shuhui

Hole‐transport material based on dibenzo[b,d]thiophene (DBTMT) is synthesized with low costs. A champion power conversion efficiency of the optimized p–i–n planar perovskite solar cells based on dopant‐free DBTMT reaches 21.12% with a high fill factor of 83.25%, due to good hole‐transport properties and the passivation effect of DBTMT.

N ²,N ²,N ⁸,N ⁸‐tetrakis(4‐(methylthio)phenyl)dibenzo[b,d]thiophene‐2,8‐diamine (DBTMT) is synthesized from three commercial monomers for application as a promising dopant‐free hole‐transport material (HTM) in perovskite solar cells (pero‐SCs). The intrinsic properties (optical properties and electronic energy levels) of DBTMT are investigated, proving that DBTMT is a suitable HTM for the planar p–i–n pero‐SCs. The champion power conversion efficiency (PCE) of the optimized pero‐SCs (with structure as ITO/pristine DBTMT/MAPbI₃/C₆₀/BCP/Ag) reaches 21.12% with a fill factor (FF) of 83.25%, which is among the highest PCEs and FFs reported for planar p–i–n pero‐SCs based on dopant‐free HTMs. The Fourier‐transform infrared spectroscopy, X‐ray diffraction, and X‐ray photoelectron spectroscopy spectra of MAPbI₃ and DBTMT–MAPbI₃ films demonstrate that there is an interaction between DBTMT and MAPbI₃ at the interface through the sulfur atoms in DBTMT to passivate the defects, which is corresponding to the higher FF and PCE of the corresponding device.

A method of combined electron transporting bilayer is reported to reduce energy loss and inhibit defects in the perovskite solar cells (PSCs) by combining the commercially accessible SnO₂ and home‐made TiO₂ nanoparticles. Consequently, the PSCs devices acquire a high efficiency of 20.50%, which is superior to that based on SnO₂ layers with a efficiency of 18.09%.

Herein, commercially accessible SnO₂ and home‐made TiO₂ nanoparticles as a combined electron transporting bilayer (ETBL) are applied to achieve highly efficient planar perovskite solar cells (PSCs). With the formed cascade‐aligned energy levels from the proper stacking of SnO₂ and TiO₂ layers and the excellent defect‐passivation ability of TiO₂, SnO₂/TiO₂ ETBLs effectively reduce energy loss and inhibit defects formation both at the electron transporting layers (ETL)/perovskite interfaces and within the bulk of perovskite layer as revealed by a comprehensive analysis of photoelectric characteristic analysis, including ultraviolet photoelectron spectroscopy, photoluminescence, and electrochemical impedance spectroscopy. Consequently, the PSC devices acquired a power conversion efficiency (PCE) of 20.50% with a V _oc of 1.10 V, a J _sc of 24.2 mA cm⁻² and an fill factor of 77%, which are superior to the values of the control device based on single SnO₂ layer with a PCE of 18.09% (a 13.3% boosting on PCE). Moreover, there was no degradation after 49 days, indicating the great stability after adding TiO₂ layer. Herein, it is demonstrated that the cascaded alignment of energy levels between the electrode and perovskite layer by ETBLs could be an effective approach to improve the photovoltaic performance of the PSCs with excellent long‐term stability.

A hybrid electron transport layer (ETL) of SnO₂ and carbon nanotubes (CNTs) is designed by simple thermal decomposition of a mixed solution of SnCl₄·5H₂O and pretreated CNTs. Based on the hybrid ETL, a high efficiency of 20.33% is achieved in the hysteresis‐free perovskite solar cell, which shows 13.58% enhancement compared with the conventional device (power conversion efficiency = 17.90%).

