Methylamine-assisted growth of uniaxial-oriented perovskite thin films with millimeter-sized grains

Abstract

Defects from grain interiors and boundaries of perovskite films cause significant nonradiative recombination energy loss, and thus perovskite films with controlled crystallinity and large grains is critical for improvement of both photovoltaic performance and stability for perovskite-based solar cells. Here, a methylamine (MA0) gas-assisted crystallization method is developed for fabrication of methylammonium lead iodide (MAPbI3) perovskite films. In the process, the perovskite film is formed via controlled release of MA0 gas molecules from a liquid intermediate phase MAPbI3·xMA0. The resulting perovskite film comprises millimeter-sized grains with (110)-uniaxial crystallographic orientation, exhibiting much low trap density, long carrier lifetime, and excellent environmental stability. The corresponding perovskite solar cell exhibits a power conversion efficiency (PCE) of ~ 21.36%, which is among the highest reported for MAPbI3-based devices. This method provides important progress towards the fabrication of high-quality perovskite thin films for low-cost, highly efficient and stable perovskite solar cells.

The Main Progress of Perovskite Solar Cells in 2020–2021

“…Another representative work for the improvement in perovskite layers is the fabrication of uniaxial-oriented perovskite layer with millimeter-sized grains via a methylamine gas-assisted crystallization method [ 30 ]. In this study, the methylammonium lead iodide (MAPbI 3 ) perovskite film was formed by controlling the evaporation rate of MA gas molecules from liquid intermediate phase of MAPbI 3 ·xMA in a closed system.…”

Methylamine gas healing of perovskite films: a short review and perspective

“…Besides, the release speed of MA 0 is directly related to crystallization. Song et al 30 studied the influence of the MA 0 release speed on the crystallization process from MAPbI 3 ÁxMA 0 to MAPbI 3 . In the traditional MA 0 gas healing process, the pressure of MA 0 quickly decreases (close to 0) by removing the MA 0 environment as soon as possible.…”

“…[27][28][29] Recently, it was further discovered that extending the degassing time at an elevated temperature could increase the grain size, reaching millimeters (PCE = 21.36%). 30 Large-grain perovskite films possess a low trap-state density, long charge carrier lifetime, and excellent environmental stability. Through MA 0 healing treatment, the device stability also has great enhancement due to the improvement in film quality.…”

“…For example, Qi et al reported that unencapsulated PSCs retained 90% of their initial efficiency after 800 h continuous light illumination under an N 2 atmosphere, while the control device decayed to 90% of its initial efficiency in just 300 h. 31 Song et al reported that MAPbI 3 devices fabricated using the optimized MA 0 healing method with ultra-large grains retained 85% of their initial PCEs under illumination after 1000 h in an N 2 atmosphere, whereas the control devices decayed to about 60% of their original PCEs. 30 Due to the high uniformity of the perovskite films and the device consistency, this MA 0 healing method represents a major advance in the scale-up fabrication of high-quality perovskite films and devices. 3,22,23,[31][32][33][34] However, the limitation of the MA 0 healing method is that it cannot be used for the FAPbI 3 Recently, some research groups have started studying the related mechanisms of the whole process.…”

Construction of Polyoxometalate‐Based Material for Eliminating Multiple Pb‐Based Defects and Enhancing Thermal Stability of Perovskite Solar Cells

“…[ 1 ] The quality of perovskite layer is undoubtedly the most important factor of the high‐performance planar PSC devices. [ 2,3 ] However, the soft nature of the crystal lattice makes the perovskite susceptible to environment factors and generates defects in the preparation and operation process. [ 4,5 ] On one hand, the organic species volatilize and escape from the perovskite films during the thermal annealing process, leaving numerous uncoordinated Pb 2+ traps.…”