Environmental‐Friendly Urea Additive Induced Large Perovskite Grains for High Performance Inverted Solar Cells

Abstract

It is a challenge to grow perovskite films with large crystalline grains and a full coverage on the surface of an organic compound film by a solution process. Herein, we for the first time introduce environmental‐friendly urea into PbI2 precursor to mediate the perovskite film growth and crystallization on the top of PEODT:PSS for efficient inverted solar cells. This method attains high‐quality perovskite films with large‐size grains of over 2 μm and a full coverage. This enables us to fabricate the inverted perovskite solar cells showing a maximum efficiency of 18.01% with a fill factor of 82.29% and a stabilized efficiency of 17.56%. Infrared spectroscopy and scanning electron microscopy images demonstrate that urea is coordinated with PbI2 to form PbI2 · OC(NH2)2 complex, resulting in large PbI2 flakes by a slow crystallization. The large PbI2 flake with fewer nucleation sites is conducive to forming monolithic perovskite grains. Further investigation indicates that CH3NH3I · PbI2 · OC(NH2)2 complex is formed as an intermediate phase, which retards the crystallization process of the perovskite films. These factors lead to a high‐quality perovskite film with large grain size and excellent crystallinity.

Studies of Graphdiyne‐ZnO Nanocomposite Material and Application in Polymer Solar Cells

“…The GDZO solution (12 mg mL −1 in trifluoroethanol) was spin‐coated on ITO at 2000 rpm 60 s. After thermal annealing at 100 °C for 15 min in air, GDZO film is formed. To investigate the morphology and surface wettability of GDZO, SEM, and contact angle of water measurements were performed, as shown in Figure (b–g) . Through the comparison of Figure (b) (ZnO film) and (e) (GDZO film), we can observe that GDZO film is more dense and smooth.…”

Additive Engineering to Grow Micron‐Sized Grains for Stable High Efficiency Perovskite Solar Cells

“…[4] The I-V hysteresis in PSCs is related to the unbalanced photoexcited electrons and holes, ferroelectric polarization, ion migration, charge carrier trapping, transient capacitive current, and so on. [7][8][9][10][11] Thus, it would be highly demanded to obtain high-efficient, hysteresis-less even hysteresis-free, and simultaneously stable PSCs by developing an effective methodology for precise perovskite film amelioration.The addition of a tiny amount of chemical additives in the perovskite precursor solution has been widely demonstrated as one of the most effective strategies to control the crystallization process, [12,13] like grain size or morphology of perovskite thin film, thus enhancing the PCE of the PSC devices. It has been demonstrated that high-quality perovskite thin films play a vital role in obtaining highperformance PSCs with excellent stability since the surface morphology and crystallization behavior of perovskite thin films can significantly affect the photoelectric characteristics, such as the charge carrier mobility, charge separation and collection efficiencies, recombination mechanics, lifetime, and diffusion-length of perovskite thin films.…”

Solvent Engineering Using a Volatile Solid for Highly Efficient and Stable Perovskite Solar Cells

“…In addition to the 3D perovskite related features, a diffraction signal at 12.5° originating from the (001) plane of the hexagonal PbI 2 is observed for the pristine film4 and a very weak signal at 11.6° originating from the yellow phase of FA‐based perovskite (δ‐FAPbI 3 ) is observed for TGA‐modified perovskite film 40. The addition of GA does not alter the crystal orientation relative to the pristine perovskite film, but the crystallinity is improved with the enhanced XRD intensity 41–43. In contrast, the addition of TGA affects the crystal orientation, resulting in an increased intensity of the (101) peak at 13.9° relative to the (211) peak at 31.4°, their ratio changes from 2.55 to 9.52 44.…”