Tin oxide (SnO₂) has recently received increasing attention as an electron transport layer (ETL) in planar perovskite solar cells (PSCs) and is considered a possible alternative to titanium oxide (TiO₂). However, planar devices based on pure solution‐processed SnO₂ ETL still have hysteresis, which greatly limits the application of SnO₂ in high‐efficiency solar cells. Herein, to address this issue, a hybrid ETL of SnO₂ and carbon nanotubes (CNTs) is fabricated by a simple thermal decomposing of a mixed solution of SnCl₄·5H₂O and pretreated CNTs (termed SnO₂–CNT). The addition of CNTs can significantly improve the conductivity of SnO₂ films and reduce the trap‐state density of SnO₂ films, which benefit carrier transfer from the perovskite layer to the cathode. As a result, a high efficiency of 20.33% is achieved in the hysteresis‐free PSCs based on SnO₂–CNT ETL, which shows 13.58% enhancement compared with the conventional device (power conversion efficiency = 17.90%).

Herein, a facile method is provided to fabricate the CsPbIBr₂ inorganic perovskite solar cells under low temperatures. The ZnO electron transport layer modification and band‐alignment engineering contribute to the outstanding power conversion efficiency of 10.16%, representing the highest efficiency for CsPbIBr₂ when the fabrication temperature is lower than 160 °C.

Recently, the thermally stable and facilely fabricated inorganic CsPbIBr₂ perovskite solar cells (PSCs) have attracted tremendous attention where the electron transport layer (ETL) is vital. However, the typical sintering temperature for the widely used electron transport material, that is, TiO₂, is more than 400 °C, elevating the cost and hindering the application. Due to high electron mobility and low fabrication temperature, ZnO becomes a desirable alternative for TiO₂, as the ETL in CsPbIBr₂ PSCs, albeit with low open‐circuit voltage (V _oc). Herein, this work introduces a trace of NH₄Cl to the sol–gel‐derived ZnO precursor to decrease the work function of the ZnO film, tune the surface morphology of the perovskite film, and thus suppress the density of trap states in the CsPbIBr₂ films. Consequently, full‐coverage and pure‐phase CsPbIBr₂ films consisting of micron‐size and high‐crystallinity grains are obtained. More importantly, for the optimal NH₄Cl‐modified ZnO, a shining improvement in V _oc from 1.08 to 1.27 V boosts the champion CsPbIBr₂ PSCs to obtain a power conversion efficiency of 10.16%, which is the highest value reported among pure‐CsPbIBr₂ PSCs under a low fabrication temperature of 160 °C. In addition, the NH₄Cl‐modified ZnO ETL reduces the severe hysteresis and increases the device stability significantly.

Organic photovoltaic (OPV) cells promise to have a good photovoltaic performance under the indoor light environment. Via optimizing the active layers, 1 cm² OPV cells are fabricated and a top power conversion efficiency of 22% under 1000 lux illumination is demonstrated.

Abstract

Organic photovoltaic (OPV) technologies have the advantages of fabricating larger‐area and light‐weight solar panels on flexible substrates by low‐cost roll‐to‐toll production. Recently, OPV cells have achieved many significant advances with power conversion efficiency (PCE) increasing rapidly. However, large‐scale solar farms using OPV modules still face great challenges, such as device stability. Herein, the applications of OPV cells in indoor light environments are studied. Via optimizing the active layers to have a good match with the indoor light source, 1 cm² OPV cells are fabricated and a top PCE of 22% under 1000 lux light‐emitting diode (2700 K) illumination is demonstrated. In this work, the light intensities are measured carefully. Incorporated with the external quantum efficiency and photon flux spectrum, the integral current densities of the cells are calculated to confirm the reliability of the photovoltaic measurement. In addition, the devices show much better stability under continuous indoor light illumination. The results suggest that designing wide‐bandgap active materials to meet the requirements for the indoor OPV cells has a great potential in achieving higher photovoltaic performance.

Application of the proposed slow post‐annealing for layered 2D perovskite solar cells based on BA₂MA₃Pb₄I₁₃ photo‐absorber leads to a favorable alignment on the multi‐perovskite phases and resultant champion power conversion efficiency to 17.26%, showing simultaneously enhanced open‐circuit voltage and short‐circuit current.

