity of Sb2(S,Se)3 film but also decreased the interfacial defects, leading to a reduced carrier recombination loss of the device. As a result of chemical modification, the current density and fill factor of Sb2(S,Se)3-based superstrate structure solar devices were improved, resulting in maximum efficiency of 9.58%. Overall, this research offers a comprehensive understanding of the hydrothermally processed Sb2(S,Se)3 film as well as a viable alternative method for reducing interfacial defects in other chalcogenide semiconductors.

On the role of carboxylated polythiophene in defect passivation of CsPbI 2 Br surface for efficient and stable all‐inorganic perovskite solar cells

Improved film surface is a prerequisite to achieve high photovoltaic performance of inorganic perovskite solar cells because defective (under-coordinated) lead ions derived from imperfect lattice structure of the film surface or grain boundaries the principal nonradiative recombination centers in the inorganic perovskite absorber. In this study, we suggest poly[3-(4-carboxybutyl)thiophene-2,5-diyl] (P3CT), a carboxylated p-type conjugated polymer, as a passivating agent of the CsPbI2Br layer to tailor electronic properties of a perovskite absorber. With the P3CT passivation, the defective sites of the perovskite film surface were improved and stabilized, which can suppress nonradiative recombination to promote charge transport of CsPbI2Br-based all-inorganic perovskite solar cells. Consequently, the P3CT passivation delivers a power conversion efficiency (PCE) of 12.25% and decent long-term stability of CsPbI2Br perovskite solar cells, which surpasses the pristine device without the passivation. The electricity generation capability under indoor light source of the passivated device is also studied, demonstrating a promising PCE of 27.47%. This work unveils the role of P3CT as a passivating agent to passivate the defective sites of CsPbI2Br perovskite film surface and grain boundaries, which facilitates charge transport and reduced carrier recombination of CsPbI2Br absorber in solar cell devices.

In-situ grown nanoscale p-n heterojuction of Cu2S-TiO2 thin film for efficient photoelectrocatalytic H2 evolution

Nanoscale heterojuction thin film of Cu2S-TiO2 has been grown by sol-gel technique and has been employed for efficient H2 production through water splitting. This nanoscale heterojunction has been grown in three steps which include ion conducting Li4Ti5O12 thin film deposition and ion-exchange (Li+↔Cu+) followed by a sulfurization process. To study the photoelectrochemical performance of this Cu2S-TiO2 heterojunction thin film, photoanodes were fabricated on TiO2 coated FTO substrate. The TiO2 film was deposited by two different methods - the sol-gel method and colloidal TiO2 nanoparticles (TiO2NP). Highest photocurrent of ∼36 mAcm−2 was obtained by Cu2S-TiO2/TiO2NP/FTO photoanode under 0.5 V potential (E Vs. RHE, 1 M KOH). The photocurrent is ∼103 times higher compared to that of the bare TiO2 photoanode and stable for several hours. The photoelectrochemical (PEC) behavior is much higher with respect to previous reports on Cu2S (NP)-TiO2 nanocomposite photoanodes, which is due to the significant reduction in carrier recombination at the electronically coupled Cu2S-TiO2 heterojunction interface.

Minimizing the Voltage Loss in Hole‐Conductor‐Free Printable Mesoscopic Perovskite Solar Cells

AbstractThe hole‐conductor‐free printable mesoscopic perovskite solar cells based on the inorganic scaffolds of mesoporous titania, mesoporous zirconia, and porous carbon have attracted much attention due to their excellent stability and low manufacturing cost. However, in such hole‐conductor‐free devices, the transport of the photogenerated holes is dominated by the diffusion‐assisted charge carrier movement, while the driving force is insufficient. Reinforcing the built‐in electric field (BEF) is an effective strategy to promote oriented carrier transport. Herein, by using an optimized two‐step deposition method, the BEF is reinforced by creating a work function difference of perovskite (Δµ) in different layers via a gradient self‐doping. The enhanced BEF improves the hole transport and extraction, and significantly reduces the carrier recombination losses in the device. As a result, an average open‐circuit voltage improvement over 60 mV and a power conversion efficiency of 17.68% are achieved without any additives or complex processes. This strategy provides a new approach toward fabricating highly efficient printable mesoscopic perovskite solar cells with reduced carrier recombination losses.

