Polymerized Small Molecular Acceptor with Branched Side Chains for All Polymer Solar Cells with Efficiency over 16.7%

Abstract

The power conversion efficiencies (PCEs) of small molecule acceptor (SMA)‐based organic solar cells have already exceeded 18%. However, the development of polymer acceptors still lags far behind their SMA counterparts mainly due to the lack of efficient polymer acceptors. Herein, a series of polymer acceptors named PY‐X (with X being the branched alkyl chain) are designed and synthesized by employing the same central core with the SMA L8‐BO but with different branched alkyl chains on the pyrrole motif. It is found that the molecular packing of SMA‐HD featuring 2‐hexyldecyl side chain used in the synthesis of PY‐HD is similar to L8‐BO, in which the branched alkyl chains lead to condensed and high‐order molecular assembly in SMA‐HD molecules. When combined with PM6, PY‐HD‐based all polymer solar cell (all‐PSC) exhibits a high PCE of 16.41%, representing the highest efficiency for the binary all‐PSCs. Moreover, the side‐chain modification on the pyrrole site position further improves the performance of the all‐PSCs, and the PY‐DT‐based device delivers a new record high efficiency of 16.76% (certified as 16.3%). The work provides new insights for understanding the structure–property relationship of polymer acceptors and paves a feasible avenue to develop efficient conjugated polymer acceptors.

An efficient polymer acceptor via a random polymerization strategy enables all-polymer solar cells with efficiency exceeding 17%

“…16–19 The recent success of Y-series SMAs has accelerated the development of PSMAs and a few representative PSMAs with PCEs over 16% have been reported. 20–22 In the pioneering attempts of molecular optimization, much effort has been focused on the modifications of the SMA main building block, 23 fluorinated end group, and π-bridge. 24–26 Besides these approaches, the random copolymerization comprising three or more functional units in the backbone which can integrate the complementary advantages of each chromophore appears to be a very promising and feasible synthetic strategy for fine-tuning the optical and electronic properties of polymer acceptors.…”

“…In our recent work, we reported an efficient polymer acceptor named PY-DT by modifying the beta position of the thiophene unit core with branched alkyl chains. 22 It was shown that the branched alkyl chain modification of SMA-DT could lead to upshifted lowest unoccupied molecular orbital (LUMO) energy levels and blue-shifted absorption spectra, and thereby an improved open-circuit voltage ( V oc ) of 0.949 V in the related photovoltaic device. Nevertheless, because of the blue-shifted absorption, the short-circuit current density ( J sc ) of the PY-DT-based all-PSC is limited to 23.40 mA cm −2 .…”

Regioisomeric Polymer Semiconductors Based on Cyano-Functionalized Dialkoxybithiophenes: Structure–Property Relationship and Photovoltaic Performance

“…Both higher short-circuit current density (J sc ) and fill factor (FF) values are responsible for a higher PCE for PBDTBT HH . Several solvent additives were also tested for further device optimization [60,61]. The addition of 2 vol% 1-chloronaphthalene (CN) resulted in clearly improved photovoltaic performance.…”

Realizing the efficiency-stability balance for all-polymer photovoltaic blends

“…31–33 In recent years, the new types of polymerized small molecular acceptors endow the polymer–polymer device with a rapid increase in PCE. 34–48 However, this type of all-polymer blend exhibits a poorer stability due to the low molecular weight. Accordingly, material designs based on current, mature, efficient all-polymer systems aiming to promote the stability of the morphology should be a meaningful strategy.…”