The optimization of intermediate semi-bonding structure using solvent vapor annealing for high performance p-i-n structure perovskite solar cells

The high quality perovskite film construction is the most crucial factor for the high performance perovskite solar cells. Solvent vaopr annelaing (SVA) is one of the best method to achieve the high quality perovkite film. We have fully compared the various high boiling point aprotic solvents N,N-dimethylformamide (DMF), Dimethyl sulfoxide (DMSO) and 1-Methyl-2-pyrrolidone (NMP) for SVA effect for perovskite solar cells. By optimizing temperature and time of SVA, vertically growthed high quality perovskite film via intermediate phase of PbI2-NMP structure was achieved which induces high performance of device. PbI2-NMP intermediate phase of perovskite film can be attributed to pinhole-free, longer carrier lifetime, and oxygen state free. The optimized device with NMP SVA treatment achieved 15.71% of PCE compared to without SVA treatment 7.85% of PCE

Coordination modulated passivation for stable organic-inorganic perovskite solar cells

Despite the recent exceptional rise in power conversion efficiency of perovskite solar cells (PSCs), surface defects and ion migration related instability are still present in PSCs. The chain length and binding energy of the passivation material play important roles in defect passivation, ion migration, moisture stability, and device-performance improvement. We synthesized three sulfonated ammonium compounds and investigated the ef-fect of post-passivation with these compounds on ion-migration and stability. New materials with high binding energy include octylamine (OA) functionalized with sulfanilic acid (OAS), p-toluenesulfonic acid (OAT), and camphorsulfonic acid (OAC). The passivation improves power conversion efficiency (PCE) from 21.06% for the control to 24.37% for the devices treated with OAC. The champion device's hysteresis index decreased to 0.01 compared to 0.11 for the control device, which is the lowest reported so far. Furthermore, the passivated perovskite films retain over 85% of their initial PCE under 60% relative humidity for 1,600 h, and the device with OAC maintains over 90% of its initial operational long-term device stability without encapsulation for 600 h under 1 sun-illumination

Highly Stable Bulk Perovskite for Blue LEDs with Anion-Exchange Method

To date, the light emitting diode (LED) based halide perovskite was rapidly developed due to the outstanding property of perovskite materials. However, the blue perovskite LEDs based on the bulk halide perovskites have been rarely researched and showed low efficiencies. The bulk blue perovskite LEDs suffered from insufficient coverage on the substrate due to the low solubility of the inorganic Cl sources or damaged by the structural instability with participation of organic cations. Here, we show the new method of fabricating stable inorganic bulk blue perovskite LEDs with the anion exchange approach to avoid use of insoluble Cl precursors. The devices showed nice operational spectral stability at the desired blue emission peak. The bulk perovskite blue LEDs showed a maximum luminance of 1468 and 494 cd m(-2) for the 490 and 470 nm emission peaks, respectively

Zn2+ ion doping for structural modulation of lead-free Sn-based perovskite solar cells

Sn-based perovskites have intrinsic defects, such as Sn vacancies, oxidised components (Sn4+), and local lattice strain in the perovskite crystalline structure. In this study, Zn metal powder (Zn-0) was introduced to reduce Sn oxidation in the solution step based on the redox potential difference. Additionally, Zn2+ was introduced in the perovskite precursor, which decreased the intrinsic defects and lattice strain of the perovskite films. The diffusion length, particularly that of the hole, increased with a reduction in the lattice strain, and Zn doping led to interfacial energy-level alignment of the perovskite and hole-transporting layers. The reduced lattice strain decreased the defect density and charge carrier recombination of perovskite devices. The power conversion efficiency of the Zn-doped Sn-based perovskite solar cell was improved to 11.39% compared to the 8.56% of the reference device

Controlling the formation energy of perovskite phase via surface polarity of substrate for efficient pure-blue light-emitting diodes

