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In situ cyclized polyacrylonitrile (CPAN) is developed to replace n‐type metal oxide semiconductors (TiO2 or SnO2) as an electron selective layer (ESL) for highly efficient and stable n‐i‐p perovskite solar cells (PSCs). The CPAN layer is fabricated via facile in situ cyclization reaction of polyacrylonitrile (PAN) coated on a conducting glass substrate. The CPAN layer is robust and insoluble in common solvents, and possesses n‐type semiconductor properties with a high electron mobility of 4.13×10−3 cm2 V−1 s−1. With the CPAN as an ESL, the PSC affords a power conversion efficiency (PCE) of 23.12 %, which is the highest for the n‐i‐p PSCs with organic ESLs. Moreover, the device with the CPAN layer holds superior operational stability, maintaining over 90 % of their initial efficiency after 500 h continuous light soaking. These results confirm that the CPAN layer would be a desirable low‐cost and efficient ESL for n‐i‐p PSCs and other photoelectronic devices with high performance and stability. [ABSTRACT FROM AUTHOR]

• A single-crystal complex FA 4 Pb 3 I 6 Ac 4 is synthesized. • FAPbI 3 perovskite film has been fabricated from FA 4 Pb 3 I 6 Ac 4 via anion-exchange. • The FAPbI 3 film is dense and uniform with low trap-state density. • The PSC shows a PCE of 23.65% with enhanced stability. PbI 2 as precursor has been extensively employed for the fabrication of organic–inorganic hybrid perovskite films for high-efficiency perovskite solar cells (PSCs) by using two-step solution deposition method. However, the resultant perovskite film suffers from the incomplete reaction of PbI 2 and the volumetric expansion of the film, affecting both the performance and stability of the PSCs. Here, a single-crystal complex FA 4 Pb 3 I 6 Ac 4 (Ac−: CH 3 COO−) is synthesized, and utilized to replace PbI 2 for the fabrication of FAPbI 3 -based perovskite film in ambient conditions. The solution-processed crystal complex has good film-forming ability, and can be directly converted into stable black-phase FAPbI 3 perovskite at room temperature through anion exchange reaction between Ac− and I− upon coating with iodide salt solution. By the strategy, a dense and uniform perovskite film is obtained with reduced trap-state density and prolonged charge lifetime. The champion device delivers a power conversion efficiency (PCE) of 23.65% with high reproductivity. Importantly, the unencapsulated device exhibits a dramatically improved operational stability under temperature and humidity conditions. [ABSTRACT FROM AUTHOR]

• Multifunctional interlayer for highly stable and efficient P3HT-based PSCs. • Simultaneously passivating the defects of perovskite and improving the interface contaction and charge extraction. • Inducing the oriented self-assembly of P3HT and promoting efficient charge transfer. • Enhancing the thermal and moisture resistance of the perovskite film. Poly (3-hexylthiophene) (P3HT) has been recognized to be a potential hole-transport material (HTM) for stable and efficient perovskite solar cells (PSCs) due to its low cost, high hole mobility, and solution processability. However, the uncontrolled configuration of the polymer chains and the poor contact on the perovskite film restrain the charge extraction and transport in the devices. Here, we demonstrate a simple and versatile strategy for the fabrication of stable and efficient P3HT-based PSCs, using 1-hexyl-2,5-dimethyl-1H-pyrrole-3-carboxylic acid (HPCA) as interlayer between perovskite and P3HT layers. The carboxyl group in HPCA can effectively suppress anion-vacancy defects at the grain boundaries and surface of the perovskite film, reducing the trap state density and improving the carrier lifetimes. Moreover, the peripheral hexyl-pyrrole in HPCA can improve the interface contact between the perovskite and P3HT, and regulate P3HT orientation and improve charge extraction and transport in the device. As a result, the PSC using the dopant-free P3HT HTM yields a power conversion efficiency (PCE) of 20.8%, along with superior stability at a relative humidity of 60%, heat at 80 °C, or under continuous light illumination. [ABSTRACT FROM AUTHOR]

