Recently, lead halide-based perovskites have become one of the hottest topics in photovoltaic research because of their excellent optoelectronic properties. Among them, organic-inorganic hybrid perovskite solar cells (PSCs) have made very rapid progress with their power conversion efficiency (PCE) now at 23.7 %. However, the intrinsically unstable nature of these materials, particularly to moisture and heat, may be a problem for their long-term stability. Replacing the fragile organic group with more robust inorganic Cs+ cations forms the cesium lead halide system (CsPbX3 , X is halide) as all-inorganic perovskites which are much more thermally stable and often more stable to other factors. From the first report in 2015 to now, the PCE of CsPbX3 -based PSCs has abruptly increased from 2.9 % to 17.1 % with much enhanced stability. In this Review, we summarize the field up to now, propose solutions in terms of development bottlenecks, and attempt to boost further research in CsPbX3 PSCs.

All‐Inorganic CsPbX3 Perovskite Solar Cells: Progress and Prospects

All-inorganic perovskites are considered to be one of the most appealing research hotspots in the field of perovskite photovoltaics in the past 3 years due to their superior thermal stability compared to their organic-inorganic hybrid counterparts. The power-conversion efficiency has reached 17.06% and the number of important publications is ever increasing. Here, the progress of inorganic perovskites is systematically highlighted, covering materials design, preparation of high-quality perovskite films, and avoidance of phase instabilities. Inorganic perovskites, nanocrystals, quantum dots, and lead-free compounds are discussed and the corresponding device performances are reviewed, which have been realized on both rigid and flexible substrates. Methods for stabilization of the cubic phase of low-bandgap inorganic perovskites are emphasized, which is a prerequisite for highly efficient and stable solar cells. In addition, energy loss mechanisms both in the bulk of the perovskite and at the interfaces of perovskite and charge selective layers are unraveled. Reported approaches to reduce these charge-carrier recombination losses are summarized and complemented by methods proposed from our side. Finally, the potential of inorganic perovskites as stable absorbers is assessed, which opens up new perspectives toward the commercialization of inorganic perovskite solar cells.

Review on Recent Progress of All-Inorganic Metal Halide Perovskites and Solar Cells.

One-step anti-solvent deposition methods are widely applied in inverted perovskite solar cells (PSCs). However, anti-solvent processed films typically exhibit a small grain size and abundant defects. Herein, we propose a facile passivation approach using an ultrathin poly(triarylamine) (PTAA) layer to passivate the interfacial and grain boundary defects. An energy band alignment is realized by introducing an ultrathin PTAA layer sandwiched between the perovskite layer and the poly(3,4-ethylene dioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) layer to suppress interfacial recombination and accelerate hole transfer. By optimum design of the PTAA layer, we fabricate PSCs with a power conversion efficiency (PCE) of 19.04%, a fill factor (FF) of 82.59% and a short-circuit current density (Jsc) of 21.38 mA cm−2. To the best of our knowledge, the obtained FF value is the maximum among those reported for inverted chlorine-doped methyl perovskite solar cells (PSCs). After storage under ambient conditions for 10 days, the PCE of the PSCs with PTAA modification is still maintained at the 80% level, indicating substantially improved stability. Our work provides an effective method to boost PSCs with enhanced efficiency and stability.

Defect passivation using ultrathin PTAA layers for efficient and stable perovskite solar cells with a high fill factor and eliminated hysteresis

NH 4 Cl-Modified ZnO for High-Performance CsPbIBr 2 Perovskite Solar Cells via Low-Temperature Process

Inverted perovskite solar cells (IPSCs) have attracted great attention in recent years due to their reliable operational stability, negligible hysteresis and low-temperature fabrication process. To accelerate their commercialization, the focus of research on IPSCs has been to enhance the power conversion efficiency over the past few years. Herein, an overview of efficiency progress in IPSCs is given including the structure design, the fabrication of perovskite films and the modification of charge transport materials. Specifically, the effects of interface passivation on the performance of those devices have been emphasized. Finally, perspectives on the further development and commercialization of IPSCs are proposed, such as developing new electron transport materials and rear electrode materials, and employing field effect passivation materials and inorganic hole transport materials.

Efficiency progress of inverted perovskite solar cells

Highly efficient semitransparent CsPbIBr2 perovskite solar cells via low-temperature processed In2S3 as electron-transport-layer

Performance improvement of perovskite solar cells through enhanced hole extraction: The role of iodide concentration gradient

Simultaneous passivation of bulk and interface defects through synergistic effect of anion and cation toward efficient and stable planar perovskite solar cells

Xiaofei Hu

Papers

Defect passivation using ultrathin PTAA layers for efficient and stable perovskite solar cells with a high fill factor and eliminated hysteresis

NH 4 Cl-Modified ZnO for High-Performance CsPbIBr 2 Perovskite Solar Cells via Low-Temperature Process

Highly efficient semitransparent CsPbIBr2 perovskite solar cells via low-temperature processed In2S3 as electron-transport-layer

Performance improvement of perovskite solar cells through enhanced hole extraction: The role of iodide concentration gradient

Simultaneous passivation of bulk and interface defects through synergistic effect of anion and cation toward efficient and stable planar perovskite solar cells