High Voc Research Articles

The Influence of the Vacuum Impregnation, Beetroot Juice, and Various Drying Methods on Selected Properties of Courgette and Broccoli Snacks.

The drying process is used in the food industry to extend the shelf life of fruits and vegetables without the use of preservatives. As quality, visual, and aroma characteristics are important determinants of consumer interest, they play a key role in the development of new foods. In the present study, vacuum impregnation (VI) was used prior to vacuum drying (VD) and freeze drying (FD) of courgette and broccoli. Organic beet juice was used to produce the novel snacks. The study showed that the use of vacuum impregnation significantly affected the VOCs profile (volatile organic compounds profile), in which the following compounds were found: viz: 2-(E)-hexen-1-ol, 2-(Z)-hexen-1-ol and aceto-phenone. VI caused a decrease in volumetric gel index (VGI), drying shrinkage (S), water activity (AW), decreased color saturation (∆C), and increased dry matter content (DM). All these properties testify to the positive effect of the pretreatment used. The drying methods used had a significant effect on the properties of the dried vegetables. The dries obtained by the FD method showed higher density and water activity, as well as better preserved color (lower ∆E) and higher VOCs, so it is considered that freeze drying is a suitable method for obtaining novel courgette and broccoli snacks.

Improved interface microstructure between crystalline silicon and nanocrystalline silicon oxide window layer of silicon heterojunction solar cells

N-type hydrogenated nanocrystalline silicon oxide (nc-SiOx:H) is potential to enhance the performance of silicon heterojunction solar cells, but the raised plasma damage on underlying layer during the nc-SiOx:H deposition with a high-volume fraction of hydrogen is a burning issue. The underlying intrinsic hydrogenated amorphous silicon (i-a-Si:H) bilayer between n-type crystalline silicon (c-Si) and n-type nc-SiOx:H has been investigated by modulating silane (SiH4) gas flow rate (GFR) of interface porous layer. It has been found that the initial H-rich i-a-Si:H bilayer deposited by interfacial 1600 sccm GFR with relatively stable larger voids diameter and less voids number density can not only withstand hydrogen ions bombardment but also passivate c-Si surface well. Meanwhile, it also has been verified that the optimal n-seed deposition can further enhance both total hydrogen content and hydrogen content in compact structure to promote c-Si surface passivation and carrier transportation. The optimized SiH4 GFR for the interfacial i-a-Si:H growth and the appropriate deposition time of n-seed layer have been applied into the front passivation layer of silicon heterojunction solar cells, thus a high efficiency of approximate 25 % with high VOC and FF has been achieved.

Semitransparent Perovskite Solar Cells with an Evaporated Ultra‐Thin Perovskite Absorber

AbstractMetal halide perovskites are of great interest for application in semitransparent solar cells due to their tunable bandgap and high performance. However, fabricating high‐efficiency perovskite semitransparent devices with high average visible transmittance (AVT) is challenging because of their high absorption coefficient. Here, a co‐evaporation process is adopted to fabricate ultra‐thin CsPbI3 perovskite films. The smooth surface and orientated crystal growth of the evaporated perovskite films make it possible to achieve 10 nm thin films with compact and continuous morphology without pinholes. When integrated into a p‐i‐n device structure of glass/ITO/PTAA/perovskite/PCBM/BCP/Al/Ag with an optimized transparent electrode, these ultra‐thin layers result in an impressive open‐circuit voltage (VOC) of 1.08 V and a fill factor (FF) of 80%. Consequently, a power conversion efficiency (PCE) of 3.6% with an AVT above 50% is demonstrated, which is the first report for a perovskite device of a 10 nm active layer thickness with high VOC, FF and AVT. These findings demonstrate that deposition by thermal evaporation makes it possible to form compact ultra‐thin perovskite films, which are of great interest for future smart windows, light‐emitting diodes, and tandem device applications.