Abstract

Layered Ruddlesden–Popper (RP) phase (2D) halide perovskites have attracted tremendous attention due to the wide tunability on their optoelectronic properties and excellent robustness in photovoltaic devices. However, charge extraction/transport and ultimate power conversion efficiency (PCE) in 2D perovskite solar cells (PSCs) are still limited by the non‐eliminable quantum well effect. Here, a slow post‐annealing (SPA) process is proposed for BA₂MA₃Pb₄I₁₃ (n = 4) 2D PSCs by which a champion PCE of 17.26% is achieved with simultaneously enhanced open‐circuit voltage, short‐circuit current, and fill factor. Investigation with optical spectroscopy coupled with structural analyses indicates that enhanced crystal orientation and favorable alignment on the multiple perovskite phases (from the 2D phase near bottom to quasi‐3D phase near top regions) is obtained with SPA treatment, which promotes carrier transport/extraction and suppresses Shockley–Read–Hall charge recombination in the solar cell. As far as it is known, the reported PCE is so far the highest efficiency in RP phase 2D PSCs based on butylamine (BA) spacers (n = 4). The SPA‐processed devices exhibit a satisfactory stability with <4.5% degradation after 2000 h under N₂ environment without encapsulation. The demonstrated process strategy offers a promising route to push forward the performance in 2D PSCs toward realistic photovoltaic applications.

The spintronic properties of different hybrid organic–inorganic perovskites (HOIPs) are studied in spin valve devices, including spin diffusion length and spin lifetime, as well as the impact of the chemical components on these properties. This study aims at demonstrating promising spintronic applications of HOIPs, and providing a clear path for engineering spintronic devices based on HOIPs.

Abstract

The hybrid organic–inorganic perovskites (HOIPs) form a new class of semiconductors which show promising optoelectronic device applications. Remarkably, the optoelectronic properties of HOIP are tunable by changing the chemical components of their building blocks. Recently, the HOIP spintronic properties and their applications in spintronic devices have attracted substantial interest. Here the impact of the chemical component diversity in HOIPs on their spintronic properties is studied. Spin valve devices based on HOIPs with different organic cations and halogen atoms are fabricated. The spin diffusion length is obtained in the various HOIPs by measuring the giant magnetoresistance (GMR) response in spin valve devices with different perovskite interlayer thicknesses. In addition spin lifetime is also measured from the Hanle response. It is found that the spintronic properties of HOIPs are mainly determined by the halogen atoms, rather than the organic cations. The study provides a clear avenue for engineering spintronic devices based on HOIPs.

The elastic modulus of 3D perovskite is very close to that of human bones and the elastic modulus of 2D perovskite with long chains is close to that of cartilage. By reconstructing a crystal lattice with different A cations at the surface of perovskite films, a nature “bone‐joint” configuration is built in perovskite, which provides a cushioning effect to external stresses.

Abstract

To improve the photovoltaic performance (both efficiency and stability) in hybrid organic–inorganic halide perovskite solar cells, perovskite lattice distortion is investigated with regards to residual stress (and strain) in the polycrystalline thin films. It is revealed that residual stress is concentrated at the surface of the as‐prepared film, and an efficient method is further developed to release this interfacial stress by A site cation alloying. This results in lattice reconstruction at the surface of polycrystalline thin films, which in turn results in low elastic modulus. Thus, a “bone‐joint” configuration is constructed within the interface between the absorber and the carrier transport layer, which improves device performance substantially. The resultant photovoltaic devices exhibit an efficiency of 21.48% with good humidity stability and improved resistance against thermal cycling.

The OH…I⁻ hydrogen bonding interactions between poly(vinyl alcohol) (PVA) and FASnI₃ have the effects of introducing nucleation sites, slowing down crystal growth, directing the crystal orientation, reducing the trap states, and suppressing the migration of the ions. By adding PVA, the FASnI₃–PVA perovskite solar cells attain improved power conversion efficiency and stability.

