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This work designed and synthesized a novel D'-A-DA'D-A-D' typed fused-ring-conjugated small-molecule cathode interlayer material (named FY1) to fabricate high-efficiency inverted PSCs and mini-PSC modules. FY1 improves electron transport, reduces energy barriers, and is ethanol-soluble for easy processing. It increases PSCs' performance, achieving 23.72% PCE and 82.3% FF, and maintains 98.5% efficiency after 850 h. [Display omitted] • A conjugated small molecule was developed and used as a CIL in PSCs. • FY1 improves interfacial contact and electron extraction. • FY1 modification realizes the work function of Ag and reduces the energy barrier. • FY1 can enhance the device performance and stability of the PSC modules. Perovskite solar cells (PSCs) represent a highly promising photovoltaic technology wherein a low-work function metal cathode is essential for efficient electron collection. The effectiveness of PSCs is significantly enhanced by a well-designed cathode interface layer (CIL). Characterized by their simple structure and impressive modification capabilities, small-molecule CILs hold considerable commercial potential for advancing the performance of PSCs. Herein, we synthesized a conjugated small-molecule CIL, named FY1, for modulating the cathode interface of inverted PSCs to enhance the power conversion efficiency (PCE) and long-term stability. FY1 not only optimized the molecule/metal contact to reduce traps but also uniformly improved the efficiency and speed of extracting photogenerated electrons, facilitating their effective extraction at the cathode interface. FY1 modification reduced the work function of Ag, subsequently lowering the energy barrier for electron transfer from the electron transport layer to the external cathode metal. By employing FY1 as a CIL, a record-high PCE of 23.72 % and a fill factor of 82.3 % were achieved in inverted PSCs. Furthermore, FY1 modification increased the PCE of PSC modules with an active area of 14 cm2 to 21.8 %; after continuous illumination for 850 h, it retained approximately 98.5 % of the initial efficiency. These findings show that FY1 can assist in unlocking the full potential of this emerging photovoltaic technology. [ABSTRACT FROM AUTHOR]

[Display omitted] • Conjugated polyelectrolyte was developed and used as a dopant in PSCs. • PPNNA doping improves the formation of the perovskite film. • PPNNA doping realizes efficient surface passivation and electron extraction. • PPNNA can significantly enhance device performance and stability. Perovskite solar cells (PSCs) have achieved great success in the past few years because of outstanding photovoltaic performance. However, the existence of electronic trap states in the perovskite film is an obstacle for the fabrication of high-performance and stable PSCs. Herein, a linear conjugated polyelectrolyte was developed and employed as a dopant to improve the performance and stability of the perovskite film. The PPNNA doping can passivate surface defects to reduce the electronic trap states in the perovskite film, while simultaneously enhancing the electron extraction and transport to achieve high-efficiency solar cells. Furthermore, the PPNNA-doped perovskite film shows better stability from efficient surface passivation. The optimal 0.4% PPNNA-doped device exhibits better photovoltaic efficiency (20.38%) with enhanced device stability as compared to the control device (18.51%). This novel method by doping with the conjugated polyelectrolyte provides a pathway to fabricate high-efficiency and stable inverted PSCs. [ABSTRACT FROM AUTHOR]

A novel perovskite film post-treatment method, denoted high-pressure cooking (HPC) process, was developed to prepare perovskite films with ultra-flat surface, highly ordered perovskite grains, and large grain distribution. The inverted PSC with HPC treatment achieved an excellent PCE of 23.07% with remarkably high light-operation stability. [Display omitted] • A novel post-treatment method was developed to optimize perovskite films. • Ultra-flat, highly ordered and large grain distribution were achieved. • A fascinating method FRAP was conducted to study the light stability. • The PSC with HPC treatment shows high light-operation stability. • The inverted PSC with HPC treatment achieved an excellent PCE of 23.07%. High-quality perovskite absorber is the basis for obtaining high-performance perovskite solar cells (PSCs). Herein, a novel perovskite film post-treatment method, called high-pressure cooking (HPC) process, was developed to prepare ultra-flat perovskite films, with highly ordered perovskite grains and monolayer structures. The various carrier dynamic characterizations indicated high-quality perovskite grains from HPC treatment contributing to the improvement of transmission speed and collection efficiency of the photogenerated carriers, as well as reducing the defects assisted recombination loss. As a result, the inverted PSC with HPC treatment achieved an excellent PCE of 23.07% with fully optimized photovoltaic performance parameters. Furthermore, fluorescence recovery after photobleaching (FRAP) measurements suggested large grain size by HPC treatment to possess better resistance to halide-ion movement and photochemical decomposition. Among samples, HPC PSC possessed remarkably high light-operation stability at maximum power output coupled with long-term stability when stored in air condition. [ABSTRACT FROM AUTHOR]

• HPDT is developed as an interface material in perovskite solar cells. • HPDT shows suitable energy levels and high electron mobility. • HPDT can achieve a homogeneous pinhole-free PCBM layer. • The PSC performance is improved with negligible hysteresis and enhanced stability. Fullerene derivatives are promising electron transporting materials for low-temperature processed inverted perovskite solar cells (PSCs). However, fullerene derivatives have some disadvantages, e.g. [6,6]-phenyl C 61 butyric acid methyl ester (PCBM) has unmanageable morphology, low electron mobility and easily generated non-radiative recombination, which restrict the performance of PSCs. Herein, a novel n-type small organic molecule, homologous perylene diimide tetramer (HPDT), is designed and synthesized in this work to engineer the interface properties by enhancing interface contact, decreasing energetic barrier and recombination losses. HPDT shows suitable energy levels and high electron mobility and thus will increase the electron mobility during interface engineering in the inverted PSCs. Moreover, coating HPDT on top of perovskite prior to the deposition of PCBM is helpful to achieve a homogeneous pinhole-free PCBM layer, leading to enhanced power conversion efficiency from 17.38% up to 19.75% for inverted MAPbI 3 PSCs along with a negligible hysteresis. Significantly, our results undoubtedly provide new guidelines in exploring n-type organic small molecules for high-performance PSCs. [ABSTRACT FROM AUTHOR]