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CsPbI3 perovskite is a promising light absorber in perovskite solar cells (PSCs) due to its suitable bandgap (Eg) and high chemical stability, but the perovskite phase is metastable in ambient atmosphere and prone to defect formation. To enhance phase stability and reduce defects, forming a low dimensional (LD) perovskite on CsPbI3 has proved effective. However, the energy levels for most of low‐conductivity LD perovskites are not very compatible with those of CsPbI3, which will impair charge separation and device performance. Herein, a new 1D perovskite (5‐Azaspiro[4.4]nonan‐5‐ium lead triiodide, ASNPbI3) with compatible energy levels and a large Eg is reported as a capping layer. The p‐type ASNPbI3 forms a p‐n heterojunction with n‐CsPbI3 with a staggered band alignment, considerably enhancing the carrier separation. Besides, by pre‐forming a ASNPbI3 at an intermediate stage, defects are suppressed in perovskite film. Consequently, the CsPbI3 PSCs based on carbon electrode without hole transporter (C‐PSCs) achieves a PCE of 18.34%, which is among the highest‐reported values for inorganic C‐PSCs. Furthermore, the hydrophobic ASNPbI3 capping layer has a high thermal stability that greatly enhances perovskite phase stability. Hence, the CsPbI3 C‐PSCs maintains 68% of its initial PCE after 400 h aging at 85°C in a N2 glovebox. [ABSTRACT FROM AUTHOR]

Sb2(S, Se)3 solar cells have shown great promise due to the advantages of low cost, non-toxic and high stability. However, traditional devices commonly use noble metal as the back electrode, which not only increases device cost but also limits device stability. Herein, carbon materials are used to replace the noble metals in Sb2(S, Se)3 solar cells. In addition, to grow high-quality Sb2(S, Se)3 films, a two-step hydrothermal method was developed. The carbon-based Sb2(S, Se)3 solar cells based on the above film achieved a power conversion efficiency (PCE) of 2.76%. After inserting a stable P3HT layer at the Sb2(S, Se)3 film/carbon interface, hole extraction was enhanced and the PCE was promoted to 4.15%. This work brings out a promising route to produce emerging solar cells with cost-effective and stable materials. [ABSTRACT FROM AUTHOR]

The suitable optical bandgap and high chemical stability have made inorganic CsPbI 3 perovskite become a promising light absorber in perovskite solar cells (PSCs). However, it is still a great challenge to obtain a high-quality CsPbI 3 perovskite film because of its phase instability, let alone composition manipulation. Herein, we report a new and general strategy, extracting ammonium halide by solvent (EAH-S), to solve the above problems. During the EAH-S process, ammonium halide is introduced into the traditional precursor solution to form a transitive compound (e.g. 3D, 2D and 1D hybrid perovskites). Then, the transitive compound is soaked in a solvent with moderate polarity (e.g. ethanol, methanol, isopropanol), during which ammonium halide would be extracted to promote the crystallization of CsPbI 3 perovskite. The extraction of ammonium halide is proved to be the vital process, which could release PbI 2 and prompt the nucleation of p -CsPbI 3 at the interface with the assistance of ammonium ions. By combining the EAH-S method with a conventional annealing process, the composition of CsPbI 3 perovskite film could be finely manipulated, and the film quality is well improved. More promisingly, the carbon-based CsPbI 3 PSCs without hole transporter achieve a efficiency of 15.35%, a new record for inorganic C-PSCs. [Display omitted] • Demonstrate a new and general strategy, extracting ammonium halide by solvent (EAH-S), to obtain CsPbI 3 perovskite film. • EAH-S could release PbI 2 and prompt the nucleation of p-CsPbI 3 at the interface with the assistance of ammonium ions. • The carbon-based CsPbI 3 PSCs without hole transporter achieve a efficiency of 15.35%, a new record for inorganic C-PSCs. [ABSTRACT FROM AUTHOR]

The application of CsPbI 3 inorganic perovskite in carbon-based perovskite solar cells without hole transporter (C-PSCs) is expected to enhance device stability. However, due to the lower hole selectivity of carbon electrode than that of hole transporter, the efficiency of CsPbI 3 C-PSCs is significantly suppressed. Herein, size mismatch-induced cation segregation in CsPbI 3 is studied and employed to solve the problem. After treating CsPbI 3 with CsX (X Br, Cl and F) ethanol solutions, the larger size mismatch between X- and I- ions would induce the more obvious cation segregation. The moderate size mismatch between I- and Cl- ions allows a partial substitution of I- ions with Cl- ions in CsPbI 3 to form energy level gradient, and the CsCl residue on the surface tends to react with CsPbI 3 to generate 2D Cs 2 PbI 2 Cl 2 nanosheets, serving as an electron blocking layer. The synergistic effect of the energy level gradient and the electron blocking layer well improves hole selectivity at CsPbI 3 /carbon interface to reduce carrier recombination loss. As a result, the C-PSCs based on the CsCl-treated CsPbI 3 achieve an efficiency of 15.23%, a record value for inorganic C-PSCs. [Display omitted] • The larger size mismatch between Br, Cl, F and I ions is found to induce cation segregation after CsX post treatment. • The moderate size mismatch leads to substitution of I with Cl in CsPbI 3 and form composition and energy level gradient. • The CsCl residue on the surface tends to react with CsPbI 3 to form 2D Cs 2 PbI 2 Cl 2 nanosheets as an electron blocking layer. • The energy level gradient and electron blocking layer improves the hole selectivity to reduce recombination loss. • The C-PSCs based on the CsCl-treated CsPbI 3 achieve an efficiency of 15.2%, a new record for inorganic C-PSCs. [ABSTRACT FROM AUTHOR]

