Understanding photochemical degradation mechanisms in photoactive layer materials for organic solar cells

Over the past decades, the field of organic solar cells (OSCs) has witnessed a significant evolution in materials chemistry, which has resulted in a remarkable enhancement of device performance, achieving efficiencies of over 19%. The photoactive layer materials in OSCs play a crucial role in light absorption, charge generation, transport and stability. To facilitate the scale-up of OSCs, it is imperative to address the photostability of these electron acceptor and donor materials, as their photochemical degradation process remains a challenge during the photo-to-electric conversion. In this review, we present an overview of the development of electron acceptor and donor materials, emphasizing the crucial aspects of their chemical stability behavior that are linked to the photostability of OSCs. Throughout each section, we highlight the photochemical degradation pathways for electron acceptor and donor materials, and their link to device degradation. We also discuss the existing interdisciplinary challenges and obstacles that impede the development of photostable materials. Finally, we offer insights into strategies aimed at enhancing photochemical stability and discuss future directions for developing photostable photo-active layers, facilitating the commercialization of OSCs.

Asymmetric non-fullerene acceptors enable high photovoltaic performance via the synergistic effect of carbazole-terminated alkyl spacer and halogen substitution

A novel design approach of asymmetric NFA via synergetic alkyl spacer length and halogen substitution enables high photovoltaic performance.

Recent Progress in Indacenodithiophene-Based Acceptor Materials for Non-Fullerene Organic Solar Cells

Domesticating solar energy by exploiting photovoltaic technology has become a quintessential strategy for future global energy production. Since 2015, non-fullerene organic solar cells (NF-OSC) have attracted a great deal of attention owing to the marvellous properties of non-fullerene acceptors (NFA) such as structural versability, broad absorption, suitable energy levels, tunable charge transport and morphology, leading to remarkable accomplishments in power conversion efficiency (PCE) from 1% to nearly 20%. One class of materials is provided by the fused ring aromatic indacenodithiophene (IDT) and its derivatives, which are emerging continuously as promising next-generation building blocks to construct high performance photovoltaic materials. Encouraging PCEs of more than 15% have been achieved in their binary NF-OSCs, while careful device engineering and proper amalgamation of a third component have led to PCEs of almost 18% in ternary devices. This review surveys recent developments in the area of IDT-based materials for photovoltaic applications. Different strategies to develop efficient IDT-based NFA and factors influencing the bandgaps, molecular energy levels, charge transport properties, and film morphologies, as well as the photovoltaic performance of these materials, are discussed.