Chemically Stable Black Phase CsPbI₃ Inorganic Perovskites for High‐Efficiency Photovoltaics

Abstract

Research on chemically stable inorganic perovskites has achieved rapid progress in terms of high efficiency exceeding 19% and high thermal stabilities, making it one of the most promising candidates for thermodynamically stable and high‐efficiency perovskite solar cells. Among those inorganic perovskites, CsPbI3 with good chemical components stability possesses the suitable bandgap (≈1.7 eV) for single‐junction and tandem solar cells. Comparing to the anisotropic organic cations, the isotropic cesium cation without hydrogen bond and cation orientation renders CsPbI3 exhibit unique optoelectronic properties. However, the unideal tolerance factor of CsPbI3 induces the challenges of different crystal phase competition and room temperature phase stability. Herein, the latest important developments regarding understanding of the crystal structure and phase of CsPbI3 perovskite are presented. The development of various solution chemistry approaches for depositing high‐quality phase‐pure CsPbI3 perovskite is summarized. Furthermore, some important phase stabilization strategies for black phase CsPbI3 are discussed. The latest experimental and theoretical studies on the fundamental physical properties of photoactive phase CsPbI3 have deepened the understanding of inorganic perovskites. The future development and research directions toward achieving highly stable CsPbI3 materials will further advance inorganic perovskite for highly stable and efficient photovoltaics.

p‐Type Carbon Dots for Effective Surface Optimization for Near‐Record‐Efficiency CsPbI2Br Solar Cells

“…The PL intensity of perovskite films with B-CDs surface modification shows distinct quenching, regardless of whether the perovskite film was spin-coated with Spiro-OMeTAD, which means that the perovskite films with B-CDs modification are favorable to hole extraction. [5] In order to explore the mechanism of fluorescence quenching, ultraviolet photoelectron spectroscopy (UPS) was conducted to investigate the conductivity type of B-CDs and CsPbI 2 Br, as in Figure S4a-c in the Supporting Information, which shows the Fermi level of B-CDs lies below the quasi-Fermi level and above the valence band (VB). Therefore, the prepared B-CDs are a p-type semiconductor.…”

“…[3,4] To address these issues, inorganic CsPbX 3 (X = I − , Br − , Cl − or mixed) perovskites with Cs + as the only cation has attracted great interest in recent years. [5][6][7] With the increase of iodine content, the efficiency of inorganic PSCs increases, while with the increase of bromine content, the stability of the device increases, and thus there is an inevitable compromise between stability and efficiency in inorganic CsPbX 3 PSCs. By balancing the stability and efficiency, the mixed-halide CsPbI 2 Br perovskite is regarded as a potential material for application in tandem photovoltaics.…”

In‐Situ Hot Oxygen Cleansing and Passivation for All‐Inorganic Perovskite Solar Cells Deposited in Ambient to Breakthrough 19% Efficiency

“…The HOCP-treated device maintained 91.2% of its initial PCE value (Figure 6f), which is higher in contrast to the one without HOCP treatment (91.2% versus 83.0%), indicating better stability for the former because it has fewer halide vacancies without organic residues. [67]…”

All-inorganic perovskite solar cells with efficiency >20%

“…Nevertheless, the perovskite structure (namely black phase) of CsPbI 3 is only maintained at high temperatures (175-360°C) because of the small radius of Cs + ions. At room temperature, the black phase is easily converted to the non-perovskite yellow phase (δ-CsPbI 3 ) [2].…”