Size mismatch induces cation segregation in CsPbI3: Forming energy level gradient and 3D/2D heterojunction promotes the efficiency of carbon-based perovskite solar cells to over 15%

The application of CsPbI 3 inorganic perovskite in carbon-based perovskite solar cells without hole transporter (C-PSCs) is expected to enhance device stability. However, due to the lower hole selectivity of carbon electrode than that of hole transporter, the efficiency of CsPbI 3 C-PSCs is significantly suppressed. Herein, size mismatch-induced cation segregation in CsPbI 3 is studied and employed to solve the problem. After treating CsPbI 3 with CsX (X Br, Cl and F) ethanol solutions, the larger size mismatch between X - and I - ions would induce the more obvious cation segregation. The moderate size mismatch between I - and Cl - ions allows a partial substitution of I - ions with Cl - ions in CsPbI 3 to form energy level gradient, and the CsCl residue on the surface tends to react with CsPbI 3 to generate 2D Cs 2 PbI 2 Cl 2 nanosheets, serving as an electron blocking layer. The synergistic effect of the energy level gradient and the electron blocking layer well improves hole selectivity at CsPbI 3 /carbon interface to reduce carrier recombination loss. As a result, the C-PSCs based on the CsCl-treated CsPbI 3 achieve an efficiency of 15.23%, a record value for inorganic C-PSCs. • The larger size mismatch between Br, Cl, F and I ions is found to induce cation segregation after CsX post treatment. • The moderate size mismatch leads to substitution of I with Cl in CsPbI 3 and form composition and energy level gradient. • The CsCl residue on the surface tends to react with CsPbI 3 to form 2D Cs 2 PbI 2 Cl 2 nanosheets as an electron blocking layer. • The energy level gradient and electron blocking layer improves the hole selectivity to reduce recombination loss. • The C-PSCs based on the CsCl-treated CsPbI 3 achieve an efficiency of 15.2%, a new record for inorganic C-PSCs.

Favorable grain growth of thermally stable formamidinium-methylammonium perovskite solar cells by hydrazine chloride

Formamidinium methylammonium lead iodine (FAMAPbI3) based perovskite solar cells have reached phenomenal efficiencies recently. However, it is difficult to form pure black α-phase perovskite by solution method. Meanwhile, the formed polycrystalline FAMAPbI3 film often has large amount of grain boundaries, which can consist dangling bonds and iodide ions. Under illumination and heat, iodide ions can easily migrate and oxidize to form iodine, thus decompose the structure of perovskite and reduce the device performance. Herein, hydrazine chloride (HACl) as an additive is employed to promote favorable grain orientation during the growth of perovskite crystals. From grazing incidence wide-angle X-ray scattering (GIWAXS) and scanning electron microscope (SEM), HACl can facilitate strong diffraction signals along crystallographic planes (100) and (200) indicating a strengthened lattice structure for α-phase FAPbI3 and significantly decrease the grain boundaries for reduced carrier recombination. Consequently, the perovskite solar cells (PSCs) with optimized content of HACl lead to a champion power conversion efficiency (PCE) of 22.32% (certified PCEs of 21.59%) in a mesoporous device based on (FAPbI3)0.95(MAPbBr3)0.05 perovskite solar cells. Furthermore, from UV–vis and XPS spectrum, HACl can reduce iodine (I0) to iodide (I-) effectively, meaning the process of decomposition of FAMAPbI3-based perovskite has been greatly inhibited. As a result, unencapsulated device can retain 95% of its original power conversion efficiency after 1400 h of continuous one-sun illumination. Meanwhile, thermal (60 °C) stability is also greatly improved by maintaining 90% of initial efficiency after aging for 1400 h.

