Search

Methylammonium chloride (MACl) additive is almost irreplaceable in high‐performance formamidine perovskite photovoltaics. Nevertheless, Some of the problems that can arise from adding MACl are rarely mentioned. Herein, it is proposed for the first time that the addition of MACl would cause the non‐stoichiometric ratio in the perovskite film, resulting in the halogen vacancy. It is demonstrated that the non‐synchronous volatilization of methylamine cations and chloride ions leads to the formation of halogen vacancy defects. To solve this problem, the NH4HCOO is introduced into the perovskite precursor solution to passivate the halogen vacancy. The HCOO− ions have a strong force with lead ions and can fill the halogen vacancy defects. Consequently, the champion devices' power conversion efficiency (PCE) can be improved from 21.23% to 23.72% with negligible hysteresis. And the unencapsulated device can still retain >90% of the initial PCE even operating in N2 atmosphere for over 1200 h. This work illustrates another halogen defect source in the MACl‐assisted formamidine perovskite photovoltaics and provides a new route to obtain high‐performance perovskite solar cells. [ABSTRACT FROM AUTHOR]

The perovskite photovoltaic field has developed rapidly within a decade. In particular, formamidinium (FA)‐rich perovskite allows a broad absorption spectrum, and is considered to be one of the most promising perovskite materials. Great progress has been achieved, and most recorded high‐efficient perovskite solar cells (PSCs) used the FA‐rich perovskite light absorption layer. However, the black α‐phase formamidinium lead iodide (FAPbI3) perovskite easily transforms into an undesirable δ‐phase at a low temperature. Thus, researchers have put a lot of effort into deeply understanding the phase transformation and stabilization mechanism of FA‐rich perovskite. Herein, the fundamental physical properties of FAPbI3 materials, including crystal structure, phase‐transition temperature, charge‐carrier dynamics, etc. are summarized, and establish a complete phase evolution with temperature by reviewing previous reports. The intrinsic and external factors are subsequently discussed for influencing the stability of FAPbI3 perovskite and the remarkable breakthroughs of FA‐rich PSCs in recent years are reviewed. Moreover, a series of strategies to stabilize FA‐rich perovskite is summarized, including but not limited to compositional engineering, passivating engineering, processing engineering, and strain engineering. Finally, several new viewpoints are provided for improving the efficiency and stability of PSCs. This review may be regarded as a reference project for preparing high‐efficient and stable perovskite photovoltaic devices. [ABSTRACT FROM AUTHOR]

• NC 70 BA plays a dominant role in the photocurrent generating and charge transport. • The separation of exciton of NCBDT-4Cl mainly occurs on the NCBDT-4Cl/NC 70 BA interface. • The OSCs based on NC 70 BA exhibit a significant increase of 10% in PCE. • The shallower energy levels and better compatibility for double side chain fullerene derivative NC 70 BA than single side chain fullerene PC 71 BM. In this study, ternary organic solar cells (OSCs) are fabricated with the PBDB-T-2F as a polymer donor and NCBDT-4Cl as a fullerene-free acceptor, double side chain fullerene derivative NC 70 BA as a third component material and single side chain fullerene PC 71 BM as reference third component materials. The NC 70 BA-based ternary OSCs exhibit the highest PCE of 13.82%, which is 10% higher than that of PBDB-T-2F:NCBDT-4Cl binary OSCs and slightly higher than PC 71 BM-based ternary OSCs (13.24%). Detailed studies suggest that the shallow LUMO levels and double side chain for NC 70 BA is beneficial to broaden energy bandgap and improve compatibility, which is enhancing J SC and FF value. This work suggests that double side chain fullerene derivative NC 70 BA as third component materials is a promising way to finely tune the detailed photovoltaic parameters and further improve the photovoltaic performance of OSCs. [ABSTRACT FROM AUTHOR]

We prepared ternary organic solar cells (OSCs) by incorporating the medium wavelength absorption polymer PSEHTT into the PM6:L8-BO binary system. The power conversion efficiency (PCE) is improved from 15.83% to 16.66%. Although the fill factor (FF) is slightly reduced, the short-circuit current density (JSC) and open-circuit voltage (VOC) are significantly increased at the same time. A small amount of PSEHTT has a broad absorption spectrum in the short wavelength region and has good compatibility with PM6, which is conducive to fine-tuning the photon collection and improving the JSC. In addition, the highest occupied molecular orbital (HOMO) energy level of PSEHTT is deeper than that of PM6, which broadens the optical bandgap. This study provides an effective method to fabricate high-performance ternary OSCs by using a lower concentration of PSEHTT with PM6 as a hybrid donor material, which ensures a better surface and bulk morphology, improves photon collection, and broadens the optical bandgap. [ABSTRACT FROM AUTHOR]