Molecular engineering of tetraphenyl-based hole transporting materials to enhance photovoltaic properties of perovskite solar cells

Perovskite photovoltaic cells have lately gained appeal due to their excellent operational efficiency, photophysical properties, and high dielectric constant. Five novel hole transport materials namely TADM1–TADM5 were devised to improve power conversion efficiency (PCE) of Perovskite solar cells (PSCs). These molecules have tetraphenyl (TP) as a typical core, donor, and different acceptor units connected via a thiophene spacer. Under the framework of DFT theory, the B3LYP functional along with the 6–31 G basis set was utilized to study their geometries, molecular electrostatic potential, reorganization energies, the density of states, quantum chemical parameters, transition density matrix, binding energies, and charge transfer properties. All the designed HTMs (TADM1–TADM5) displayed excellent photovoltaic properties due to lower (Eg) varying (1.94–2.54 eV), small binding energies (0.04–0.36 eV), and high dipole moments (12.89 D to 26.93 D) that enhanced their electron charge transfer behavior. Small reorganization energy (RE) values for holes and electrons resulted in significant charge mobility. All the designed HTMs (TADM1-TADM5) have higher VOC (1.30–1.43 V) and power conversion efficiency (23.70–26.27%) than the reference molecule SMeTAD (20.94%). Consequently, all of the modelled molecules (TADM1-TADM5) demonstrate that using acceptor moieties is an effective method for achieving acceptable optoelectronic characteristics and outstanding efficiency.

Methoxy‐Based Passivator 4‐Methoxyphenethylammonium Iodide as Multifunctional Passivator for High‐Efficiency 3D/2D Flexible Perovskite Solar Cells over 23%

As is well known, the interface of perovskite solar cells (PSCs) is rich in deep‐level carrier traps, which act as non‐radiative recombination centers and limit the open‐circuit voltage (VOC) and power conversion efficiency (PCE) of PSCs. Defect chemistry and surface passivation agents have been extensively studied, primarily focusing on the neutralization of non‐coordinated lead or anion defects. Herein, a novel methoxy‐based passivator 4‐methoxyphenethylammonium iodide (p‐MeOPEAI) is introduced for a multifunctional passivation effect at the perovskite interface. It is susceptible for p‐MeOPEAI to form 2D perovskite on top of 3D perovskite, and it interacts with the surface of 3D perovskite in multiple ways, forming a 3D/2D structure that facilitates charge transfer and p‐MeOPEAI passivates the uncoordinated Pb2+ ions of the perovskite film surface. The interface defects in the PSCs are well passivated, minimizing non‐radiative recombination and enhancing device performance. As a result, a champion PCE of 23.3% is achieved for flexible PSCs with a high VOC (1.2 V). In addition, modified devices also show enhanced operational mechanical stability (retention of >80% initial PCE after 10 000 bending cycles).

Theoretical exploration of high VOC in Cu2SnS3 thin film solar cells towards high efficiency

This article manifests the outstanding performance of copper-tin-sulphide (Cu2SnS3)-based double-heterojunction (DH) photovoltaic cell. The n-type ZnSe as window and the p+-type CGS (CuGaSe2) as back surface field (BSF) layer have been used for the p-type Cu2SnS3 base layer. The SCAPS-1D simulator is used for the simulation of this photovoltaic cell and demonstrating the effects of each layer. The n-ZnSe/p-Cu2SnS3 heterojunction has displayed a power conversion efficiency (PCE) of 17.69 % with JSC = 32.39 mA/cm2, VOC = 0.60 V, and FF = 80.58 %, when functioning alone. An enrichment of PCE to 38.14 % has been observed, owing to the addition of CGS as aBSF layer in the proposed structure. The VOC also develops enormously to 1.22 V in dual-heterojunctions, which boosts the PCE. The effective band alignment between ZnSe/Cu2SnS3 and Cu2SnS3/CuGaSe2 interfaces produces greater built-in potential that is liable to generate high VOC. The built-in potential of the device is 1.54 V according to the C-V study. These outcomes imply that the n-ZnSe/p-Cu2SnS3/p+-CGS device would be a viable alternative for harvesting solar energy in the era of thin film solar cells.

