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Tin dioxide (SnO 2) is widely utilized for the cost-effective electron transport layer (ETL) in perovskite solar cells (PSCs) owing to its excellent optoelectronic properties. However, the surface defect states present in SnO 2 ETL prepared by conventional solution methods seriously hinder the further improvement of device photovoltaic performance. It is urgently essential to develop a facile strategy to effectively minimize the adverse effects of SnO 2 ETL on PSCs. Herein, a phosphorus hetero-phenanthrene flame retardant, DOPO, is introduced as a multifunctional surface modifier to improve the interfacial properties between SnO 2 ETL and perovskite. Through systematic characterization analysis, the P O group in DOPO not only passivates the defective states on the surface of SnO 2 ETL, but also provides chemical chelation sites for the uncoordinated Pb2+ ions in the upper perovskite structure to improve the film crystalline quality. Eventually, the photoelectric conversion efficiency (PCE) of the optimized device is improved from an initial 19.74 %–22.57 %, along with significantly improved device stability. This work provides an important reference for the development of new multifunctional interface modification materials required for SnO 2 -based planar PSCs with excellent properties. [ABSTRACT FROM AUTHOR]

Tin dioxide (SnO 2) is widely used as an electron transport layer (ETL) in efficient and stable perovskite solar cells (PSCs) due to its excellent optoelectronic properties and low-temperature solution preparation process. However, SnO 2 ETLs fabricated by the conventional solution method have many defects, among which Sn dangling bonds (i.e., oxygen vacancies) are particularly prominent. Herein, a simple buried interface engineering is employed to introduce phenyl-phosphinic acid (PPA) into the surface of SnO 2 film for the preparation of highly efficient PSCs. A series of test results have shown that the phosphate group (P O) in PPA can not only passivate oxygen vacancy defects on the surface of SnO 2 , but also improve the film-forming quality of the upper perovskite, thereby exhibiting better photoelectric conversion efficiency (PCE) and stability. Ultimately, the optimized device achieves a maximum PCE of 22.81 %, an improvement of about 15 % over the control device (19.82 %). Meanwhile, the nonencapsulated device based on SnO 2 -PPA ETL shows much better storage and light stability than the control SnO 2. [Display omitted] [ABSTRACT FROM AUTHOR]

Tin dioxide (SnO 2) is widely used as an electron transport layer (ETL) in efficient and stable perovskite solar cells (PSCs) due to its excellent optoelectronic properties and low-temperature solution preparation process. However, SnO 2 ETLs fabricated by the conventional solution method have many defects, among which Sn dangling bonds (i.e., oxygen vacancies) are particularly prominent. Herein, a simple buried interface engineering is employed to introduce phenyl-phosphinic acid (PPA) into the surface of SnO 2 film for the preparation of highly efficient PSCs. A series of test results have shown that the phosphate group (P O) in PPA can not only passivate oxygen vacancy defects on the surface of SnO 2 , but also improve the film-forming quality of the upper perovskite, thereby exhibiting better photoelectric conversion efficiency (PCE) and stability. Ultimately, the optimized device achieves a maximum PCE of 22.81 %, an improvement of about 15 % over the control device (19.82 %). Meanwhile, the nonencapsulated device based on SnO 2 -PPA ETL shows much better storage and light stability than the control SnO 2. [Display omitted] [ABSTRACT FROM AUTHOR]

• A low-temperature deposition strategy for high-performance CsPbI 2 Br-based devices without DMSO in an open-air environment;. • The efficiency of optimized CsPbI 2 Br-based PSC is significantly increased to 16.44 %;. • The optimized CsPbI 2 Br-based PSCs exhibit excellent air, thermal, and light stability. High-performance CsPbI 2 Br perovskite solar cells (PSCs) often use DMF/DMSO mixed solvents to obtain sufficient film thickness due to the solubility limitations of bromide in DMF. However, the need for high-temperature annealing to form the photoactive α-CsPbI 2 Br and the difficulty of completely removing DMSO greatly limit its application prospects for commercial. Herein, we report a low-temperature deposition strategy for obtaining high-performance CsPbI 2 Br-based devices without DMSO in an open-air environment. By adding CsPbI 2 Br/DMF solution dropwise to a substrate preheated at 80 ℃, the rapid volatilization of DMF will help drive heterogeneous nucleation with lower energy barriers, thereby increasing the thickness of CsPbI 2 Br film. Meanwhile, the α-CsPbI 2 Br microcrystals formed during the spin-coating process also facilitated the formation of high-quality perovskite films. Consequently, the efficiency of optimized CsPbI 2 Br-based PSC is significantly increased to 16.44 %. To our knowledge, this efficiency value is the highest among all CsPbI 2 Br PSCs based on pure DMF solution. A facile hot-casting process is used to fabricate high-performance CsPbI 2 Br PSCs with pure DMF solutions at low temperatures (100 ℃) in open-air conditions. The optimized PSC obtained a champion PCE of 16.44 %, along with superior air and thermal stability. To our knowledge, this efficiency value is the highest among all CsPbI 2 Br PSCs based on pure DMF solution. [Display omitted] [ABSTRACT FROM AUTHOR]