Solvent Engineering for Ambient-Air-Processed, Phase-Stable CsPbI₃ in Perovskite Solar Cells

Abstract

Inorganic CsPbI3 perovskite solar cells (PSCs) owning comparable photovoltaic performance and enhanced thermal stability compared to organic-inorganic hybrid perovskites have attracted enormous interest in the past year. However, it is still a challenge to stabilize the desired black α-CsPbI3 perovskites in ambient air for photovoltaic applications. Herein, sequential solvent engineering including the addition of hydroiodic acid (HI) and subsequent isopropanol (IPA) treatment for fabricating stable and working CsPbI3 PSCs is developed, and a novel low-temperature phase-transition route from new intermediate Cs4PbI6 to stable α-CsPbI3 is also released for the first time. As such, the as-prepared PSCs give a relatively high power conversion efficiency (PCE) of 4.13% (reverse scan), and the steady-state power output of 1.88% is confirmed for the selected cell with an initial PCE of 3.13%. To the best of our knowledge, this is the first demonstration of fabricating CsPbI3 inorganic PSCs under fully open-air conditions.

Fully‐Inorganic Trihalide Perovskite Nanocrystals: A New Research Frontier of Optoelectronic Materials

“…[161][162][163] Therefore, the mixing of the organic cation with inorganic ones is an important strategy to achieve high performance perovskite solar cells in terms of efficiency and thermal and structural stability. [44,45,[149][150][151][152][165][166][167] For example, Snaith's group presented an inorganic perovskite CsPbI 3 -based solar cell for the first time. [44,45,149,150,165,166] Consequently, with the aim to increase stability and efficiency, several groups have explored all-inorganic perovskite photovoltaics, including planar and hole-conductor-free devices.…”

“…[151] By replacing the fragile methylammonium cation with robust cesium, the optical and thermal stability is increased without a decrease in photovoltaic performance. [151,152] To stabilize the desired α-phase CsPbI 3 , Snaith et al explored a low-temperature additive route to in situ form α-phase CsPbI 3 solution-processed film in a fully air-free environment, which mainly includes adding hydroiodic acid to the precursor solution prior to spin-coating as well as subsequent annealing at only 100 °C. [44,151] Although α-phase CsPbI 3 has excellent optical−electric properties including a desired bandgap of about 1.70 eV and a strong absorption in the whole visible light region, it can rapidly degrade to the undesired non-perovskite δ-phase in ambient air, unsuitable for photovoltaic application.…”

Efficiency and stability enhancement of perovskite solar cells by introducing CsPbI3 quantum dots as an interface engineering layer

“…Recently, all-inorganic perovskite materials have exhibited better environmental durability than organic −inorganic hybrid perovskite materials 20 . Furthermore, the band position of inorganic perovskite quantum dot (QD) materials is tunable by adjusting the components of the QDs 21 .…”

A Facile Low Temperature Fabrication of High Performance CsPbI2Br All‐Inorganic Perovskite Solar Cells

“…[27,29] While the typical anti-solvent method prepared CsPbI 2 Br films exhibited the absorbance edge at %450 nm, a signal of δ phase. [32] Figure 1c listed XRD patterns of our low temperature fabricated red brown CsPbI 2 Br thin films and the peaks at 2θ ¼ 14.6, 29.3, and 20.8 are assigned to the (100), (200), and (110) planes of cubic α phase pure CsPbI 2 Br. [28,33,34] In contrast, the traditional method prepared CsPbI 2 Br film exhibits XRD pattern of a typical δ-phase CsPbI 2 Br.…”