Engineering topics
Qi, Zhenyu
Publications and source records attributed to Qi, Zhenyu.
A Chlorinated Donor Polymer Achieving High‐Performance Organic Solar Cells with a Wide Range of Polymer Molecular Weight
Abstract In the field of non‐fullerene organic solar cells (OSCs), compared to the rapid development of non‐fullerene acceptors, the progress of high‐performance donor polymers is relatively slow. The property and performance of donor polymers in OSCs are often sensitive to the molecular weight of the polymers. In this study, a chlorinated donor polymer named D18‐Cl is reported, which can achieve high performance with a wide range of polymer molecular weight. The devices based on D18‐Cl show a higher open‐circuit voltage ( V OC ) due to the slightly deeper energy levels and an outstanding short‐circuit current density ( J SC ) owing to the appropriate long periods of blend films and less ([6,6]‐phenyl‐C71‐butyric acid methyl ester) (PC 71 BM) in mixed domains, leading to the higher efficiency of 17.97% than those of the D18‐based devices (17.21%). Meanwhile, D18‐Cl can achieve high efficiencies (17.30–17.97%) when its number‐averaged molecular weight ( M n ) is ranged from 45 to 72 kDa. In contrast, the D18‐based devices only exhibit relatively high efficiencies in a narrow M n range of ≈70 kDa. Such property and performance make D18‐Cl a promising donor polymer for scale‐up and low‐cost production.
A Difluoro‐Monobromo End Group Enables High‐Performance Polymer Acceptor and Efficient All‐Polymer Solar Cells Processable with Green Solvent under Ambient Condition
Abstract In this paper, a difluoro‐monobromo end group is designed and synthesized, which is then used to construct a novel polymer acceptor (named PY2F‐T) yielding high‐performance all‐polymer solar cells with 15.22% efficiency. The fluorination strategy can increase the intramolecular charge transfer and interchain packing of the previous PY‐T based acceptor, and significantly improve photon harvesting and charge mobility of the resulting polymer acceptor. In addition, detailed morphology investigations reveal that the PY2F‐T‐based blend shows smaller domain spacing and higher domain purity, which significantly suppress charge recombination as supported by time‐resolved techniques. These polymer properties enable simultaneously enhanced J SC and FF of the PY2F‐T‐based devices, eventually delivering device efficiencies of over 15%, significantly outperforming that of the devices based on the non‐fluorinated PY‐T polymer (13%). More importantly, the PY2F‐T‐based active layers can be processed under ambient conditions and still achieve a 14.37% efficiency. They can also be processed using non‐halogenated solvent o ‐xylene (no additive) and yield a decent performance of 13.05%. This work demonstrates the success of the fluorination strategy in the design of high‐performance polymer acceptors, which provide guidelines for developing new all‐PSCs with better efficiencies and stabilities for commercial applications.
Regio‐Regular Polymer Acceptors Enabled by Determined Fluorination on End Groups for All‐Polymer Solar Cells with 15.2 % Efficiency
Abstract Polymerization sites of small molecule acceptors (SMAs) play vital roles in determining device performance of all‐polymer solar cells (all‐PSCs). Different from our recent work about fluoro‐ and bromo‐ co‐modified end group of IC‐FBr (a mixture of IC‐FBr1 and IC‐FBr2), in this paper, we synthesized and purified two regiospecific fluoro‐ and bromo‐ substituted end groups (IC‐FBr‐ o & IC‐FBr‐ m ), which were then employed to construct two regio‐regular polymer acceptors named PYF‐T‐ o and PYF‐T‐ m , respectively . In comparison with its isomeric counterparts named PYF‐T‐ m with different conjugated coupling sites, PYF‐T‐ o exhibits stronger and bathochromic absorption to achieve better photon harvesting. Meanwhile, PYF‐T‐ o adopts more ordered inter‐chain packing and suitable phase separation after blending with the donor polymer PM6, which resulted in suppressed charge recombination and efficient charge transport. Strikingly, we observed a dramatic performance difference between the two isomeric polymer acceptors PYF‐T‐ o and PYF‐T‐ m . While devices based on PM6:PYF‐T‐ o can yield power conversion efficiency (PCE) of 15.2 %, devices based on PM6:PYF‐T‐ m only show poor efficiencies of 1.4 %. This work demonstrates the success of configuration‐unique fluorinated end groups in designing high‐performance regular polymer acceptors, which provides guidelines towards developing all‐PSCs with better efficiencies.
