Unveiling Roles of Tin Fluoride Additives in High‐Efficiency Low‐Bandgap Mixed Tin‐Lead Perovskite Solar Cells

Abstract

Low‐bandgap mixed tin–lead perovskite solar cells (PSCs) have been attracting increasing interest due to their appropriate bandgaps and promising application to build efficient all‐perovskite tandem cells, an effective way to break the Shockley–Queisser limit of single‐junction cells. Tin fluoride (SnF2) has been widely used as a basis along with various strategies to improve the optoelectronic properties of low‐bandgap SnPb perovskites and efficient cells. However, fully understanding the roles of SnF2 in both films and devices is still lacking and fundamentally desired. Here, the functions of SnF2 in both low‐bandgap (FASnI3)0.6(MAPbI3)0.4 perovskite films and efficient devices are unveiled. SnF2 regulates the growth mode of low‐bandgap SnPb perovskite films, leading to highly oriented topological growth and improved crystallinity. Meanwhile, SnF2 prevents the oxidation of Sn2+ to Sn4+ and reduces Sn vacancies, leading to reduced background hole density and defects, and improved carrier lifetime, thus largely decreasing nonradiative recombination. Additionally, the F− ion preferentially accumulates at hole transport layer/perovskite interface with high SnF2 content, leading to more defects. This work provides in‐depth insights into the roles of SnF2 additives in low‐bandgap SnPb films and devices, assisting in further investigations into multiple additives and approaches to obtain efficient low‐bandgap PSCs.

Oxalate Pushes Efficiency of CsPb0.7Sn0.3IBr2 Based All‐Inorganic Perovskite Solar Cells to over 14%

“…The Sn 3d 5/2 core spectra of the films were deconvoluted into two peaks at 486.5 and 487.2 eV, which are attributed to Sn 2+ and Sn 4+ , respectively, as presented in Figure 5d. [47,48] Clearly, the ZnOX film reveals a much weaker Sn 4+ peak than that control film, indicating that the introduction of ZnOX can effectively suppress oxidation of Sn 2+ in mixed Pb-Sn perovskite films, in line with Figure 2b related discussions. In addition, the binding energy shift of the Pb 4f shown in Figure 5e further indicates the interaction between ZnOX and the perovskite film, which is consistent with the FTIR and NMR results (Figure 2e; Figure S3, Supporting Information).…”

Influence of Temperature on Exciton Dynamic Processes in CuPc/C60 Based Solar Cells

“…No significant differences in current readings were found over the investigated temperature range. In addition, the degradation of the device's performance was negligible during the measurements; the J-V characteristics under AM1.5G, 100 mW/cm 2 at room temperature, after measurements in the probe station, displayed a short circuit current, Jsc, of 4.09 ± 0.07 mA/cm 2 , an open circuit voltage, Voc, of 0.49 ± 0.02 V, and a fill factor, FF, of 57 ± 2%, which was the same performance as before loading the device in the probe station.…”

“…The exciton and charge dynamic processes, including (i) exciton generation, (ii) exciton diffusion, (iii) exciton dissociation, (iv) free charge transportation and (v) charge collection are five important processes that determine the performance of organic solar cells (OSCs) and perovskite solar cells (PSCs) [1][2][3]. Though the power conversion efficiency (PCE) of OSCs has been found to be over 17% [4], further improvement in performance has encountered a bottleneck due to the limited understanding towards how these dynamic processes determine the performance of OSCs.…”

Synergistic Passivation of Perovskite Absorber Films for Efficient Four‐Terminal Perovskite/Silicon Tandem Solar Cells

“…These results are shown in the photocurrent distribution more clearly as depicted in Figure 3c, which indicate that the fluoride ion has strong electronegativity. [ 15,42 ] Thereby, the introduction of NaF in the perovskite precursor solution not only enhanced the grain size (Figure 2), but also passivated the GBs (Figure 3).…”