Room-Temperature Mixed-Solvent-Vapor Annealing For High Performance Perovskite Solar Cells

Perovskite solar cells(PSCs) have attracted great attention because of their high energy conversion efficiency and low material costs. Champion energy conversion efficiency has exceeded 21%. The stability and reproducibility of perovskite devices are still the research focus. One of the main issues encountered in PSCs fabrication is to explore a reliable method for preparing perovskite layer with a fine-control morphology. To date, one-step; two-step; dual-source evaporation; vapor-assisted solution process have been successfully used to fabricate high quality perovskite films. In addition, a poor solvent of perovskite can be introduced to accelerate the nucleation of perovskite crystals when concentrate perovskite precursor solution. In this paper, we introduce a room-temperature mixed-solvent-vapor annealing(rtMSVA) method to fabricate high performance perovskite solar cells based on MAPbI3-xClx without the need for thermal annealing(TA).1. In the first part, we presented the summary of the background and current research progress of perovskite solar cells.2. In the second part, study of the effect of TA and rtMSVA methods on preparing perovskite thin-films in normal PSCs was introduced. The device structure is ITO/PEDOT:PSS/CH3NH3PbI3-xClx/PCBM/LiF/Al. In the work, TA and rtMSVA were used to induce the crystallization of perovskite, which resulted in the transformation of perovskite crystal structure from orthorhombic phase to cubic /tetragonal phase. Compared with conventional TA method, perovskite films prepared with rtMSVA had a better crystallinity and smoother surface morphology, which led to a big improvement of power conversion efficiency(PCE) of PSCs. PCE increased from 12.76% to 16.41%. And based on this method, we fabricated large area PSCs on ITO and PET/Ag-grid substrates with an active area of 1.21 cm2. And the PCE reached 11.01% and 7.5%, respectively. Best of our knowledge, this is the highest efficiency of PSCs with such a large active area, when we reported this work. This research project aims to develop a novel method for the preparation of perovskite thin films and use this method for the fabrication of PSCs.3. In the third part, conclusion and outlook of rtMSVA method: a broad absorption HC(NH2)2PbI3 perovskite material was introduced as the light absorbing layer in normal device structure. It was difficult to obtain a fine-control morphology of perovskite films. Here rtMSVA method was introduced for adjusting the morphology of perovskite films, aiming at to a high quality and large grain size perovskite film. The PCE increased from 2.59% to 9.37% with the single TA method.