[Display omitted] • Ternary PSCs were fabricated with PBDB-TF as third component materials. • The improvement of charge dynamics process of ternary photoactive layer by ternary strategy. • The improved exciton-dissociation at the donor–blend acceptor interface. In this manuscripts, a ternary polymer solar cells (PSCs) are fabricate with two "D18-series" donor (D18-Cl and D18) as blend donor and T6 as acceptor. The effects of D18-Cl and D18 in ternary PSC on the film morphology, photoelectronic properties and charge carrier dynamics were systematically investigated. By finely adjusting the D18 content, a power conversion efficiency (PCE) of 16.66 % is achieved in the optimized ternary PSCs with 35 wt% D18 in donor, resulting from significantly improved short-circuit-current density (J SC) of 26.80 mA cm−2 in comparison with those of D18-Cl:Y6 binary PSCs. The J SC of ternary PSCs monotonously increase along with the incorporation of D18, indicating that D18 is comprehensively optimal short wavelength photon harvesting compared with D18-Cl. Both D18-Cl and D18 are shown similar highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) energy levels, which is beneficial to efficient charge transport at the blend donor domain. Our work indicates that the blend of D18-Cl and D18 as blend donor and Y6 as electron acceptor to boost photovoltaic performance in the ternary PSCs. [ABSTRACT FROM AUTHOR]

In this paper, ternary polymer solar cells (PSCs) consisting of two blend donors (FTAZ and PTB7-Th) and one acceptor (N3) with similar highest occupied molecular orbital (HOMO) energy levels, different absorption peaks and cascading lowest unoccupied molecular orbital (LUMO) energy levels are built. The ternary PSCs achieve higher photovoltaic performance and better thermal stability compared to the FTAZ:N3 binary PSCs. The A medium wavelength absorption FTAZ polymers and long wavelength absorption PTB7-Th polymers as the blend donor, and near-infrared wavelength absorption N3 as the acceptor. The optimize ternary PSCs exhibit a maximum power conversion efficiency of 15.65%, with an open-circuit voltage of 0.852 V, a short-circuit current of 25.25 mA cm − 2, and an FF of 72.5%. This performance of device is attributed to more efficient exciton dissociation and suppression of charge recombination within ternary films. The ternary PSCs also show good crystallinity and surface morphology at room temperature and after thermal annealing for 20 h at 70 °C, which is attribute to the better thermal stability of the ternary PSCs. • Ternary PSCs were fabricated with PTB7-Th as third component materials. • The improvement of charge dynamics process of ternary photoactive layer by ternary strategy. • The improved exciton-dissociation at the donor–blend acceptor interface. [ABSTRACT FROM AUTHOR]

Photo-annealing treatment has successfully been demonstrated in organic solar cells (OSCs) with solution-processable titanium (diisopropoxide) bis(2,4-pentanedionate) (TIPD) as an electron extraction layer; this process was shown without thermal annealing treatment. The power conversion efficiency (PCE) is quite low in the initial stage, though it dramatically increases following constant light illumination and reaches a saturated state after 9 min of light illumination. X-ray photoelectron spectroscopy (XPS), Fourier transform infrared (FTIR) and ultraviolet photoemission spectroscopy (UPS) were used, and they showed that the TIPD molecules decomposed and formed stable Ti O bonds. According to photocurrent density-effective voltage curve (J ph - V eff), short-circuit current density (J SC) and open-circuit voltage (V OC) value under different light intensity, the photo-annealed TIPD-based OSCs showed efficient charge transport and suppressed charge recombination. Thus, after a fresh TIPD solution was spin-coated onto the indium tin oxide (ITO) surface and photo-annealed for 9 min, the OSCs showed the highest photovoltaic performance compared to ZnO-based OSCs. [Display omitted] [ABSTRACT FROM AUTHOR]