• In-Situ Polymerization of conducting polymer PEDOT in Perovskite Thin Films. • Simultaneously passivating the defects and improving carrier extraction efficiency. • Enhancing the thermal and moisture resistance of the perovskite film. • The PSCs with 22.58% PCE with enhanced stability. Solution-processed polycrystalline perovskite films have detrimental defects in the bulk and surfaces/grain boundaries, especially the uncoordinated lead ions (Pb2+) with low formation energy, limiting both the performance and stability of the photovoltaic devices. In this work, a conductive polymer poly(3,4-ethylenedioxythiophene) (PEDOT) is incorporated into a bulk perovskite film by a facile in-situ polymerization method, where 5-bromo-2,3-dihydro-thieno[3,4-b][1,4]dioxine (BEDOT) as monomer is directly added to a perovskite precursor solution and then in-situ polymerized within the perovskite film during the film formation. The PEDOT is chemically anchored at the surface and grain boundaries of the perovskite film via interaction of sulfur and oxygen atoms in PEDOT with uncoordinated lead ions in the perovskite, passivating the surface and bulk defects and also improving the charge extraction efficiency in the solar cell. Moreover, robust and hydrophobic properties of PEDOT can enhance the thermal and moisture resistance of the perovskite film. As a result, a champion power conversion efficiency (PCE) of 22.58% is achieved, along with significantly enhanced environmental, thermal, and light-soaking stability. [ABSTRACT FROM AUTHOR]

Inorganic cesium lead iodide perovskite CsPbI3 is attracting great attention as a light absorber for single or multi‐junction photovoltaics due to its outstanding thermal stability and proper band gap. However, the device performance of CsPbI3‐based perovskite solar cells (PSCs) is limited by the unsatisfactory crystal quality and thus severe non‐radiative recombination. Here, vacuum‐assisted thermal annealing (VATA) is demonstrated as an effective approach for controlling the morphology and crystallinity of the CsPbI3 perovskite films formed from the precursors of PbI2, CsI, and dimethylammonium iodide (DMAI). By this method, a large‐area and high‐quality CsPbI3 film is obtained, exhibiting a much reduced trap‐state density with prolonged charge lifetime. Consequently, the solar cell efficiency is raised from 17.26 to 20.06 %, along with enhanced stability. The VATA would be an effective approach for fabricating high‐performance thin‐film CsPbI3 perovskite optoelectronics. [ABSTRACT FROM AUTHOR]

Inorganic cesium lead iodide perovskite CsPbI3 is attracting great attention as a light absorber for single or multi‐junction photovoltaics due to its outstanding thermal stability and proper band gap. However, the device performance of CsPbI3‐based perovskite solar cells (PSCs) is limited by the unsatisfactory crystal quality and thus severe non‐radiative recombination. Here, vacuum‐assisted thermal annealing (VATA) is demonstrated as an effective approach for controlling the morphology and crystallinity of the CsPbI3 perovskite films formed from the precursors of PbI2, CsI, and dimethylammonium iodide (DMAI). By this method, a large‐area and high‐quality CsPbI3 film is obtained, exhibiting a much reduced trap‐state density with prolonged charge lifetime. Consequently, the solar cell efficiency is raised from 17.26 to 20.06 %, along with enhanced stability. The VATA would be an effective approach for fabricating high‐performance thin‐film CsPbI3 perovskite optoelectronics. [ABSTRACT FROM AUTHOR]

3D tin-based halide perovskites are promising light absorbers for perovskite solar cells (PSCs) due to their non-toxicity, suitable optical band gaps, and excellent optoelectronic properties. However, the inherent rapid crystallization and easy oxidation of Sn2+ to Sn4+ in 3D perovskites result in a low power conversion efficiency (PCE) and poor stability of tin perovskite solar cells compared with the lead counterparts. In this report, quasi-2D hybrid tin-based perovskite films are fabricated by using 2-thiopheneethylammonium (TEA+) as the spacer cation in MASnI3 (MA: CH3NH3+), leading to the formation of quasi-2D perovskite films with high orientation and a low content of Sn4+. As a result, the perovskite solar cells show a considerable power-conversion efficiency of 6.8%, which is among the highest values reported for MASnI3-based solar cells. Moreover, the devices exhibited excellent stability compared with the device without TEAI. [ABSTRACT FROM AUTHOR]