Extensive Enhancement in Charge Collection Efficiency of Ferroelectric Cr-Doped BFO-Based Solar Cells by Using TiO2 Nanotube Arrays

In this article, 100 times or above enhancement in current has been reported in comparison to any of the previously reported BFO-based PV device. This was achieved by fabricating a novel heterostructure junction between ferroelectric Cr-doped BFO (BFCrO) and TiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> nanotubes (T-NTs). The device performance is also compared with BFO/T-NTs junction as well. The Ag/BFO (or BFCrO)/T-NTs/Ti PV cells were developed with BFO (or BFCrO) as the absorber layer, T-NTs were employed as the electron transport layer, with Ti substrate and Ag as bottom and top electrodes, respectively. The remarkable performance of the p-BFCrO/n-T-NTs junction was due to higher absorption in the visible spectrum owing to the stronger ferroelectricity in BFCrO and the large surface area-to-volume ratio of T-NTs. The photovoltaic (PV) performance revealed enhanced current density (J <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">SC</sub> ) and photovoltage (V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">OC</sub> ) of 7.6 mA/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> and 0.85 V, respectively. The structural, morphological, and optical properties of both the fabricated structures have been investigated and compared. A well-fitted band structure was realized for the fabricated devices illustrating the band dynamics and carrier flow generation at the interface. The impedance properties confirmed a substantial improvement in the interfacial charge transfer kinetics with an amended driving force for electron-hole pair separation. The enhanced PV performance can be ascribed to the synergetic effect between the polarization induced switching of Cr doping in BFO and the reduced carrier recombination stimulated by highly conductive T-NTs. The structure presented here is promising for developing low cost and efficient PV devices suitable for green energy harvesting applications.

Improved Charge Transport and Reduced Carrier Recombination of Nonfullerene Organic Solar Cells with the Binary Solvent

Improved Charge Transport and Reduced Carrier Recombination of Nonfullerene Organic Solar Cells with the Binary Solvent

Sulfur-doped photocatalysts with iron-nitrogen coordination bonds by modifying graphitic carbon nitride obtained from ammonium thiocyanate pyrolysis with ferrous sulfate heptahydrate in ethanol

The photocatalytic agent graphitic carbon nitride (g-C 3 N 4 ) was synthesized by pyrolysis of ammonium thiocyanate (NH 4 SCN) which is commonly produced via extraction of desulfurization waste liquids as the main salt. The g-C 3 N 4 photocatalyst was modified by treatment with different amounts of ferrous sulfate heptahydrate in ethanol, which resulted in Fe-doping and a certain degree of S-doping of the material. According to the characterization results, the modified sample eg-C 3 N 4 /FeSO 4 -10% with superior photocatalytic efficiency exhibited the highest specific surface area and pore volume, poor crystallinity, and a good sample polymerization degree. The existence of more C defect vacancies in the modified sample structure increased the electron density around C and N atoms in the triazine ring structure and becomes the electron capture center. At the same time, the presence of ethanol solvent promotes the formation of more Fe–N coordination bonds between a large number of lone pair electrons and metal Fe ions. In addition, with the increase of the doping amount of S element, a new impurity level is introduced, and the band gap widths of the samples become narrower. The changes of surface structure and energy band structure of the modified samples led to a significantly reduced carrier recombination rate and further promoted the production of more reactive oxygen groups. In the process of Rhodamine B (RhB) degradation as organic pollutant, the degradation can reach 98% rapidly after 60 min of visible light irradiation, which is 78% higher than g-C 3 N 4 , at a simultaneous increase of the photocatalytic reaction rate constant from 0.007 to 0.305 per min. Meanwhile, the sample eg-C 3 N 4 /FeSO 4 -10% also showed excellent photocatalytic activity in the NO x removal process of air pollution. Compared with the original g-C 3 N 4 , the NO removal rate increased from 64% to 75%, and the production amount of harmful intermediate NO 2 decreased from 0.15 to 0.08 mg/m 3 . • Treatment of water and gas pollutants through waste. • Doping S element brings impurity level and band gap decreases. • The central N atom of the structure forms a Fe–N (III) coordination bond with Fe 3+ . • More Fe–N(III) can be formed by loading Fe metal ion in ethanol solvent. • The carrier compound rate of modified samples treated with ethanol solvent was lower.

Design of Grating Al2O3 Passivation Structure Optimized for High-Efficiency Cu(In,Ga)Se2 Solar Cells.

