Interfacial Materials for Organic Solar Cells: Recent Advances and Perspectives

Abstract

Organic solar cells (OSCs) have shown great promise as low‐cost photovoltaic devices for solar energy conversion over the past decade. Interfacial engineering provides a powerful strategy to enhance efficiency and stability of OSCs. With the rapid advances of interface layer materials and active layer materials, power conversion efficiencies (PCEs) of both single‐junction and tandem OSCs have exceeded a landmark value of 10%. This review summarizes the latest advances in interfacial layers for single‐junction and tandem OSCs. Electron or hole transporting materials, including metal oxides, polymers/small‐molecules, metals and metal salts/complexes, carbon‐based materials, organic‐inorganic hybrids/composites, and other emerging materials, are systemically presented as cathode and anode interface layers for high performance OSCs. Meanwhile, incorporating these electron‐transporting and hole‐transporting layer materials as building blocks, a variety of interconnecting layers for conventional or inverted tandem OSCs are comprehensively discussed, along with their functions to bridge the difference between adjacent subcells. By analyzing the structure–property relationships of various interfacial materials, the important design rules for such materials towards high efficiency and stable OSCs are highlighted. Finally, we present a brief summary as well as some perspectives to help researchers understand the current challenges and opportunities in this emerging area of research.

Surface passivation effect by fluorine plasma treatment on ZnO for efficiency and lifetime improvement of inverted polymer solar cells

“…In this regard, many studies have focused on engineering the surface of ZnO films through improving the interfacial electrical properties, better aligning energy-level and controlling the surface energy. Among the most efficient methods to modify the ZnO surface are the ultraviolet (UV) or UV-ozone treatment, [32][33][34][35][36][37] and the incorporation of a surface modification interlayer, such as a coordination polymer 38,39 or a self-assembled monolayer (SAM). [40][41][42][43][44] However, UV treatment may cause severe degradation of the device lifetime whereas the insulating properties of coordination polymers results in a trade-off between effective passivation and charge transport.…”

Controlled self-aggregation of perylene bisimide and its application in thick photoconductive interlayers for high performance polymer solar cells

“…Zinc oxide (ZnO) is a widely used cathode interlayer material in inverted PSCs with advantages like high transparency, low-cost, easy solution procession, and proper energy levels, which is usually fabricated through a so called "sol-gel" method. [16][17][18] Amorphous thin film derived by this method shows rather low electron mobility in the level of 10 -3 -10 -4 cm 2 V -1 s -1 due to plenty of defects as electron trapping sites, and shows rather low electron conductivity. 17 Various methods have been applied to increase the conductivity of ZnO thin film, including elements doping such as aluminum doped ZnO (AZO), 19 gallium doped ZnO (GZO), 20 indium doped ZnO (IZO) 21 and tin doped ZnO (ZTO).…”

Improved Stability of Polymer Solar Cells in Ambient Air via Atomic Layer Deposition of Ultrathin Dielectric Layers

“…[1,2] Presently, PSCs based on interpenetrating donor:acceptor networks exhibit power conversion efficiencies (PCEs) exceeding 10% for singlejunction [3,4] and 12% for tandem-junction devices consisting of stacks of individual cells with complementary absorption spectra. [5,6] However, the technology is still under development in the key area of device stability. The implementation of inverted architectures has significantly improved the stability over that of conventional architectures.…”