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.…”

Thiophene with Oligoethylene Oxide Side Chain Enables Random Terpolymer Acceptor to Achieve Efficient All‐Polymer Solar Cells

“…[1][2][3][4][5][6] Since the rapid updates of polymer and small molecule material, the highest power conversion efficiency (PCE) of single junction heterojunction (BHJ) PSCs has exceeded 18 %. [7][8][9][10][11] Compared with small molecule materials, polymer materials have better intrinsic stability, higher mechanical stability and more suitable for printed fabrication, therefore, allpolymer solar cells (all-PSCs) consisting of p-type polymer donors and n-type polymer acceptors have attracted more and more attention and research from different research groups. [12][13][14][15][16] Thanks to the tremendous efforts, such as optimization of molecular weight, [17,18] random copolymerization, [19][20][21] and optimization of deposition techniques, [22,23] many high efficiency devices have been widely reported, and the optimal PCE of all-PSCs has been improved to more than 15 %.…”