Solution sequential deposited organic photovoltaics:From morphology control to large-area modules

Organic optoelectronic materials enable cutting-edge,low-cost organic photodiodes,including organic solar cells(OSCs)for energy conversion and organic photodetectors(OPDs)for image sensors.The bulk heterojunction(BHJ)structure,derived by blending donor and acceptor materials in a single solution,has dominated in the construction of active layer,but its morphological evolution during film formation poses a great challenge for obtaining an ideal nanoscale morphology to maximize exciton dissociation and minimize nongeminate recom-bination.Solution sequential deposition(SSD)can deliver favorable p–i–n vertical component distribution with abundant donor/acceptor interfaces and relatively neat donor and acceptor phases near electrodes,making it highly promising for excellent device performance and long-term stability.Focusing on the p–i–n structure,this review provides a systematic retrospect on regulating this morphology in SSD by summarizing solvent selection and additive strategies.These methods have been successfully implemented to achieve well-defined morphology in ternary OSCs,all-polymer solar cells,and OPDs.To provide a practical perspective,comparative studies of device stability with BHJ and SSD film are also discussed,and we review influential progress in blade-coating techniques and large-area modules to shed light on industrial production.Finally,challenging issues are out-lined for further research toward eventual commercialization.

High-performance polymer solar cells with efficiency over 18%enabled by asymmetric side chain engineering of non-fullerene acceptors

Side-chain engineering has been considered as one of the most promising strategies to optimize non-fullerene small-molecule acceptors(NFSMAs).Previous efforts were focused on the optimization of alkyl-chain length,shape,and branching sites.In this work,we propose that asymmetric side-chain engineering can effectively tune the properties of NFSMAs and improve the power conversion efficiency(PCE)for binary non-fullerene polymer solar cells(NFPSCs).Specifically,by introducing asymmetric side chains into the central core,both of the absorption spectra and molecule orientation of NFSMAs are efficiently tuned.When blended with polymer donor PM6,NFPSCs with EH-HD-4F(2-ethylhexyl and 2-hexyldecyl side chains)demonstrate a champion PCE of 18.38%with a short-circuit current density(J_(SC))of 27.48 mA cm^(-2),an open circuit voltage(V_(OC))of 0.84 V,and a fill factor(FF)of 0.79.Further studies manifest that the proper asymmetric side chains in NFSMAs could induce more favorable face-on molecule orientation,enhance carrier mobilities,balance charge transport,and reduce recombination losses.