Thermodynamically stabilized β-CsPbI3–based perovskite solar cells with efficiencies >18%

By Yong Wang, M. I. Dar, L. Ono, Taiyang Zhang, Miao Kan, Yawen Li, Lijun Zhang, Xingtao Wang, Yingguo Yang, Xingyu Gao and 3 more. Science, 2019

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Tetragonal phases for perovskite solar cells The power conversion efficiencies (PCEs) of all-inorganic perovskites are lower than those of materials with organic cations. This is in part because these materials have larger bandgaps. The cubic crystal phases of these materials also exhibit poor stability. Wang et al. synthesized the tetragonal β-phase of CsPbI3 from HPbI3 and CsI. The material exhibited higher stability and a more favorable bandgap, which allowed for PCEs of 15%. Passivation of the surface trap state with choline iodide boosted PCEs to 18%. Science, this issue p. 591 The more stable orthorhombic phase of CsPbI3 yields more efficient solar cells. Although β-CsPbI3 has a bandgap favorable for application in tandem solar cells, depositing and stabilizing β-CsPbI3 experimentally has remained a challenge. We obtained highly crystalline β-CsPbI3 films with an extended spectral response and enhanced phase stability. Synchrotron-based x-ray scattering revealed the presence of highly oriented β-CsPbI3 grains, and sensitive elemental analyses—including inductively coupled plasma mass spectrometry and time-of-flight secondary ion mass spectrometry—confirmed their all-inorganic composition. We further mitigated the effects of cracks and pinholes in the perovskite layer by surface treating with choline iodide, which increased the charge-carrier lifetime and improved the energy-level alignment between the β-CsPbI3 absorber layer and carrier-selective contacts. The perovskite solar cells made from the treated material have highly reproducible and stable efficiencies reaching 18.4% under 45 ± 5°C ambient conditions.

Subfields: Electrical and Electronic Engineering, Materials Chemistry

View Paper: https://www.semanticscholar.org/paper/386143c96220d4da8f249d361ee72ef1fd7ef00f