Photocurrent hysteresis related to ion motion in metal-organic perovskites

Improving device performance of MAPbI3photovoltaic cells by manipulating the crystal orientation of tetragonal perovskites

The properties of CH₃NH₃PbI₃(MAPbI₃) crystalline thin films and the device performance of highly efficient MAPbI₃photovoltaic cells are investigated by varying the temperature of the antisolvent from 20 °C to 50 °C during the washing enhanced nucleation (WEN) process. The surface, structural, optoelectronic and defect properties of the perovskite thin films are characterized through atomic-force microscopy, X-ray diffractometry and photoluminescence spectrometry. The experimental results show that changing the temperature of the antisolvent during the WEN process can manipulate the MAPbI₃crystalline thin films from the (110)-(002) complex phase to a (002) preferred phase. It is noted that the highest power conversion efficient of the inverted MAPbI₃photovoltaic cells is 19.30%, mainly due to the increased carrier collection efficiency and reduced carrier recombination when the temperature of the antisolvent is 30 °C.

Improvement of interfacial contact for efficient PCBM/MAPbI3planar heterojunction solar cells with a binary antisolvent mixture treatment

Atomic-force microscopic images, x-ray diffraction patterns, Urbach energies and photoluminescence quenching experiments show that the interfacial contact quality between the hydrophobic [6,6]-phenyl-C₆₁-buttric acid methyl ester (PCBM) thin film and hydrophilic CH₃NH₃PbI₃(MAPbI₃) thin film can be effectively improved by using a binary antisolvent mixture (toluene:dichloromethane or chlorobenzene:dichloromethane) in the anti-solvent mixture-mediated nucleation process, which increases the averaged power conversion efficiency of the resultant PEDOT:PSS (P3CT-Na) thin film based MAPbI₃solar cells from 13.18% (18.52%) to 13.80% (19.55%). Beside, the use of 10% dichloromethane (DCM) in the binary antisolvent mixture results in a nano-textured MAPbI₃thin film with multicrystalline micrometer-sized grains and thereby increasing the short-circuit current density and fill factor (FF) of the resultant solar cells. It is noted that a remarkable FF of 80.33% is achieved, which can be used to explain the stable photovoltaic performance without additional encapsulations.

Low photoactive phase temperature all-inorganic, tin-lead mixed perovskite solar cell

CsPbI₃ films have recently attracted significant attention as efficient absorbers for thermally stable photovoltaic devices. However, their large bandgap and photoactive black phase formation at high temperature impede their use for practical applications. Using the concept of lattice contraction, we demonstrate a low bandgap (≤1.44 eV) cesium-based inorganic perovskite CsPb_xSn_1−xI₃ that can be solution processed at low temperature for photovoltaic devices. The results from systematic measurements imply that the partial substitution of lead (Pb) with tin (Sn) results in crystal lattice contraction, which is essential for realizing photoactive phase formation at l00 °C and stabilizing photoactive phase at room temperature. These findings demonstrate the potential of using cesium-based inorganic perovskite as viable alternatives to MA- or FA-based perovskite photovoltaic materials.

In Cs-based all inorganic perovskite solar cells based, doping Sn can cause lattice shrinkage, which reduces annealing temperature of forming photoactive phase.

Black phosphorus quantum dots in inorganic perovskite thin films for efficient photovoltaic application

Black phosphorus quantum dots (BPQDs) are proposed as effective seed-like sites to modulate the nucleation and growth of CsPbI₂Br perovskite crystalline thin layers, allowing an enhanced crystallization and remarkable morphological improvement. We reveal that the lone-pair electrons of BPQDs can induce strong binding between molecules of the CsPbI₂Br precursor solution and phosphorus atoms stemming from the concomitant reduction in coulombic repulsion. The four-phase transition during the annealing process yields an α-phase CsPbI₂Br stabilized by BPQDs. The BPQDS/CsPbI₂Br core-shell structure concomitantly reinforces a stable CsPbI₂Br crystallite and suppresses the oxidation of BPQDs. Consequently, a power conversion efficiency of 15.47% can be achieved for 0.7 wt % BPQDs embedded in CsPbI₂Br film-based devices, with an enhanced cell stability, under ambient conditions. Our finding is a decisive step in the exploration of crystallization and phase stability that can lead to the realization of efficient and stable inorganic perovskite solar cells.

An in situ rewritable electrically-erasable photo-memory device for terahertz waves

A terahertz read-only in situ electrically-erasable rewritable photo-memory device based on a perovskite:Ag (perovskite with Ag nanoparticles added)/SnO₂/PEDOT:PSS hetero-junction structure is reported. Under low optical excitation, considerable terahertz amplitude modulation in a perovskite:Ag/PEDOT:PSS hybrid structure was achieved. When a SnO₂ nanoparticle film was inserted between the perovskite and PEDOT:PSS layer, the attenuation of the terahertz signal was weaker than that of the perovskite:Ag/PEDOT:PSS hybrid structure; however, the SnO₂ nanoparticle film considerably prolonged the recovery time of the modulated terahertz wave in air after photo-excitation was stopped. In addition, when bias voltages were applied to the perovskite:Ag/PEDOT:PSS and perovskite:Ag/SnO₂/PEDOT:PSS hybrid structures, respectively, the terahertz signals recovered rapidly for both structures. Consequently, the photo-memory functionality was achieved based on a perovskite:Ag/SnO₂/PEDOT:PSS hybrid structure with an in situ method for erasing stored information.

Will organic-inorganic hybrid halide lead perovskites be eliminated from optoelectronic applications?

In the development of perovskite solar cells, a new version of Don Quixote is needed if scientists are to keep on seeking the most celebrated works of literature, according to the evaluation criterion of 'THE FIRST' and 'THE BEST'. Perovskite solar cells have developed rapidly in recent years due to several factors, including their high light absorption capability, long carrier lifetime, high defect tolerance, and adjustable band gap. Since they were first reported in 2009, solar cells based on organic-inorganic hybrid halide lead perovskites have achieved a power conversion efficiency of over 23%. However, although there are broad development prospects for perovskite solar cells, their lead toxicity and instability resulting from the use of organic-inorganic hybrid halide lead perovskites such as CH₃NH₃PbI₃ limit their application, which is further deteriorating progressively. Therefore, the development of environmentally friendly, stable and efficient perovskite materials for future optoelectronic applications has long-term practical significance, which can eventually be commercialized. In this case, the discovery and development of inorganic lead-free perovskite light absorbing materials have become an active research topic in the field of photovoltaics. In this review, we discuss the application of organic-inorganic hybrid halide lead perovskites. This application is further analyzed and summarized using the research progress on inorganic lead-free perovskite solar cells by restoring some relevant prospects for the development of inorganic lead-free perovskite solar cells.