Review of roll-to-roll fabrication techniques for colloidal quantum dot solar cells

Colloidal quantum dots(CQDs)are of great interest to photovoltaic(PV)technologies as they possess the benefits of solution-processability,size-tunability,and roll-to-roll manufacturability,as well as unique capabilities to harvest near-infrared(NIR)radiation.During the last decade,lab-scale CQD solar cells have achieved rapid improvement in the power conversion efficiency(PCE)from~1%to 18%,which will potentially exceed 20%in the next few years and approach the performance of other PV technologies,such as perovskite solar cells and organic solar cells.In the meanwhile,CQD solar cells exhibit long lifetimes either under shelf storage or continuous operation,making them highly attractive to industry.However,in order to meet the industrial requirements,mass production techniques are necessary to scale up the fabrication of those lab devices into large-area PV modules,such as roll-to-toll coating.This paper reviews the recent developments of large-area CQD solar cells with a focus on various fabrication methods and their principles.It covers the progress of typical large-area coating techniques,including spray coating,blade coating,dip coating,and slot-die coating.It also discusses next steps and new strategies to accomplish the ultimate goal of the low-cost large-area fabrication of CQD solar cells and emphasizes how artificial intelligence or machine learning could facilitate the developments of CQD solar cell research.

Low-Temperature Aging Provides 22% E cient Bromine-Free and Passivation Layer-Free Planar Perovskite Solar Cells

Previous reports of formamidinium/methylamine(FAMA)-mixed halide perovskite solar cells have focused mainly on controlling the morphology of the perovskite film and its interface—for example,through the inclusion of bromine and surface passivation.In this paper,we describe a new processing pathway for the growth of a high-quality bromine-free FAMAPbI3 halide perovskites via the control of intermediate phase.Through low-temperature aging growth(LTAG)of a freshly deposited perovskite film,α-phase perovskites can be seeded in the intermediate phase and,at the same time,prevent beta-phase perovskite to nucleate.After postannealing,large grain-size perovskites with significantly reduced PbI2 presence on the surface can be obtained,thereby eliminating the need of additional surface passivation step.Our pristine LTAG-treated solar cells could provide PCEs of greater than 22%without elaborate use of bromine or an additional passivation layer.More importantly,when using this LTAG process,the growth of the pure alpha-phase FAMAPbI3 was highly reproducible.

Review and perspective of materials for flexible solar cells

Thin-film flexible solar cells are lightweight and mechanically robust.Along with rapidly advancing battery technology,flexible solar panels are expected to create niche products that require lightweight,mechanical flexibility,and moldability into complex shapes,such as roof-panel for electric automobiles,foldable umbrellas,camping tents,etc.In this paper,we provide a comprehensive assessment of relevant materials suitable for making flexible solar cells.Substrate materials reviewed include metals,ceramics,glasses,and plastics.For active materials,we focus primarily on emerging new semiconductors including small organic donor/acceptor molecules,conjugated donor/acceptor polymers,and organometal halide perovskites.For electrode materials,transparent conducting oxides,thin metal films/nanowires,nanocarbons,and conducting polymers are reviewed.We also discuss the merits,weaknesses,and future perspectives of these materials for developing next-generation flexible photovoltaics.

Highly Conductive Zinc-Tin-Oxide Buffer Layer for Inverted Polymer Solar Cells

Thin-films of Zinc Tin Oxide(ZTO)with an extremely high charge carrier mobility and superior optical transmittance are synthesized using a simple solution method.These ZTO films have been systematically studied for the application in inverted polymer solar cells(PSCs).The Hall effects measurements show that the charge