In this paper, we propose an optimized structure of thin Cu(In,Ga)Se2 (CIGS) solar cells with a grating aluminum oxide (Al2O3) passivation layer (GAPL) providing nano-sized contact openings in order to improve power conversion efficiency using optoelectrical simulations. Al2O3 is used as a rear surface passivation material to reduce carrier recombination and improve reflectivity at a rear surface for high efficiency in thin CIGS solar cells. To realize high efficiency for thin CIGS solar cells, the optimized structure was designed by manipulating two structural factors: the contact opening width (COW) and the pitch of the GAPL. Compared with an unpassivated thin CIGS solar cell, the efficiency was improved up to 20.38% when the pitch of the GAPL was 7.5–12.5 μm. Furthermore, the efficiency was improved as the COW of the GAPL was decreased. The maximum efficiency value occurred when the COW was 100 nm because of the effective carrier recombination inhibition and high reflectivity of the Al2O3 insulator passivation with local contacts. These results indicate that the designed structure has optimized structural points for high-efficiency thin CIGS solar cells. Therefore, the photovoltaic (PV) generator and sensor designers can achieve the higher performance of photosensitive thin CIGS solar cells by considering these results.

Enhancement in the efficiency of Sb2Se3 solar cell with the adding of high electrical concentration CdS:Al film

As a new general photovoltaic, antimony selenide (Sb2Se3) thin-film solar cell is now limited by the open-circuit voltage (Voc). In this study, an ultra-thin CdS:Al film obtained by co-sputtering CdS and Al targets as a N+ layer was employed in Sb2Se3 thin-film solar cells. The desposition condition of CdS:Al was optimised and solar cells with FTO/CdS:Al/CdS/Sb2Se3/Au structure were fabricated. Compared with the device without an N+ layer, the device with the N+ layer exhibited preferable photoelectric response, enlarged depletion-region width, better diode quality and reduced carrier recombination. As a result, improvements of 19% in Voc and 30% in efficiency of the Sb2Se3 thin-film solar cell were realised.

Achieving over 10 % Efficiency in Poly(3-hexylthiophene)-Based Organic Solar Cells via Solid Additives.

The photovoltaic performance of organic solar cells (OSCs) based on poly(3-hexylthiophene) (P3HT) has been steadily improved by developing novel non-fullerene acceptors (NFAs) in recent years. Herein, to further improve the performance of P3HT-based OSCs, a solid additive (SA4) and a typical solvent additive [1,8-diiodooctane (DIO)] were employed to process P3HT:ZY-4Cl-based OSCs, respectively. In comparison with the DIO-processed device, the SA4-processed one exhibited a more ordered molecular packing and more favorable phase separation, leading to enhanced charge transport and reduced carrier recombination. As a result, the SA4-processed device delivered a power conversion efficiency (PCE) of 10.24 %, which was much higher than that of the DIO-processed counterpart (6.26 %). This work reported a PCE over 10 % in P3HT-based OSCs for the first time, indicating the promising development of P3HT-based OSCs by morphological modulation.

Solar cells based on n+-AZO/p-BaSi2 heterojunction: Advanced opto-electrical modelling and experimental demonstration

