RESUMEN
Defects formed by halide ion escape and wettability of the perovskite absorber are essential limiting factors in achieving high performance of perovskite solar cells (PSCs). Herein, a series of ionic organic modulators are designed to contain halide anions to prevent defect formation and improve the surface tension of the perovskite absorber. It was found that the surface modulator containing Br anions is the most effective one due to its capability in bonding with the undercoordinated Pb2+ ions to reduce charge recombination. Moreover, this surface modulator effectively creates a suitable energy level between the perovskite and hole transport layer to promote carrier transfer. In addition, the surface modulator forms a chemisorbed capping layer on the perovskite surface to improve its hydrophobicity. As a result, the efficiency of PSCs based on surface modulators containing Br anion enhances to 23.32% from 21.08% of the control device. The efficiency of unencapsulated PSCs with a surface modulator retains 75.42% of its initial value under about 35% humidity stored in the air for 28 days, while the control device only maintained 44.49% of its initial efficiency. The excellent stability originates from the hydrophobic perovskite surface after capping the surface modulator.
RESUMEN
Most studies choose passivators essentially in a trial-and-error fashion in an attempt to attain high efficiency in perovskite solar cells (PSCs). Using deep-level transient spectroscopy (DLTS) measurements, the type of defects in perovskite films was determined to guide the passivator selection for PSCs. Three kinds of positively charged defects were found in the target PSC system. Fluorinated phenylethylamine hydroiodide (FPEAI) was chosen to passivate the surface defects due to the electronegativity and hydrophobicity of fluorine. Due to the decreased surface roughness, increased hydrophobicity, lowered defect density, and improved carrier dynamics as observed by ultrafast transient absorption spectroscopy (TAS), a PSC with meta-F-PEAI had the best efficiency over 23 % with open-circuit voltage of 1.155â V and fill factor of 80.15 %. In addition, the long-term stability of the PSC was significantly improved. The present work provides a new means to select the best passivator for different types of defects.
RESUMEN
Herein, ultrathin (â¼35 µm) CH3NH3PbI3 (MAPbI3) single-crystalline wafers have been successfully prepared by using an appropriate geometry-regulated dynamic-flow reaction system. The measurement results proved that the obtained wafers have high crystallinity, and showed broad light absorption from ultraviolet to near infrared (850 nm) which can be attributed to the indirect bandgap. Straight after, such an MAPbI3 wafer was used to fabricate high-quality photodetectors (PDs). On account of its faster carrier transport and significantly reduced defect density, the device exhibits a high photoresponse (R) of 5 A/W and short on/off response (0.039 s/0.017 s). Interestingly, by introducing a Cr interlayer between the MAPbI3 wafer and the Au electrode to avoid the migration of Au, the PD shows nearly no degradation when it works at 200 °C. Furthermore, the device performance shows very little degradation over the course of 60 days of storage under ambient conditions owing to its lack of grain boundaries. We believe the strategy reported here is very promising for achieving broad photodetection in a harsh environment.
RESUMEN
As the black cesium lead iodide (CsPbI3) tends to transit into a yellow δ-phase at ambient, it is imperative to develop a stabilized black phase for photovoltaic applications. Herein, we report a distorted black CsPbI3 film by exploiting the synergistic effect of hydroiodic acid (HI) and phenylethylammonium iodide (PEAI) additives. It is found that the HI induces formation of hydrogen lead iodide (HPbI3+x), an intermediate to the distorted black phase with appropriate band gap of 1.69 eV; while PEAI provides nucleation for optimized crystallization. More importantly, it stabilizes the distorted black phase by hindering phase transition via its steric effects. Upon optimization, we have attained solar cell efficiency as high as 15.07%. Specifically, the bare cell without any encapsulation shows negligible efficiency loss after 300 h of light soaking. The device keeps 92% of its initial cell efficiency after being stored for 2 months under ambient conditions.
RESUMEN
In the original version of this Article, the author name 'Shengzhong Liu' was incorrectly given as 'Liu Shengzhong'. This has been corrected in both the PDF and HTML versions of the Article.
RESUMEN
All-inorganic CsPbBr3 perovskite solar cells display outstanding stability toward moisture, light soaking, and thermal stressing, demonstrating great potential in tandem solar cells and toward commercialization. Unfortunately, it is still challenging to prepare high-performance CsPbBr3 films at moderate temperatures. Herein, a uniform, compact CsPbBr3 film was fabricated using its quantum dot (QD)-based ink precursor. The film was then treated using thiocyanate ethyl acetate (EA) solution in all-ambient conditions to produce a superior CsPbBr3-CsPb2Br5 composite film with a larger grain size and minimal defects. The achievement was attributed to the surface dissolution and recrystallization of the existing SCN- and EA. More specifically, the SCN- ions were first absorbed on the Pb atoms, leading to the dissolution and stripping of Cs+ and Br- ions from the CsPbBr3 QDs. On the other hand, the EA solution enhances the diffusion dynamics of surface atoms and the surfactant species. It is found that a small amount of CsPb2Br5 in the composite film gives the best surface passivation, while the Br-rich surface decreases Br vacancies (VBr) for a prolonged carrier lifetime. As a result, the fabricated device gives a higher solar cell efficiency of 6.81% with an outstanding long-term stability.
RESUMEN
Recently, inorganic CsPbI2Br perovskite is attracting ever-increasing attention for its outstanding optoelectronic properties and ambient phase stability. Here, an efficient CsPbI2Br perovskite solar cell (PSC) is developed by: 1) using a dimension-grading heterojunction based on a quantum dots (QDs)/bulk film structure, and 2) post-treatment of the CsPbI2Br QDs/film with organic iodine salt to form an ultrathin iodine-ion-enriched perovskite layer on the top of the perovskite film. It is found that the above procedures generate proper band edge bending for improved carrier collection, resulting in effectively decreased recombination loss and improved hole extraction efficiency. Meanwhile, the organic capping layer from the iodine salt also surrounds the QDs and tunes the surface chemistry for further improved charge transport at the interface. As a result, the champion device achieves long-term stabilized power conversion efficiency beyond 14%.