Recent Advance in Solution‐Processed Hole Transporting Materials for Organic Solar Cells

Abstract

Solution‐processed hole transporting layers (HTLs) not only play a crucial role in realizing high performance of organic solar cells (OSCs), but also possess excellent compatibility with low‐cost and large‐area processing methods of industrialized productions. However, the number and species of HTL materials are obviously fewer than that of electron‐transporting materials, which limits the development and application of OSCs. In particular, the large energy level difference between anode and organic active layer leads to the serious energy barrier for hole collection, bringing much difficulty in developing efficient HTL materials. In this review, it is focused on the recent advances in solution‐processed HTLs in OSCs. Initially, the working mechanism, property requirement, and existing issues of solution‐processed HTLs are systematically analyzed. Afterward, the main classes of solution‐processed HTL materials are discussed, including PEDOT:PSS, conjugated polyelectrolytes (CPEs), TMOs, and others. The structure‐property relationships of solution‐processed HTL materials are analyzed, and some important design rules for such materials toward efficient and stable OSCs are presented. Finally, a brief summary is presented along with some perspectives to help researchers understanding the challenges and opportunities in this field.

Simple and Efficient Synthesis of Ruthenium(III) PEDOT:PSS Complexes for High-Performance Stretchable and Transparent Supercapacitors

“…It also features high transparency (over 90%), high conductivity (over 4000 S cm −1 ), and relatively high specific capacitance (1.18 mF cm −2 ) [20,21]. Additionally, it offers electrochemical stability and is solutionprocessable [22,23]. Several groups have reported the fabrication of transparent supercapacitors based on PEDOT:PSS.…”

Binary Organic Solar Cells with >19.6% Efficiency: The Significance of Self-Assembled Monolayer Modification

“…Organic solar cells (OSCs) have gained significant attention as promising candidates for next-generation photovoltaic technologies due to their solution-processing capability, semitransparency, and flexibility. , In recent years, significant advances have been made in the field of material design and synthesis, as well as advances in morphology tuning and interfacial engineering, all aimed at continually improving the power conversion efficiency (PCE) to approach 20%. − The active layer is vital to the PCE of OSCs, yet the interfacial layer also plays a key role in charge transport and morphology regulation. Poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) has traditionally been the predominant choice as the hole transport layer (HTL) material for conventional OSC devices, owing to its decent conductivity, optical transparency, and ease of processing. − However, its acidic and hygroscopic nature cause corrosion of indium tin oxide (ITO) electrodes, and positively charged PEDOT may react with the end groups of nonfullerene acceptors (NFAs), which can lead to the degradation of devices during operation. − Moreover, the photon incidence of the active layer is limited due to its light absorption, which also restricts the further enhancement of the photovoltaic performance . Therefore, the development of efficient and durable HTLs to overcome these drawbacks is essential to improving the OSC device performance for further commercialization.…”

Enhancing Efficiency and Photo-Stability of Organic Solar Cells via Vertical Phase Separation Morphology Induced by Surface Modification of PEDOT:PSS with Star-Shaped Benzene-Based DFTAB Additive

“…It serves to minimize energy loss in charge collection by reducing the energy barrier at the electrode-active layer interface and facilitating efficient charge transport. 15 Poly (3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PE-DOT:PSS) has traditionally been the predominant choice as the hole transport layer (HTL) material for conventional OSC devices, owing to its decent conductivity, optical transparency, and ease of coating. 16,17 However, considerable efforts have been dedicated to optimizing the structure and conductivity of PEDOT:PSS to improve the device performance.…”

“…Organic solar cells (OSCs) have gained significant attention as promising candidates for next-generation photovoltaic technologies, owing to their solution-processing capability, semitransparency, and flexibility. − Recent years have witnessed notable progress in material design and synthesis, accompanied by the advancements in morphology tuning and interfacial engineering, all aimed at continually improving power conversion efficiency (PCE) toward surpassing 19%. − While the active layer plays a central role in enhancing the PCE of OSCs, the charge transport layer is equally crucial for optimizing photovoltaic performances. It serves to minimize energy loss in charge collection by reducing the energy barrier at the electrode-active layer interface and facilitating efficient charge transport . Poly­(3,4-ethylenedioxythiophene):poly­(styrenesulfonate) (PEDOT:PSS) has traditionally been the predominant choice as the hole transport layer (HTL) material for conventional OSC devices, owing to its decent conductivity, optical transparency, and ease of coating. , However, considerable efforts have been dedicated to optimizing the structure and conductivity of PEDOT:PSS to improve the device performance .…”