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A donor-acceptor dyad system involving tetrathiafulvalene (TTF) as donor attached by a flexible spacer to perylene-3,4:9,10-bis(dicarboximide) (PDI) as acceptor was synthesized and characterized. The strategy used the preliminary synthesis of an unsymmetrical PDI unit bearing an alcohol functionality as anchor group. Single-crystal analysis revealed a highly organized arrangement in which all PDI molecules are packed in a noncentrosymmetrical pattern. It was shown that the fluorescence emission intensity of the TTF-PDI dyad can be reversibly tuned depending on the oxidation states of the TTF unit. This behavior is attributed to peculiar properties of TTF linked to a PDI acceptor, which fluoresces intrinsically. Consequently, this dyad can be considered as a new reversible fluorescence-redox dependent molecular system.

A series of perylene‐3,4:9,10‐bis(dicarboximide) (PBI) and perylene‐3,4:9,10‐bis(benzimidazole) (PTCBI) derivatives that are di‐ or tetra‐substituted at the bay region by electron‐donating or electron‐withdrawing groups have been synthesized as soluble n‐type semiconductors. Optical absorption spectroscopy and electrochemical analysis show that the nature of substitution at the bay region plays a crucial role in the modulation of the electronic properties of these PBI and PTCBI derivatives. Examination of these optical and electrochemical data in the light of energy levels identified by theoretical studies allowed a relationship between the structure and the electronic properties to be established.

The stability of perovskite solar cells (PSCs) is currently a hot topic, but the investigation as well as the understanding of the degradation mechanisms remain incomplete. We present the intrinsic degradation mechanisms of a traditional monocation perovskite in photovoltaic devices performed with various electron transport layers (ETLs). The monocation perovskite material is a Cl-doped CH 3 NH 3 PbI 3 system, known to provide a favorable morphology leading to improved efficiency. With the long-term view of developing low-temperature processes for PSCs, two emerging ETLs compatible with TiO 2 substitution were chosen in order to study both the initial perovskite state and performance, along with their stability after aging. Aluminumdoped zinc oxide (AZO) and tin oxide (SnO 2 ) were thus selected and placed as the ETL in a planar NIP solar cell architecture, leading to different n-type substrates that can imply deviations in the formation and/or degradation of the perovskite layer. As a result, the overall performance and stability for the designed devices were strongly impacted using AZO as compared to SnO 2 . A detailed investigation using complementary characterization techniques helped in the understanding of the initial compositions and morphologies of the perovskite according to the underlying ETL layer used and their unalike evolution during mild aging conditions (inert atmosphere, dark, 35 °C). Infrared spectroscopy, X-ray diffraction, UV−visible absorption, photoluminescence, scanning electron microscopy, and current−voltage characteristics brought a new understanding of the local degradation mechanisms and their consequences on the macroscopic functional properties of PSC devices. Two different degradation mechanisms specific to the ETL have been distinguished. The ETL nature controls the perovskite microstructure and thereby the performance and stability of the complete device.

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In the field of photovoltaics, perovskite solar cells have attracted great interest due to their high efficiency combined with a strong potential for low cost and good versatility. One of the main issues concerns the intrinsic stability of these cells. To develop mitigation strategies, there is a critical need for a better understanding of the most plausible degradation mechanisms. This work focuses on the impact of the hole transporting layer (HTL) on the stability of planar NIP perovskite solar cells based on MAPbI 3-x Cl x . From the comparison of two different HTLs (P3HT and PTAA), the crucial role of interfacial materials on the stability of a complete device is demonstrated. Even if PTAA-based devices presented better performances in the initial state, their degradation under mild aging conditions (35 °C, under dark and inert conditions) is more pronounced than that with the P3HT counterpart. Thanks to complementary characterization tools (infrared spectroscopy, X-ray diffraction, UV−visible absorption, and photoluminescence) applied to different stages of the stack assembly (with respectively three, four, or five layers), a degradation mechanism was identified at the perovskite−PTAA interface. These devices consist of several extremely thin layers; the interfaces play an important role on the performances and stability of the complete cells. It is a pioneering work in the community, which could be transposed to other devices and architectures.

This Article first addresses the need for intrinsic electroluminescence and photoluminescence imaging characterizations. Both are always performed in arbitrary units preventing system comparisons as a function of chemistry, processing, aging time, or between different authors. We propose a simple equation to extract the intrinsic contribution of the sample in a broad range of measurement conditions. This work will enable authors to vary the measurement features to optimize the outcomes in resolution/saturation for photonic characterization. This method will also help model the electroluminescence and photoluminescence mechanisms with quantitative data. It should therefore be possible to carry out a much broader and systematic study to help the future development of solar cells. The developed quantification method was applied to organic and perovskite solar cells. According to the selected analysis, filters must be added to isolate the photovoltaic mechanisms coming from the active layer itself from that of the active layer–electrode interfaces. It was even possible to compare the organic and perovskite technologies and, thereby, better appreciate their functioning principle and its impact on the overall photovoltaic performances.

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