Lowest Open‐Circuit Voltage Deficit Achievement to Attain High Efficient Antimony Selenosulfide Solar Cells

AbstractAntimony selenosulfide (Sb2(S,Se)3) solar cells bear great potential for sustainable photovoltaic technology, attributed to their excellent semiconductor properties. Despite the encouraging breakthroughs, the efficiency of Sb2(S,Se)3 solar cells still leaves much room for improvement due to the large open‐circuit voltage (VOC) deficit (the radiative VOC limit minus the high VOC). Herein, ammonium sulfide ((NH4)2S) solution is utilized to treat Sb2(S,Se)3 films to tailor their surface properties. The disappearance of the hole defect (H1) and the decrease of the defect concentration of hole defect (H2) confirm that non‐radiative recombination is suppressed greatly. Photovoltage decay lifetime is greatly increases from 67.9 to 297.9 µs. The upshifted valence band maximum optimizes the energy level alignment between the p–n heterojunction, enhancing the carrier transport. Remarkably, this treatment yields a record lowest VOC deficit of 0.49 V by now, and the best device with 10.41% efficiency, ca. 25% improvement over the control device (8.35%). This study provides valuable insight into reducing the VOC deficit in solar cells and related photoelectronic devices by minimizing non‐radiative recombination, and also presents a great potential strategy to achieve the lowest VOC deficit.

Zwitterion Reduces Open‐Circuit Voltage Loss in Wide‐Bandgap Perovskite Solar Cells with 22% Efficiency and Its Application in Tandem Devices

Wide‐bandgap (WBG) perovskite solar cells (PSCs) can be combined with other narrow‐bandgap cells to form tandem solar cells (TSCs), which have excellent commercialization prospects. However, the component of WBG perovskite is complex, and the crystallization process is difficult to control. Various bulk and surface defects in polycrystalline films lead to severe nonradiative recombination of photogenerated carriers, resulting in severe open‐circuit voltage (VOC) loss in WBG PSCs. Herein, a zwitterionic additive is introduced to alleviate the VOC deficit. The sulfinyl group (–SO) in formamidine sulfinic acid (FSA) has a robust interaction with Pb2+, which retards the crystallization and improves the crystal quality in perovskite films. Furthermore, FSA has negatively charged centers (–SO2−) and positively charged centers (–C(NH2)2+), which can passivate the halogen and cation vacancies, respectively. The improved crystalline quality and passivated defects reduce the capture of carriers by defects and facilitate higher VOC. With this strategy, the 1.68 eV bandgap PSCs achieve a champion efficiency of 22.06% and a high VOC of 1.25 V (VOC loss = 0.43 V). Moreover, the 2‐terminal perovskite/silicon TSCs are fabricated with an extraordinary power conversion efficiency of 28.81%.

Electronic structure and photophysical properties of some promising organic molecules for organic solar cells.

Three novel organic semiconductors (Fig. 1), which are molecule (a) and molecule (c) have the same wing unit molecules (b) and (c) have the same core unit were reported. Thus, the influence of wing units on solar cell device performance parameters such us the opto-electronics properties, non-linear optics (NLO), electronic properties, and natural bond orbitals (NBO) were calculated in order to evincing molecular structure-property relations. The all studied molecules would be promising materials for photovoltaic applications, but molecule (c) could be an excellent candidate for high efficiency organic solar cells with a small energy gap, a lowest ΔGreg, highest Voc, and LHE values. According to all these results, it is seen that the wing units of the molecules affect both the opto-electronic properties and NLO properties more than the core units. These theoretical calculations is expected to obtain new strategies to synthesize efficient materials for organic solar cell devices. Density functional (DFT) and time-dependent density functional (TDDFT) theory simulations for the solar cell device performance parameters, non-linear optics, and natural bond analysis were performed using the Gaussian 09w software. The ground state properties of molecules have been studied with hybrid functional of Beckethree-Lee-Yang-Parr (B3LYP), and excited state properties have been calculated CAMB3LYP and our DFT calculations were performed using 6-31++G(d,p) basis set on fully optimized geometries.

