CsI Pre‐Intercalation in the Inorganic Framework for Efficient and Stable FA_1−x Cs_xPbI₃(Cl) Perovskite Solar Cells

Abstract

Engineering the chemical composition of organic and inorganic hybrid perovskite materials is one of the most feasible methods to boost the efficiency of perovskite solar cells with improved device stability. Among the diverse hybrid perovskite family of ABX , formamidinium (FA)-based mixed perovskite (e.g., FA Cs PbI ) possesses optimum bandgaps, superior optoelectronic property, as well as thermal- and photostability, which is proven to be the most promising candidate for advanced solar cell. Here, FA Cs PbI (Cl) is implemented as the light-harvesting layer in planar devices, whereas a low temperature, two-step solution deposition method is employed for the first time in this materials system. This paper comprehensively exploits the role of Cs in the FA Cs PbI (Cl) perovskite that affects the precursor chemistry, film nucleation and grain growth, and defect property via pre-intercalation of CsI in the inorganic framework. In addition, the resultant FA Cs PbI (Cl) films are demonstrated to exhibit an improved optoelectronic property with an elevated device power conversion efficiency (PCE) of 18.6%, as well as a stable phase with substantial enhancement in humidity and thermal stability, as compared to that of FAPbI (Cl). The present method is able to be further extended to a more complicated (FA,MA,Cs)PbX material system by delivering a PCE of 19.8%.

Formamidinium‐Based Lead Halide Perovskites: Structure, Properties, and Fabrication Methodologies

“…Furthermore, the interdiffusion method can also be used to prepare mixed‐composition perovskites . This method has been used to prepare Cs 0.1 FA 0.9 PbI 2.865 Br 0.135 films by annealing two spin‐coated layers (CsI + PbI 2 and FAI + FABr), and an efficiency of 19.3% has been obtained for a small‐area device .…”

“…However, although some film compositions of Cs x FA 1− x PbI 3− y Br y exhibited good phase stability under high humidity (77%), none of the considered compositions were found to be inert to humidity . This is in agreement with a report that storage in ambient FAPbI 3 (Cl)‐based devices led to a change in color and complete degradation within 30 h, while FA 0.9 Cs 0.1 PbI 3 (Cl)‐based devices retained a dark color and exhibited a decline in efficiency of 45% . This finding indicates that composition engineering is a promising strategy to improve the phase stability, but the devices, nevertheless, will require encapsulation to achieve a stable operation.…”

Polymer Doping for High‐Efficiency Perovskite Solar Cells with Improved Moisture Stability

“…[53] The bonding between MA + and the polymer slows down the perovskite crystallization process and therefore improves the perovskite grain quality. Figure 6d trap-state density (n t ) was therefore determined by the trapfilled limit voltage (V TFL ) as follows [55] n V eL Figure 6d trap-state density (n t ) was therefore determined by the trapfilled limit voltage (V TFL ) as follows [55] n V eL…”

Adjusting the Introduction of Cations for Highly Efficient and Stable Perovskite Solar Cells Based on (FAPbI3)0.9(FAPbBr3)0.1

“…As light blueshift also can be found, which was mentioned in the UV/Vis absorption spectra discussion (Figure 3a). [25,32] Moreover,F igure 5e presents the PCE histograms of different devices with aG aussian distribution.A na pparent variation of PCE can be observed among the four kinds of PSCs. In Figure 5d,t he results show that the device with Cs 10 -FAh as a0 .95 %P CE hysteresis, which is lower than most reportedF A-based PSCs.…”

“…[24,27] Seok and co-workers [30] introduced the MAPbBr 3 (MA = methylammonium) component into FAPbI 3 for (FAPbI 3 ) 0.85 (MAPbBr 3 ) 0. Zhou et al [32] acquired highly efficient and stable FA 1Àx Cs x PbI 3 (Cl) PSCs by the intercalation of CsI. Zhou et al [32] acquired highly efficient and stable FA 1Àx Cs x PbI 3 (Cl) PSCs by the intercalation of CsI.…”