Non-fullerene acceptors with branched side chains and improved molecular packing to exceed 18% efficiency in organic solar cells

Abstract

2 Molecular design of non-fullerene acceptors (NFAs) is of vital importance for highefficiency organic solar cells. The branched alkyl chain modification is often regarded as a counter-intuitive approach as which may introduce undesirable steric hindrance that reduces charge transport in NFAs. Here we show the design and synthesis of a highly efficient NFA family by substituting the beta position of thiophene unit on Y6-based A-DAD-A backbone with branched alkyl chains. It was found that such modification of different alkyl chain length could completely change the molecular packing behavior of NFAs, leading to improved structure order and charge transport in thin films. Unprecedented efficiency of 18.32% (certified value of 17.9%) with a fill factor of 81.5% is achieved for single-junction organic solar cells. This work reveals the importance of branched alkyl chain topology in tuning the molecular packing and blend morphology that leads to improved organic photovoltaic performance.

Non‐Fullerene Acceptors with an Extended π‐Conjugated Core: Third Components in Ternary Blends for High‐Efficiency, Post‐Treatment‐Free Organic Solar Cells

“…Thanks to the emergence of non-fullerene small molecule acceptors (NFAs), the development of the ternary blend approach, and the optimization of interface materials they have demonstrated high power conversion efficiency (PCE), semitransparency, [1,2] and compliance with large-scale manufacturing processes. Despite reaching efficiencies above 17 %, [3][4][5][6] the penetration of this technology on the market remains low. To promote the industrial transfer of OPV devices, research efforts are still needed, in particular to improve their manufacturing and long-term stability.…”

Eliminating the Detrimental Effect of Secondary Doping on PEDOT : PSS Hole Transporting Material Performance

“…Bulk heterojunction (BHJ) organic solar cells (OSCs) have undergone an impressive progress within the last few years due to the significant innovations in non-fullerene acceptors and device craft. [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15] Over 18 % power conversion efficiency (PCE) and long-term device stability have been recorded in multiple cases. [5][6][7] Apart from the development of acceptors, interface engineering upon electrodes, that is, developing hole/electron transporting materials (HTMs/ETMs), is also a most effective strategy to further enhance the performance of OSCs to a new level.…”

Organic Solar Cells Parameters Extraction and Characterization Techniques

“…High power conversion efficiency had been achieved by incorporation of non-fullerene and small molecule acceptors, which exhibit high absorption spectrum resulting in high photocurrent [1,2]. Power conversion efficiency above 18% has been achieved in the state-of-theart device [3][4][5]. Advantages of organic solar cells such as flexibility, low production cost, transparency, and simple roll-to-roll production techniques make it a promising technology for energy conversion that may take over silicon-based technologies in the future.…”