Photo-annealing treatment titanium chelate (TIPD) layer, which was the indium tin oxide (ITO) interface-modified layer, was used as a replacement for the thermal annealing treatment of TIPD. The power conversion efficiency (PCE) of photo-annealed TIPD-based polymer solar cells (PSCs) is quite low in the initial stage, but it dramatically increases following constant light illumination, and the cell achieves a saturated state after 9 min of light illumination. By employing the mixed films poly[1-(5-(4,8-bis(5-(2-ethylhexyl)-4-fluorothiophen-2-yl)-6-methylbenzo[1,2-b:4,5-b′]dithiophen-2-yl)thiophen-2-yl)-5,7-bis(2-ethylhexyl)-3-(5-methylthiophen-2-yl)-4H,8H-benzo[1,2-c:4,5-c′]dithiophene-4,8-dione] (PBDB-TF) and 2,2′-((2 Z ,2′ Z)-(((4,4,9,9-tetrakis-(4-hexylphenyl)-4,9-dihydro-sindaceno[1,2- b :5,6- b ']-dithiophene-2,7-diyl)bis(4-((2-ethylhexyl)oxy)thiophene-5,2-diyl))bis(methanylylidene))bis(5,6-difluoro-3-oxo-2,3-dihydro-1H-indene-2,1-diylidene)) dimalononitrile (IEICO-4F) as photoactive layers, we improved the photovoltaic performance. The enhanced photovoltaic performance of TIPD films treated with photo-annealing was explained by the increased short-circuit current density (J SC). Efficient medium- and long-wavelength light transmittance and suppression of charge recombination are beneficial for enhancing the J SC value. • Titanium chelate (TIPD) films by photo annealing treatment is efficient electron extraction layer (EEL) material. • The photo annealing treatment TIPD films achieve efficient charge transport and weak charge recombination. • The efficient medium and long wavelength light transmittance efficiency for photo annealing TIPD films. [ABSTRACT FROM AUTHOR]

In this study, a ternary polymer solar cell (PSCs) are fabricated by using two well-compatible donors as a blend donor (D18 as the host donor and PBDB-TF as the guest donor) and Y6 as an acceptor. The D18:Y6 and PBDB-TF:Y6 binary PSCs exhibit 13.96% and 13.42% power conversion efficiencies (PCEs), respectively. D18 and PBDB-TF have similar highest occupied molecular orbital (HOMO) energy levels, which prevents the formation of charge recombination centers within photoactive layer. The increased short-circuit current density (J SC) is mainly attributed to the complementary absorption spectra of PBDB-TF to that of D18 and Y6. In addition, the cascade lowest unoccupied molecular orbital (LUMO) energy levels of D18 and PBDB-TF lead to improved exciton dissociation and charge transport at the D18/PBDB-TF interface. The optimized ternary PSCs show highest PCE of 14.85%. Such ternary strategy with two well-compatible donors with similar HOMO energy levels and cascade LUMO energy levels is an efficient method to realize performance improvement of PSCs. [Display omitted] • Ternary PSCs were fabricated with PBDB-TF as third component materials. • The improvement of charge dynamics process by ternary strategy. • The improved exciton-dissociation at the donor–blend acceptor interface. • The ternary PSCs with blend donor achieved a PCE of 14.85%. [ABSTRACT FROM AUTHOR]

Photocatalytic overall water splitting (POWS) is a promising route for converting solar energy into green and sustainable energy. Herein, we report a facile hydrothermal approach to fabricate polyhedron BiVO4 by Mo and Yco-doping (MYB) photocatalysts with suitable band gap for POWS. The MYB exhibited enhanced visible light-driven POWS activities in comparison with that of as-prepared BiVO4, Y-BiVO4 and M-BiVO4, with the maximum H2 and O2 evolution rate of 34.7 and 17.4 μmol·h−1·g−1, respectively. The optimum activity of the catalyst was controlled by adjusting Mo content of MYB. The photodeposition of Pt shows that there are special separation reduction and oxidation centers on the surface of MYB. Electrochemical experiments further confirmed the enhanced charge separation of MYB. MYB photocatalyst has small particle size, unique polyhedral structure, large specific surface area and high (103) and (200) surface exposure, thus improving POWS performance, high electron transfer efficiency and effective separation of photogenerated electron–hole pairs. Because of the doping of Mo and Y elements, the electronic structure of the catalyst is altered, enhancing light absorption and reducing the recombination of photogenerated electron–hole pair. The current study revealed that the MYB products could serve as cost-effective and stable photocatalysts for POWS. [ABSTRACT FROM AUTHOR]

Wide‐bandgap CsPbCl3 perovskite has fueled studies on applications in a variety of newly developing optoelectronic devices, including solar cells, lasers, light‐emitting diodes, and photodetectors. Most of them are now focused on film fabrication and device performance optimization, technology transfer of these proof‐of‐concept devices to the market will necessitate optimization of the device structure to minimize the optical loss and fabrication cost. While device model‐based electro‐optics simulations are considered a powerful method to attain the purpose, during which accurate optical constants are preconditions. Herein, for the first time, the optical constants of CsPbCl3 film through Mueller matrix spectroscopic ellipsometry (SE) are reported. Taking optoelectronic devices in vertical structure as a demonstration, simulations on the distributions of 2D electromagnetic field and photo‐generated electron field are arranged, successfully demonstrating the profile of the photons and electrons inside the devices. The evolution trend of device performance in the experiments matched with the simulations, for device performance is closely related to the photons and photo‐generated electrons. Benefitting from the simulations and experiments, general design criteria of the CsPbCl3‐based optoelectronic and photonic devices are posed, inevitably accelerating their development and commercialization. [ABSTRACT FROM AUTHOR]