We performed advanced opto-electrical simulations on thin-film BaSi 2 solar cells. First, absorption spectra of BaSi 2 - pn homojunction solar cells on Si substrate were calculated based on flat and/or pyramidally-textured surfaces, wherein 20-nm-thick n + -BaSi 2 was the topmost electron transport layer. By changing the front surface structure from flat to texture, the reflectance decreased in the wavelength ( λ ) range 700–1200 nm and the photocurrent density ( J ph ) delivered by the photogenerated carriers in the 500-nm thick p -BaSi 2 layer increased by 1.2 mA/cm 2 . Simulations revealed that the key factor inhibiting light absorption in the p -BaSi 2 layer was parasitic absorption in the n + -BaSi 2 and in the c-Si substrate. To solve these optical issues, we propose a new device structure, Al-doped n + -ZnO (AZO, 50 nm)/ i -ZnO (20 nm)/ p -BaSi 2 (500 nm) heterojunction solar cell (HJSC). In this device structure, the parasitic absorption reduced drastically, and J ph reached 30.23 mA/cm 2 . Furthermore, by replacing the Si substrate with a glass substrate, the light trapping worked more effectively, and the absorber layer thickness required for J ph to saturate was reduced to 1 μm, yielding 32.06 mA/cm 2 . Based on these simulation results, we manufactured n + -AZO/ p -BaSi 2 HJSC. The internal quantum efficiency exceeded 30% at λ = 600 nm, meaning that we demonstrated the operation of n + -AZO/ p -BaSi 2 HJSC for the first time. We investigated origins of small efficiencies compared to those simulated, and found that the passivation of defects in the p -BaSi 2 layer and the reduction of carrier recombination at the i -ZnO/ p -BaSi 2 interface would significantly improve the solar cell performance. This paper presents n + -AZO/p-BaSi 2 heterojunction solar cells (HJSC) to solve parasitic absorption in the n + -BaSi 2 and in the c-Si substrate of a BaSi 2 -pn homojunction solar cell. By replacing the Si substrate with a glass substrate, the light trapping works more effectively, and the absorber layer thickness required for photocurrent density to saturate can be reduced to 1 μm, yielding 32.06 mA/cm 2 . We manufactured n + -AZO/p-BaSi 2 HJSC, and demonstrated its operation for the first time. • We performed opto-electrical simulation on BaSi 2 pn-junction solar cells with flat and/or pyramidally-textured structure. • Parasitic absorption in the topmost layer significantly decreases the photocurrent density. • A new device structure, Al-doped n-ZnO/p-BaSi 2 , is proposed and demonstrated. • The importance of the carrier accumulation reduction at the ZnO/BaSi 2 interface is discussed.

Study of defect properties and recombination mechanism in rubidium treated Cu(In, Ga)Se2 solar cells

Heavy alkali-metal treatment of Cu(In,Ga)Se2 (CIGSe) absorbers has been emerging as a key process for achieving over 23% high conversion efficiencies in CIGSe solar cells. Here, we investigate the effect of rubidium fluoride post-deposition treatment (RbF-PDT) on the electronic and carrier recombination properties of narrow bandgap (narrowgap) gap and wide bandgap (widegap) CIGSe solar cells using thermal admittance spectroscopy (TAS), transient photocapacitance spectroscopy (TPC), as well as time-resolved photoluminescence (TRPL). We find that the activation energy of the main capacitance step in TAS spectra of narrowgap and widegap CIGSe solar cells reduces after RbF-PDT. On the other hand, capacitance–voltage (C–V) and temperature-dependent current–voltage (IVT) measurements demonstrate that the built-in potential, as well as the activation energy Ea, increases upon RbF-PDT both for narrowgap and widegap samples, pointing to reduced interface recombination. TPC revealed an appreciable reduction of the optical response of bulk defects in the narrowgap and widegap CIGSe, suggesting improvement of bulk properties after RbF treatment. TRPL confirmed that RbF-PDT significantly reduces carrier recombination in the bulk of narrowgap and widegap CIGSe absorbers and at the surface, leading to extended carrier lifetimes. Analysis of open-circuit voltage (VOC) losses due to nonradiative recombination in the bulk of the CIGSe showed a strong correlation between enhanced carrier lifetime and improved VOC for narrow gap CIGSe cells. In contrast, although we observed a substantial decrease of VOC losses in widegap CIGSe bulk, the analysis indicated that the key to photovoltaic performance enhancement is improved interface quality.

Numerical Simulation and Performance Evaluation of Highly Efficient Sb2Se3 Solar Cell with Tin Sulfide as Hole Transport Layer

This work reports a numerical investigation on the performance of Sb2Se3‐based thin‐film heterojunction solar cell using the solar cell capacitance simulator in 1D (SCAPS‐1D) program. Herein, inorganic tin sulfide (SnS) is introduced as a new hole transport material into the Sb2Se3 solar cell. The effects of several parameters such as thickness, doping, electron affinity, defect density, temperature, and resistances on the cell performances are analyzed. The proposed novel solar configuration that consists of Al/F:SnO2 (FTO)/CdS/Sb2Se3/SnS/Mo reveals the enhanced photovoltaic performances by means of reducing carrier recombination loss at back surface. At an optimized Sb2Se3 thickness of 1.0 μm, the efficiency is boosted from 24.01% to 29.89% by incorporating an ultrathin 0.05 μm SnS hole transport layer (HTL) into the Sb2Se3 solar cell. The performances of the proposed device are also evaluated by varying defects at CdS/Sb2Se3 and Sb2Se3/SnS interfaces. Moreover, it is found that electron affinity larger than 3.5 eV of HTL as well as back contact metal work function ≥4.9 eV should be considered to attain better performance. The simulated results lead to suggest that introducing the SnS material as a potential HTL candidate would be useful to develop low‐cost and highly efficient thin‐film solar cells.

