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[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 naphthalene imide dimer was developed and used as an interfacial material. • 2FBT2NDI layer achieves efficient surface passivation and electron extraction. • The modified PSCs show superior photovoltaic performance (20.1%). • 2FBT2NDI could be used to obtain commercializable high-performance PSCs. How to design and synthesize interfacial engineered materials that have efficient surface passivation and electron extraction properties is an important problem in the field of optoelectronic materials. Herein, a simple naphthalene imide dimer, namely 2FBT2NDI, is developed by Stille coupling reaction with a high yield, and it is used as interface engineering material for inverted perovskite solar cells (PSCs). Owing to the existence of intermolecular interactions between MAPbI 3 and the 2FBT2NDI layer, the introduction of the interfacial layer can passivate the surface defects of perovskite film and improve interface contact. In addition, 2FBT2NDI exhibits suitable energy levels and high electron mobility because of its large linear conjugated skeleton containing two fluorine atoms, which are beneficial for electron extraction for efficient PSCs. By employing 2FBT2NDI as an interfacial layer, inverted PSCs show a maximum power conversion efficiency of 20.1%, which is over 14% higher than that of the control devices without interfacial layer (17.1%). These results highlight that the naphthalene imide dimer can potentially be used as a commercializable interfacial material for achieving high-performance PSCs. [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]