α-Formamidinium lead iodide (α-FAPbI 3) has become one of the most promising candidate materials for stable perovskite solar cells (PSCs) owing to their outstanding optoelectronic properties and high thermal stability. The crystallinity of the active layer of perovskite is essential to the performance of perovskite solar cells. In this paper, we added lead acetate Pb(Ac) 2 as a grain growth agent into the perovskite precursor solution to prepare high-efficiency and stable perovskite solar cells. It was revealed that the crystals of Pb(Ac) 2 -modified film grew selectively along the [200] direction and that the FAPbI 3 active layer grains were arranged neatly and densely, due to the significant influence of a moderate amount of weakly acidic Ac- on the crystal growth of FAPbI 3. The relative reduction in its grain boundaries led to the decrease in the grain boundary impedance, and it was easier for electrons to perform long-range migration in the perovskite active layer. The beneficial effects of Pb(Ac) 2 were further expiored by femtosecond Fs-TA measurements and density of states (tDOS) analysis, where the carrier lifetimes τ 2 was increased from 482.4 ps to 1340 ps, and the trap density of film states was significantly reduced. The filling factor (FF) and power conversion efficiency (PCE) were increased from 76.5% and 19.7–81.1% and 21.8%, respectively, the Pb(Ac) 2 devices were placed in air for 800 h for the light aging test, and the test results still maintained 90% of the original efficiency, which improved the stability of FAPbI 3 crystals. • Pb(Ac) 2 as an additive to modulate the crystalline quality of perovskite active layer films. • Perovskite solar cell defect reduction and carrier lifetime increase by Pb(Ac) 2 modification. • The Pb(Ac) 2 -modified active layer grains have preferential orientation and orderly arrangement. • 81.1% filling factor and 21.8% efficiency are achieved for a single PSC cell with excellent stability. [ABSTRACT FROM AUTHOR]

The development of perovskite solar cells has improved rapidly. However, PSCs generally suffer from instability, due to the detrimental defects. Additive engineering is a favorable method for defect passivation. In this work, the linear pseudo-halogen salt, KSCN, is introduced into the MAPbI 3 perovskite film to improve the performance of PSC. The trap density of cells with SCN− is decreased significantly. The SCN− not only can fill halogen vacancies to reduce the halide-related defects, but also can interact with the uncoordinated Pb2+ via coordinate bond to stabilize perovskite lattice structure. Moreover, the performance of devices with other linear pseudo-halogen anions (OCN−, SeCN−) are also investigated. Due to the improved short circuit current density, the power conversion efficiency of devices increases from 18.02% (PVK) to 20.41% (PVK–SCN-), 19.53% (PVK–OCN-) and 19.23% (PVK–SeCN-), respectively. After introducing pseudo-halide anions, the devices showed robust stability under the ambient environment. [ABSTRACT FROM AUTHOR]

Organic-inorganic hybrid perovskite materials with distinctive optoelectronic properties have attracted much interest in the field of solar cells. As the light absorber, the quality of perovskite films is crucial to the performances of perovskite solar cells. Anti-solvent engineering seems to be an efficient method in preparing high-quality perovskite films, but mostly used anti-solvents are toxic, such as chlorobenzene (CB)， which is harmful to the environmental protection. In the present work, we used the green anti-solvent diethyl carbonate (DEC) instead of CB, demonstrated that the DEC engineered CH 3 NH 3 PbI 3 film exhibits improved morphology and crystallinity as well as reducing defects, which can be attributed to the interaction between DEC and the solvent dimethyl sulfoxide (DMSO). The DEC anti-solvent assisting yields efficient CH 3 NH 3 PbI 3 perovskite solar cells with a champion power conversion efficiency of 20.20% and a steady state efficiency of 86% over a period of 20 days of storage under ambient conditions. The present study provides a viable path way to design green and effective perovskite solar cells in the future. [Display omitted] • Developed a green solvent-assisted perovskite crystallization method. • Formed uniform and compact perovskite films with large grains. • High-quality perovskite films prepared by green anti-solvent diethyl carbonate. [ABSTRACT FROM AUTHOR]