SnS quantum dots with different sizes in active layer for enhancing the performance of perovskite solar cells

Because of the special low-dimensional physical properties of quantum dots (QDs) and the excellent optoelectronic properties of perovskite, the combination of perovskite solar cells (PSCs) and QDs may largely be one of the breakthroughs in device performance. However, little attention has been paid to the effect of the size of QDs on device performance except for bandgap tuning. In this work, non-toxic SnS QDs of different sizes were prepared by varying the reaction temperature of the thermal injection method. Their optical bandgaps with sizes were investigated, and they were implanted into the active layers of the carbon-based PSCs without hole transport layer. The effects of implanting SnS QDs with different sizes on the perovskite film quality and PSCs performance were studied. The cells implanted with SnS QDs of the best size (average 6.9 nm) achieved a photoelectric conversion efficiency of 14.26%, reaching a 12.42% improvement. The improved performance was mainly attributed to the presence of SnS QDs, which provided more nucleation sites for the growth of perovskite grains, and contributed to better quality perovskite films (including higher crystallinity, increased grain numbers and fewer surface defects), thus improving the light utilization, accelerating carrier transfer and reducing carrier recombination in the active layers. The successful implantation of QDs with different sizes in this paper has facilitated the development of the combination of perovskite and QDs in mesoporous PSC.

Enhancement of Photovoltaic Current through Dark States in Donor‐Acceptor Pairs of Tungsten‐Based Transition Metal Di‐Chalcogenides

AbstractAs several photovoltaic materials experimentally approach the Shockley–Queisser limit, there has been a growing interest in unconventional materials and approaches with the potential to cross this efficiency barrier. One such candidate is dark state protection induced by the dipole–dipole interaction between molecular excited states. This phenomenon has been shown to significantly reduce carrier recombination rate and enhance photon‐to‐current conversion, in elementary models consisting of few interacting chromophore centers. Atomically thin 2D transition metal di‐chalcogenides (TMDCs) have shown great potential for use as ultra‐thin photovoltaic materials in solar cells due to their favorable photon absorption and electronic transport properties. TMDC alloys exhibit tunable direct bandgaps and significant dipole moments. In this work, the dark state protection mechanism has been introduced to a TMDC based photovoltaic system with pure tungsten diselenide (WSe2) as the acceptor material and the TMDC alloy tungsten sulfo‐selenide (WSeS) as the donor material. Our numerical model demonstrates the first application of the dark state protection mechanism to a photovoltaic material with a photon current enhancement of up to 35% and an ideal photon‐to‐current efficiency exceeding the Shockley–Queisser limit.

CsPbBr3-MoS2-GO nanocomposites for boosting photocatalytic degradation performance

In order to address the main challenge of weak photocatalytic performance of pure metal halide perovskite materials, we innovatively introduced MoS2-graphene oxide (GO) composite structure and synthesized CsPbBr3-MoS2-GO nanocomposites by a two-step method. XRD and Raman results show that the three components are well combined to form a new CsPbBr3-MoS2-GO nanocomposite. TEM results show that MoS2 nanoribbons and CsPbBr3 quantum dots (QDs) are uniformly dispersed on the GO sheet. The photocatalytic activity of nanocomposites was evaluated by studying the photodegradation of Sudan Red III under xenon lamp irradiation. Benefiting from abundant active interfaces, the nanocomposites show much excellent photocatalytic degradation performance compared with pure CsPbBr3 QDs. The degradation rate of Sudan Red III by CsPbBr3-MoS2-GO nanocomposites is 3.1 times of that of pure perovskite QDs. Sudan Red III was completely photocatalytic degraded in 100 min. We believe that GO, with suitable band structure, high conductivity and good dispersibility, can bridge well MoS2 and CsPbBr3, act as a good electron transport channel, reduce carrier recombination and ultimately boost photocatalytic performance.