Flexible regenerated cellulose/ZnO based piezoelectric composites fabricated via an efficient one-pot method to load high-volume ZnO with assistance of crosslinking

Flexible piezoelectric film has broad application in the energy devices and sensor field. Herein, a highly effective “one-pot method” was proposed to fabricate regenerated cellulose/ZnO piezoelectric composites, in which the preparation of regenerated cellulose (RC), in-suit polymerization of ZnO in RC and its cross linking can be carried out simultaneously. ZnO were in-situ synthesized from Zn2+ reduced by alkali from the dissolve system of cellulose. Simultaneously, the added zinc salt accompanied with acid degradation has promoted the dissolution of cellulose, existing a synergistic effect. In this synthetic process, ECH was used to crosslink cellulose molecules to obtain cross-linked regenerated cellulose (CRC), which enhanced regenerated cellulose framework for more uniform hydroxyl groups as growth sites, thereby further elevate growth content of piezoelectric ZnO distributed uniformly in the composite film. Consequently, the piezoelectric constant (d33) of the developed piezoelectric composite film with excellent tensile strength and flexibility reaches 26.8 ± 6.4 pC N−1. Without external high-voltage polarization, its piezoelectric output open-circuit voltage (VOC) and short-circuit current (ISC) was increased to 6.98 V and 610.27 nA. After polydimethylsiloxane (PDMS) was immersed in the CRC/ZnO aerogel to be CRC/ZnO/PDMS PENG, the piezoelectric output performance was further enlarged to be 10.02 V and 1032.57 nA, respectively, even with a high output stability. It can drive a LED and a small electronic screen, as well as has high sensitivity to pressure excitation, displaying high VOC and ISC up to 17 V and 1300 nA under the trampled state, respectively. The strategy has brought highly efficient assembly and high performance for the piezoelectric nanogenerator (PENG), directly providing a reference to other nanocellulose based PENG.

Structural Transformation of PEDOT on Si/PEDOT:PSS Hybrid Solar Cells by Doping Hydroquinone

The PEDOT:PSS/Si hybrid solar cells (HSCs) have aroused wide concern due to their many unique advantages such as simple device structure and advantages of economic processing. Herein, the PEDOT:PSS/Si hybrid solar cells with extremely high open circuit voltage (Voc) are fabricated, novel hydroquinone (HQ) is blended as a dopant to improve the performance of HSCs. The results show that the structure of PEDOT changes from benzoid to quinoid, and than convert back into benzoid when PEDOT have more quinoid structure, the conductivity of PEDOT: PSS films is higher. The experimental results show that when doping the hydroquinone concentration is 2 wt%, the performance of the device is the best, power conversion efficiency is 13.12%, and Voc is 669.9 mV. In addition to improving the electrical properties of PEDOT:PSS films, HQ doping retains the work function of pure films and achieves a high Voc of HSC, which makes it different from the modified methods employed in previous reports.

Nanoscale Size Control of Si Pyramid Texture for Perovskite/Si Tandem Solar Cells Enabling Solution‐Based Perovskite Top‐Cell Fabrication and Improved Si Bottom‐Cell Response

AbstractA monolithic perovskite/silicon tandem solar cell architecture is employed to surpass the single‐junction efficiency limit. Recently, there is an increasing need for the double‐sided textures in the Si bottom cell to be compatible with the solution‐processed perovskite top cell from an industrial perspective. Herein, a silver‐assisted alkaline etching method is applied to fabricate nanoscale Si pyramid textures, and the influence of varying pyramid size (400–900 nm) on the interface morphology and the performance of perovskite/Si tandem cells is investigated. It is demonstrated that electrical shunting starts to increase, and the open‐circuit voltage (VOC) decreases when the texture size exceeds the perovskite thickness (~500nm) due to the non‐uniform top‐cell formation on a rough Si surface. However, when the texture size is reduced to 400–500 nm, all spin‐coated perovskite top‐cell component layers exhibit an even form over the nanopyramid Si, resulting in a high VOC and an enhanced Si bottom cell current (≈1.0 mA cm−2) due to the suppressed reflectance at the top/bottom cell interface without using optical couplers. The double‐sided nanopyramid Si texture offers opportunities to increase tandem cell efficiency while reducing its production cost compared with the commonly used single‐sided textured Si.

