Europium and Acetate Co‐doping Strategy for Developing Stable and Efficient CsPbI₂Br Perovskite Solar Cells

Abstract

All‐inorganic perovskite solar cells have developed rapidly in the last two years due to their excellent thermal and light stability. However, low efficiency and moisture instability limit their future commercial application. The mixed‐halide inorganic CsPbI2Br perovskite with a suitable bandgap offers a good balance between phase stability and light harvesting. However, high defect density and low carrier lifetime in CsPbI2Br perovskites limit the open‐circuit voltage (Voc < 1.2 V), short‐circuit current density (Jsc < 15 mA cm−2), and fill factor (FF < 75%) of CsPbI2Br perovskite solar cells, resulting in an efficiency below 14%. For the first time, a CsPbI2Br perovskite is doped by Eu(Ac)3 to obtain a high‐quality inorganic perovskite film with a low defect density and long carrier lifetime. A high efficiency of 15.25% (average efficiency of 14.88%), a respectable Voc of 1.25 V, a reasonable Jsc of 15.44 mA cm−2, and a high FF of 79.00% are realized for CsPbI2Br solar cells. Moreover, the CsPbI2Br solar cells with Eu(Ac)3 doping demonstrate excellent air stability and maintain more than 80% of their initial power conversion efficiency (PCE) values after aging in air (relative humidity: 35–40%) for 30 days.

Controlled n‐Doping in Air‐Stable CsPbI2Br Perovskite Solar Cells with a Record Efficiency of 16.79%

“…As shown in Figure S12 in the Supporting Information, the optimized device showed a slow decrease of PCE over time, maintaining ≈90% of its initial efficiency after 1080 h. During the same aging process, the PCE of the control CsPbI 2 Br PSC dropped dramatically to ≈70% of its initial value. These results indicate that the optimized CsPbI 2 Br PSCs demonstrate better stability than the control devices; the enhanced stability of the optimized PSCs is probably due to the surface passivation effect of CaCl 2 on the perovskite film 40. Operational stability of the optimized CsPbI 2 Br PSC was measured using a Xenon lamp at AM1.5 solar illumination in air (RH: ≈25%) 41–43.…”

Precursor Engineering for Ambient‐Compatible Antisolvent‐Free Fabrication of High‐Efficiency CsPbI2Br Perovskite Solar Cells

“…Incorporating their bandgap (1.91 eV) calculated from UV–vis absorption curves, the energy level alignments of the control and optimized CsPbI 2 Br PSCs are shown in Figure 7d. The control and optimized CsPbI 2 Br films are all n‐type semiconductors (their Fermi levels are close to the conduction bands), [ 41,42 ] and the Fermi level of the optimized perovskite film is higher than that of the control film. The elevated Fermi level of the optimized perovskite is possibly due to fewer charged defects on the surface and grain boundaries that could pin the Fermi level at a low energy level.…”

Organic Ligands Armored ZnO Enhances Efficiency and Stability of CsPbI2Br Perovskite Solar Cells

“…Admittedly, there are hysteresis in all these PSCs, agreeing well with literature reports. [16,30,[32][33][34] The enhanced V OC arises from more matched energy level alignment between ZnO (−4.31 eV) and CsPbI 2 Br (−4.16 eV) compared to TiO 2 (−4.43 eV) ( Figure S1a, Supporting Information), which is conducive to decrease energy barrier and facilitate electron transport at the ETMs/perovskite interface. [29,35] Besides the quality of the perovskite layer grown on these ETMs and the interfacial charge transport efficiency, the higher electron mobility and transparency of ZnO also contribute to promote J SC and FF, which have been widely reported in many publications.…”