Abstract

Tin‐based perovskites with narrow bandgaps and high charge‐carrier mobilities are promising candidates for the preparation of efficient lead‐free perovskite solar cells (PSCs). However, the crystalline rate of tin‐based perovskites is much faster, leading to abundant trap states and much lower open‐circuit voltage (V _oc). Here, hydrogen bonding is introduced to retard the crystalline rate of the FASnI₃ perovskite. By adding poly(vinyl alcohol) (PVA), the OH…I⁻ hydrogen bonding interactions between PVA and FASnI₃ have the effects of introducing nucleation sites, slowing down the crystal growth, directing the crystal orientation, reducing the trap states, and suppressing the migration of the iodide ions. In the presence of the PVA additive, the FASnI₃–PVA PSCs attain higher power conversion efficiency of 8.9% under a reverse scan with significantly improved V _oc from 0.55 to 0.63 V, which is one of the highest V _oc values for FASnI₃‐based PSCs. More importantly, the FASnI₃–PVA PSCs exhibit striking long‐term stability, with no decay in efficiency after 400 h of operation at the maximum power point. This approach, which makes use of the OH…I⁻ hydrogen bonding interactions between PVA and FASnI₃, is generally applicable for improving the efficiency and stability of the FASnI₃‐based PSCs.

A general approach for lab‐to‐manufacturing translation is developed to achieve high‐performance flexible organic solar modules without obvious efficiency loss. The shear impulse during the coating/printing process is applied to control the morphology evolution of the bulk heterojunction layer for both fullerene and nonfullerene acceptor systems. A quantitative transformation factor of shear impulse between slot‐die printing and spin‐coating is detected.

Abstract

The blossoming of organic solar cells (OSCs) has triggered enormous commercial applications, due to their high‐efficiency, light weight, and flexibility. However, the lab‐to‐manufacturing translation of the praisable performance from lab‐scale devices to industrial‐scale modules is still the Achilles' heel of OSCs. In fact, it is urgent to explore the mechanism of morphological evolution in the bulk heterojunction (BHJ) with different coating/printing methods. Here, a general approach to upscale flexible organic photovoltaics to module scale without obvious efficiency loss is demonstrated. The shear impulse during the coating/printing process is first applied to control the morphology evolution of the BHJ layer for both fullerene and nonfullerene acceptor systems. A quantitative transformation factor of shear impulse between slot‐die printing and spin‐coating is detected. Compelling results of morphological evolution, molecular stacking, and coarse‐grained molecular simulation verify the validity of the impulse translation. Accordingly, the efficiency of flexible devices via slot‐die printing achieves 9.10% for PTB7‐Th:PC₇₁BM and 9.77% for PBDB‐T:ITIC based on 1.04 cm² . Furthermore, 15 cm² flexible modules with effective efficiency up to 7.58% (PTB7‐Th:PC₇₁BM) and 8.90% (PBDB‐T:ITIC) are demonstrated with satisfying mechanical flexibility and operating stability. More importantly, this work outlines the shear impulse translation for organic printing electronics.

A high power conversion efficiency of 11.76%, the best efficiency for all‐polymer solar cells, is achieved by printing fabrication based on PTzBI‐Si:N2200 processing with 2‐methyltetrahydrofuran. A Multi‐length‐scaled morphology is found in the bulk heterojunctions, which ensures fast transfer of carriers and facilitates exciton separation, and boosts carrier mobility and current density, thus improving the device performance.

Abstract

All‐polymer solar cells (all‐PSCs) exhibit excellent stability and readily tunable ink viscosity, and are therefore especially suitable for printing preparation of large‐scale devices. At present, the efficiency of state‐of‐the‐art all‐PSCs fabricated by the spin‐coating method has exceeded 11%, laying the foundation for the preparation and practical utilization of printed devices. A high power conversion efficiency (PCE) of 11.76% is achieved based on PTzBI‐Si:N2200 all‐PSCs processing with 2‐methyltetrahydrofuran (MTHF, an environmentally friendly solvent) and preparation of active layers by slot die printing, which is the top efficient for all‐PSCs. Conversely, the PCE of devices processed by high‐boiling point chlorobenzene is less than 2%. Through the study of film formation kinetics, volatile solvents can freeze the morphology in a short time, and a more rigid conformation with strong intermolecular interaction combined with the solubility limit of PTzBI‐Si and N2200 in MTHF results in the formation of a fibril network in the bulk heterojunction. The multilength scaled morphology ensures fast transfer of carriers and facilitates exciton separation, which boosts carrier mobility and current density, thus improving the device performance. These results are of great significance for large‐scale printing fabrication of high‐efficiency all‐PSCs in the future.