Predicting benzodithiophene based donor materials with enhanced 19.09% PCE, open-circuit voltage and optoelectronic attributes for solar cell applications: Photochemical insights from DFT

Seven benzo[1,2-b:4,5-b′]dithiophene (BDT) based novel donor (D1-D7) molecules with A-π-D-π-A configuration are investigated by DFT and TD-DFT methods and a power conversion efficiency (PCE) of 19.09% is predicted for organic solar cells (OSCs). The fundamental core of these novel compounds is the BDT molecule (R), with other significant acceptors substituted on the outer borders. To study the geometrical, photovoltaic, and optoelectronic properties of the newly designed sensitizers (D1-D7), the CAM-B3LYP/6-31G(d,p) method was employed for computational analysis and comparison with BDT (R) Evaluations were conducted on open circuit voltage (Voc), power conversion efficiency (PCE), fill factor (FF), absorption spectra, the distribution pattern of electron density, charge mobility, electron, and hole reorganizational energy, the density of state (DOS), frontier molecular orbital (FMO), and transition density matrices (TDM)of the investigated compounds. In comparison to the reference compound (R), D2, D3, and D4 have better optical and chemical characteristics. The DOS plots and the FMOs analysis showed that the addition of acceptor groups finely improved the charge distribution in the molecules under study. The optoelectronic characteristics of the proposed structure D2 in chloroform solvent were the most improved, with a lower band gap (3.87 eV), higher maximum absorbance (533 nm), and lower binding energy (1.55 eV) than others investigated. The TDM graphs revealed the reliability of the charge transfer capability. In several molecules, the mobilities of charge transfer in designed compounds were equivalent to the reference R while the D2 was the lowest among all implying that the charge carriers would be more maneuverable. For all donors, the Voc was calculated with PC71BM. Voc is high for D2, D3, and D4, compared to R. All investigated compounds were predicted to have remarkable PCEs with high FF values. Especially, D2 has the higher Voc (2.422 V) and FF (94.12), which leads to the highest PCE of 19.09%. Hence, all calculated characteristics are very favorable to the potential of our designed molecules in photovoltaic applications.

Design, synthesis, and performance evaluation of TiO2-dye sensitized solar cells using 2,2′-bithiophene-based co-sensitizers

We report on the synthesis and characterization of six novel 2,2′-bithiophene-based organic compounds (3a–c and 5a–c) that are designed to serve as co-sensitizers for dye-sensitized solar cells (DSSCs) based on TiO2. The compounds are linked to various donor and acceptor groups, and we confirm their chemical structures through spectral analyses. Our focus is on enhancing the performance of metal based N3, and the compounds were designed to operate at the nanoscale. We performed absorption and fluorescence emission measurements in dimethylformamide (DMF), where one of our compounds 5a exhibited the longest maximum absorption and maximum emission wavelengths, indicating the significant impact of the para methoxy group as a strong electron-donating group. Our dyes 5a + N3 (η = 7.42%) and 5c + N3 (η = 6.57%) outperformed N3 (η = 6.16%) alone, where the values of short current density (JSC) and open circuit voltage (VOC) for these two systems also improved. We also investigated the charge transfer resistance at the TiO2/dye/electrolyte interface using electrochemical impedance spectroscopy (EIS), which is important in the context of nanotechnology. According to the Nyquist plot, the 5a + N3 cocktail exhibited the lowest recombination rate, resulting in the highest VOC. Our theoretical calculations based on density functional theory (DFT) are also in agreement with the experimental process. These findings suggest that our compounds have great potential as efficient DSSC co-sensitizers. This study provides valuable insights into the design and synthesis of new organic compounds for use as co-sensitizers in DSSCs based on TiO2 and highlights the potential of these compounds for use in efficient solar energy conversion.