Quasi-two-dimensional (quasi-2D) perovskites are composed of self-organized multiple-quantum-well structures. Imbalanced crystallization during the solution-processed deposition results in the formation of different 2D phases, which are affected by the surface polarity of substrates. Herein, we investigate the influence of the surface polarity of the underlying hole injection layer (HIL) on the crystallization dynamics of each 2D phase and the luminescence properties of resulting quasi-2D perovskite films. Incorporating L-dopa involving hydroxyl groups into the HIL gives the substrate a higher surface polarity, allowing the decrease in the critical free energy of nucleation. This HIL ensures the formation of dense nuclei involving a small-sized nucleus, which enables the quasi-2D perovskite film to entail a lower-n-dominated phase distribution. The modulated phase distribution eventually induces a hypsochromically shifted luminescence spectrum. Furthermore, by controlling the ratio of L-phenylalanine and L-dopa, efficient perovskite light-emitting diodes (PeLEDs) having well-matched electronic structure and pure-blue perovskite emitter are realized with a maximum external quantum efficiency of 5.57% at 472 nm. This work provides a facile approach to achieving efficient pure-blue PeLEDs

Manipulated Interface for Enhanced Energy Cascade in Quasi-2D Blue Perovskite Light-Emitting Diodes

Quasi-two-dimensional (2D) perovskites have recently emerged as emitters in blue perovskite light-emitting diodes (PeLEDs). The cascading energy-transfer process between different 2D phases plays an essential role in the high performance of this class of PeLEDs. Herein, we propose an interfacial engineering strategy by incorporating a zwitterionic additive, l-phenylalanine, into the hole-injection layer (HIL), enabling suppression of trap-assisted deactivation channels by virtue of the coordination interactions between the additive and Pb2+ defects in the perovskite phase. In addition, the introduction of l-phenylalanine reduces the release of metallic indium species from indium tin oxide substrates initiated by acidic HILs, resulting in the suppression of luminescence quenching in the perovskite layer. The synergetic benefits create an ideal energy landscape, blocking energy losses and boosting PeLED performance with a peak external quantum efficiency of 10.98% at 480 nm and extended device lifetimes. Our approach provides a versatile strategy to achieve high-performance blue PeLEDs

Formate as Anti-Oxidation Additives for Pb-Free FASnI(3) Perovskite Solar Cells

Pb-free Sn-based perovskite solar cells (PSCs) have significant potential for application in photovoltaic devices because oftheir suitable bandgap, low exciton binding energy, high carrier mobility, and long diffusion length. However, their performance is hampered by several issues. Sn-based perovskites are highly susceptible to oxidation, which induces a high concentration of defects and degrades the chemical stability of the perovskite crystals. Herein, the anion formate (HCOO-) can effectively suppress the oxidation of Sn in the pure formamidinium tin triiodide (FASnI(3)) perovskite without using A-site cationic additives. Moreover, the presence of formate results in a uniform pinhole-free perovskite film with a low trap density, reduced charge carrier recombination, and improved charge extraction. Density functional theory calculations show that formate-treated FASnI(3) has improved stability against oxidative Sn degradation. The formate-treated PSC achieves a power conversion efficiency of 12.11% at a high open-circuit voltage of 0.71 V. The device exhibits improved stability in ambient air in which it maintained over 80% of its initial power conversion efficiency after 180 min because oxidation is inhibited owing to the strong interaction between Sn and formate

Pseudo-halide anion engineering for ??-FAPbI3 perovskite solar cells

Metal halide perovskites of the general formula ABX(3)-where A is a monovalent cation such as caesium, methylammonium or formamidinium; B is divalent lead, tin or germanium; and X is a halide anion-have shown great potential as light harvesters for thin-film photovoltaics(1-5). Among a large number of compositions investigated, the cubic alpha-phase of formamidinium lead triiodide (FAPbI(3)) has emerged as the most promising semiconductor for highly efficient and stable perovskite solar cells(6-9), and maximizing the performance of this material in such devices is of vital importance for the perovskite research community. Here we introduce an anion engineering concept that uses the pseudo-halide anion formate (HCOO-) to suppress anion-vacancy defects that are present at grain boundaries and at the surface of the perovskite films and to augment the crystallinity of the films. The resulting solar cell devices attain a power conversion efficiency of 25.6 per cent (certified 25.2 per cent), have long-term operational stability (450 hours) and show intense electroluminescence with external quantum efficiencies of more than 10 per cent. Our findings provide a direct route to eliminate the most abundant and deleterious lattice defects present in metal halide perovskites, providing a facile access to solution-processable films with improved optoelectronic performance