The inorganic CsPbI 3 perovskite obtained from dimethylammonium iodide (DMAI)-related strategies have greatly promoted the development of CsPbI 3 perovskite solar cells (PSCs). However, deeper understandings are urgently needed to further enhance device performance. Herein, the crystallization processes of DMAI-based strategy are systematically studied and some new understandings are proposed. During annealing, β -phase-like CsPbI 3 is first formed and then gradually transits to γ -phase-like structure. DMA ions tend more to form DMAPbI 3 in the system, implying the amount of alloyed DMA ions in CsPbI 3 would be very limited. In addition, the pre-generated Cs 4 PbI 6 plays an important role in stabilizing CsPbI 3 perovskite phase at low temperature. These findings help us to finely manipulate film composition, and the quality of CsPbI 3 film is substantially improved after simultaneously suppressing the formation of δ -CsPbI 3 , minimizing DMAPbI 3 residual and generating PbI 2 passivator. More promisingly, the carbon-based CsPbI 3 PSCs without hole transporter achieve a record efficiency of 14.6%. [Display omitted] • The crystallization processes of DMAI-based strategy are systematically studied and some important understandings are established. • Film composition are finely manipulated, and the quality of CsPbI 3 film is substantially improved. • The carbon-based CsPbI 3 PSCs without hole transporter achieve an efficiency of 14.6%, a new record for carbon-based inorganic PSCs. [ABSTRACT FROM AUTHOR]

The power conversion efficiencies of organic-inorganic hybrid perovskite solar cells (PSCs) have been boosted from 3.8% to over 25% in about ten years. However, low device stability still impedes their practical applications. In the last few years, the inorganic PSCs based on carbon electrodes (C–PSCs) have gradually become one of the promising resolutions, and up to now, much progress has been made. Herein, recent developments in C–PSCs, including (1) device structure and working principles, (2) categorical progress of CsPbBr 3 , CsPbI 3-x Br x , CsPbI 3 and other inorganic C–PSCs, are reviewed. Promising research directions (e.g. developing suitable deposition methods, improving phase stability, tuning energy band structure, modifying perovskite/carbon interface and exploiting new inorganic perovskites) are then suggested to promote the development of inorganic C–PSCs. Image 1 • Device structure and working principles of inorganic C–PSCs are systematically reviewed and discussed. • Categorical progress of CsPbBr 3 , CsPbI 3-x Br x , CsPbI 3 and other inorganic C–PSCs are systematically reviewed and discussed. • Current issues and future research directions for inorganic C–PSCs are pointed out and highlighted. [ABSTRACT FROM AUTHOR]

Defects formed at the surface, buried interface and grain boundaries (GB) of CsPbI 3 perovskite films considerably limit photovoltaic performance. Such defects could be passivated effectively by the most prevalent post modification strategy without compromising the photoelectric properties of perovskite films, but it is still a great challenge to make this strategy comprehensive to different defects spatially distributed throughout the films. Herein, a spatially selective defect management (SSDM) strategy is developed to roundly passivate various defects at different locations within the perovskite film by a facile one-step treatment procedure using a piperazine-1,4-diium tetrafluoroborate (PZD(BF 4) 2) solution. The small-size PZD2+ cations could penetrate into the film interior and even make it all the way to the buried interface of CsPbI 3 perovskite films, while the BF 4 − anions, with largely different properties from I− anions, mainly anchor on the film surface. Consequently, virtually all the defects at the surface, buried interface and grain boundaries of CsPbI 3 perovskite films are effectively healed, leading to significantly improved film quality, enhanced phase stability, optimized energy level alignment and promoted carrier transport. With these films, the fabricated CsPbI 3 PSCs based on carbon electrode (C-PSCs) achieve an efficiency of 18.27%, which is among the highest-reported values for inorganic C-PSCs, and stability of 500 h at 85 °C with 65% efficiency maintenance. [ABSTRACT FROM AUTHOR]

• The drop-casting method was for the first time developed to deposit CsPbI 3 films. • A vacuum process was exploited to greatly suppress coffee ring effect (CRE). • The carbon-based CsPbI 3 PSCs achieves a new record efficiency of 16.33 %. • A large-area perovskite film with excellent uniformity is prepared by VA. Inorganic CsPbI 3 perovskite has shown much promise as a light absorber in perovskite solar cells (PSCs) due to its appropriate optical bandgap and high chemical stability. However, it is still a great challenge to deposit large-area CsPbI 3 perovskite films by existing methods (e.g. spin coating). Herein, a facile and scalable strategy based on a drop-casting process is developed. To mitigate the coffee ring effect (CRE) that commonly occurs during drop casting, a vacuum-assisted (VA) process is exploited to boost solvent extraction, which significantly reduces the difference in solvent evaporation rates at the edge and middle regions of droplets. As a result, uniform CsPbI 3 perovskite films with higher crystallinity and lower defect density are deposited by drop casting. By using the CsPbI 3 perovskite film as a light absorber, the carbon-based CsPbI 3 PSCs without hole transport layer achieves an efficiency of 16.33 %, a new record for inorganic C-PSCs. After finely controlling deposition processes, a large-area CsPbI 3 perovskite film (5 × 5 cm2) with excellent uniformity can be easily prepared by the drop casting method. [ABSTRACT FROM AUTHOR]