12.3% Efficient Low Voc Loss Pure Sulfide Kesterite Solar Cells from DMSO Solution via Cadmium Alloying

AbstractCd alloying has been theoretically proved to be an effective strategy to suppress Cu‐Zn antisite defects and related defect cluster for improving device performance of pure sulfide kesterite Cu2ZnSnS4 (CZTS) thin film solar cells. However, the potential of Cd alloying has not been fully realized by solely doping without further post heat‐treatment. Here, Cd alloying CZTS (Cu2(Zn,Cd)SnS4, CZCTS) is reported through dimethyl sulfoxide (DMSO) solution and how alloying concentration affects reaction path, grain growth, and electronic properties of the CZCTS absorbers is investigated. This study found that Cd can be incorporated into CZTS through direct phase transformation grain growth, which sufficiently suppresses band tailing. High quality CZCTS absorber films and efficient solar cells are fabricated within a wide range of alloy concentration. A champion CZCTS device with a power conversion efficiency of 12.3% is achieved at 35% Cd concentration without any post heat treatment, improved by over 70% compared to 7.0% of CZTS. This device exhibits a high VOC gain to the Shockley–Queisser (Voc/VocSQ = 59.7%), the lowest VOC deficit achieved in pure sulfide kesterite solar cells. The results demonstrate the importance of the Cd alloying strategy for mitigating band tailing and achieving high efficiency pure sulfide kesterite solar cells.

A combination of fluorine-induced effect and co-sensitization for highly efficient and stable dye-sensitized solar cells.

Developing dyes with high open-circuit photovoltage (Voc) is a vital strategy to improve the power conversion efficiency (PCE) of co-sensitized solar cells (co-DSSCs). Herein, three organic fluorine-containing dyes [YY-ThP(3F), YY-ThP(2F), and YY-ThP(26F)] are designed and synthesized for investigating the fluorine-induced effect on photophysical and photovoltaic performances. Consequently, this effect can significantly broaden the UV-vis absorption spectra of dyes but fail to improve the light-harvesting capability of DSSCs. Strikingly, YY-ThP(3F), featuring 3-position fluorine substitution to cyanoacrylic acid, yields a relatively high Voc compared to the corresponding fluorine-free dye (YY-ThP). Furthermore, the co-sensitization of YY-ThP+YY-ThP(3F) achieves a remarkably high PCE and long-term stability. This work implies that the combination of judicious molecular engineering and co-sensitization is a promising strategy for highly efficient and stable DSSCs.

High‐Voltage Quasi‐Solid‐State Dye‐Sensitized Solar Cells Based on Copper Redox Shuttles

Electrolyte with copper redox shuttles has endowed dye‐sensitized solar cells (DSSCs) with a high open‐circuit voltage (V oc) over 1.0 V and promising efficiencies under the sun and indoor light, but further combining these copper redox shuttles with quasi‐solid‐state gel polymer electrolytes (GPEs) is still a great challenge. The crystallization of polymers inside GPEs is one of the important factors to limit the mass transport of large‐sized copper redox shuttles and dramatically reduce the efficiency of quasi‐solid‐state DSSCs. Herein, the copper‐based GPEs are fabricated via in situ UV‐induced copolymerization of acrylic monomers. This chemical cross‐linking strategy can significantly reduce the crystallinity of polymers inside the GPEs and thus improve the apparent diffusion coefficient two times compared with the generally used poly(ethylene oxide) GPEs. Finally, optimized GPEs, copolymerized by diacrylic and triacrylic monomers, successfully generate the quasi‐solid‐state DSSCs with an efficiency of 10.1% and a high V oc of 1.03 V. These photovoltaic parameters are comparable to those of DSSCs with liquid copper‐based electrolytes, demonstrating that the chemical cross‐linking is an effective strategy to fabricate high‐performance copper‐based GPEs. This strategy will facilitate the future efficiency and stability improvement of DSSCs for the commercial optoelectronic applications.

