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New Conjugated Polymers Based on Dithieno[2,3‐e:3′,2′‐g]Isoindole‐7,9(8H)‐Dione Derivatives for Applications in Nonfullerene Polymer Solar Cells
摘要： We have designed two new wide bandgap A1-D1-A2-D1 conjugated polymers with same dithieno[2,3-e:3’,2’-g]isoindole-7,9(8H)-dione (DTID) acceptor (A1) and D1 (thiophene donor) and different A2 acceptor units i.e. benzothiadiazole (BT) and fluorinated benzothiadiazole (f-BT) denoted as P113 and P114 and investigated the effect of fluorination the benzothiadiazole acceptor unit on photovoltaic properties of polymer solar cells using non-fullerene acceptor. We found that the incorporation of fluorine atom into the benzothiadiazole acceptor unit increases the absorption coefficients and the relative dielectric constant. The increase in the photoluminescence quenching, reduction in charge recombination loss and improvement in the charge carrier life are observed for the P114. These all factors resulted in dramatically improved the power conversion efficiency of P114:ITIC-m based polymer solar cell to 10.42 % with small energy loss of 0.56 eV as compared to P113 counterpart (8.74 % with energy loss of 0.69 eV) under identical conditions. The low energy loss is beneficial to overcome the trade-off between open circuit voltage and short circuit current.
关键词： low energy loss,dielectric constant,Polymer solar cells,power conversion efficiency,fluorinated backbone
更新于2025-09-12 10:27:22
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Rational Design of Low Bandgap Polymers for Efficient Solar Cells with High Open-Circuit Voltage: The Profound Effect of Me and Cl Substituent with Similar Van Der Waals Radius
摘要： Generally, low bandgap materials-based photovoltaic devices have reduced open circuit voltage (VOC), and how to realize the trade-off between the low bandgap (Eg<1.6 eV) and high VOC (>0.9 V) could be critical to give efficient polymer solar cells, especially for high-performance semitransparent PSCs and tandem solar cells. Although lots of efforts have been made to address the issue, most results may be not gratifying. In this work, the polymer PTBTz-Cl based on the chlorination method and efficient thiazole-induced strategy was designed and synthesized, aiming at the deep HOMO energy level, and the enhanced backbone planarity caused by the weak noncovalent Cl···S interaction. In addition, the methyl-substituted polymer PTBTz-Me was constructed as the reference due to the similar van der Waals radius of side chain (CH3: 0.20 nm vs Cl: 0.18 nm). Encouragingly, in comparison with that of PTBTz-2, the newly synthesized polymers exhibit the red-shifted absorption spectra ranging from 300 to 770 nm, with obviously reduced Eg of ～1.6 eV. However, the function of Cl and Me substituent is different. Compared to the polymer PTBTz-Me, PTBTz-Cl exhibits a lower HOMO value, stronger crystallinity, and more compact intramolecular interactions. Consequently, the polymer PTBTz-Cl exhibits excellent photovoltaic performance with a notable VOC of 0.94 V and a PCE of 10.35%, which is ～11% higher than the 9.12% efficiency based on PTBTz-Me, and is also one of the highest values among polymer/fullerene solar cells. Moreover, a smaller photo energy loss (Eloss) of 0.64 eV is achieved, which is rare among the current high-performance polymer systems.
关键词： High open-circuit voltage,Low energy loss,Photovoltaic performance,Chlorination method,Polymer solar cell
更新于2025-09-11 14:15:04