Regio‐Regular Polymer Acceptors Enabled by Determined Fluorination on End Groups for All‐Polymer Solar Cells with 15.2 % Efficiency
Abstract Polymerization sites of small molecule acceptors (SMAs) play vital roles in determining device performance of all‐polymer solar cells (all‐PSCs). Different from our recent work about fluoro‐ and bromo‐ co‐modified end group of IC‐FBr (a mixture of IC‐FBr1 and IC‐FBr2), in this paper, we synthesized and purified two regiospecific fluoro‐ and bromo‐ substituted end groups (IC‐FBr‐ o & IC‐FBr‐ m ), which were then employed to construct two regio‐regular polymer acceptors named PYF‐T‐ o and PYF‐T‐ m , respectively . In comparison with its isomeric counterparts named PYF‐T‐ m with different conjugated coupling sites, PYF‐T‐ o exhibits stronger and bathochromic absorption to achieve better photon harvesting. Meanwhile, PYF‐T‐ o adopts more ordered inter‐chain packing and suitable phase separation after blending with the donor polymer PM6, which resulted in suppressed charge recombination and efficient charge transport. Strikingly, we observed a dramatic performance difference between the two isomeric polymer acceptors PYF‐T‐ o and PYF‐T‐ m . While devices based on PM6:PYF‐T‐ o can yield power conversion efficiency (PCE) of 15.2 %, devices based on PM6:PYF‐T‐ m only show poor efficiencies of 1.4 %. This work demonstrates the success of configuration‐unique fluorinated end groups in designing high‐performance regular polymer acceptors, which provides guidelines towards developing all‐PSCs with better efficiencies.
Tailoring non-fullerene acceptors using selenium-incorporated heterocycles for organic solar cells with over 16% efficiency
The selenium substitution strategy was applied to develop two new A′-DAD-A′-type small molecular acceptors. The resulting selenium-incorporated molecules exhibit red-shifted absorption and an enhanced photon response, leading to high device efficiencies of over 16%.
Incorporation of alkylthio side chains on benzothiadiazole-based non-fullerene acceptors enables high-performance organic solar cells with over 16% efficiency
This is the first time alkylthio chains are employed on Y6-like NFAs to achieve organic solar cells of power conversion efficiency higher than 16%.
Modulating Energy Level on an A‐D‐A′‐D‐A‐Type Unfused Acceptor by a Benzothiadiazole Core Enables Organic Solar Cells with Simple Procedure and High Performance
Unfused‐ring acceptors (UFAs) have gained considerable research attention as they offer simple chemical structures through simplified synthesis methods, which would boost the commercialization of organic solar cells (OSCs). Recently, a new small molecule acceptor (SMA) named Y6 was reported, yielding high‐performance OSCs. Herein, the Y6‐like A‐DA′D‐A framework is developed to A‐D‐A′‐D‐A‐type backbone adopted in constructing UFAs. Two new Y6‐like UFAs are synthesized within four steps and the effect of noncovalent atoms at the central electron‐deficient core on material properties and device performances is studied. It is found that the introduction of fluorine atoms can bring larger red‐shift in the absorption spectra and better aggregation of the resulting UFA film states compared with those of oxygen atoms. Interestingly, the variations in the noncovalent interaction atoms induce different intermolecular charge transfer between donors and UFAs. When blended with another economical donor, PTQ10, F substitution at the benzothiadiazole ring is more effective than O substitution, leading to the increased short‐circuit current density ( J SC ) and higher efficiency of over 12%, among the best performances of UFA‐based OSCs. This contribution demonstrates the appropriate introduction of noncovalent interaction is a promising method for tuning energy levels, absorption, and aggregation of UFAs for high‐performance OSCs.