Triple-electrode integrated self-supporting triboelectric nanogenerators with high output and durability based on dynamic supercritical carbon dioxide foaming

Durable and sustainable energy harvesting in harsh environments using triboelectric nanogenerators (TENGs) is a grand challenge. Herein, highly compacted and integrated TENGs are developed using dynamic supercritical carbon dioxide (scCO2) foaming technique. The self-assembled internal-electrode TENG (SAI-TENG) which is consisted of a polydimethylsiloxane (PDMS) coated internal metal electrode covered by a corrugated wrinkled foam (CWF) is readily obtained by the foaming process. The CWF can support itself and maintains air gaps to facilitate contact electrification and the biomimetic wrinkles that are induced by the scCO2 flow field, greatly enhance the triboelectric output performance. By sandwiching the SAI-TENG using two internal-electrode PDMS films, a triple-electrode integrated self-supporting TENG (TIS-TENG), which has eight-friction layers in a single device, is developed. The TIS-TENG realized maximum utilization of the wrinkled CWF surface, which is equivalent to three parallel connected TENGs. Moreover, the output was further boosted by adding tea powders and patterning micro domes on the PDMS films, which resulted in a high Voc of 106.3 V and a power density of 32.5 mW/m2. Attributing to the embedded electrode and high elasticity of CWF, the TIS-TENG has remarkable stability and tolerance to harsh conditions and can be used as self-powered sensors for monitoring vehicle parking and working conditions of workers. This work provides new insights into the green fabrication and development of highly integrated self-supporting TENGs with high performance and durability.

SnF2‐Doped Cs2SnI6 Ordered Vacancy Double Perovskite for Photovoltaic Applications

Air‐stable p‐type SnF2:Cs2SnI6 with a bandgap of 1.6 eV has been demonstrated as a promising material for Pb‐free halide perovskite solar cells. Crystalline Cs2SnI6 phase is obtained with CsI, SnI2, and SnF2 salts in gamma‐butyrolactone solvent, but not with dimethyl sulfoxide and N,N‐dimethylformamide solvents. Cs2SnI6 is found to be stable for at least 1000 h at 100 °C when dark annealed in nitrogen atmosphere. In this study, Cs2SnI6 has been used in a superstrate n–i–p planar device structure enabled by a spin‐coated absorber thickness of ≈2 μm on a chemical bath deposited Zn(O,S) electron transport layer. The best device power conversion efficiency reported here is 5.18% with VOC of 0.81 V, 9.28 mA cm−2 JSC, and 68% fill factor. The dark saturation current and diode ideality factor are estimated as 1.5 × 10−3 mA cm−2 and 2.18, respectively. The devices exhibit a high VOC deficit and low short‐circuit current density due to high bulk and interface recombination. Device efficiency can be expected to increase with improvement in material and interface quality, charge transport, and device engineering.

Illumination Enhanced Crystallization and Defect Passivation for High Performance CsPbI3 Perovskite Solar Cells by Sacrificing Dye

AbstractAll‐inorganic perovskite solar cells (PSCs) have been the research focus due to their high thermal stability and proper band gap for tandem solar cells. However, their power conversion efficiency (PCE) is still lower than that of organic‐inorganic hybrid PSCs. Herein, a sacrificing dye (Rhodamine B isothiocyanate, RBITC) is developed to regulate the growth of perovskite film by in situ release of ethylammonium cations, isothiocyanate anions and benzoic acid molecules upon annealing and illumination. The ethylammonium cations can efficiently passivate surface defects. The isothiocyanate anions incorporate with uncoordinated Pb to regulate the crystallization process. The benzoic acid molecules facilitate the nucleation of the perovskite crystals. Especially, the illumination can accelerate the release of these beneficial ions/molecules to improve the quality of perovskite films further. After optimization with RBITC, a high open circuit voltage (VOC) of 1.24 V and a champion PCE of 20.95% are obtained, which are among the highest Voc and PCE values of CsPbI3 PSCs. Accordingly, the operational stability of the PSC devices is significantly improved. The results provide an efficient chemical strategy to regulate the formation of perovskite films in whole crystallization process for high performance all‐inorganic PSCs.