Functional Modification Of Graphene And The Development Of Graphene-based Organic Solar Cells

During the past several years,organic solar cells?OSCs?have received wide attention for solar energy utilization due to their competitive advantages,including low-cost,flexibility,portability and lightweight.Typical OSCs are composed of a photoactive layer,interfacial layers,and electrodes.The device performance can be substantially affected by interfacial layers,which can effectively promote charge extraction and light transmission.However,many interfacial layers are high-cost due to multi-step synthesis and poor stability,which can restrict the commercialization of OSCs.Herein,there is a great challenge for us to design solution-processable,low cost,high efficient,and high stable OSCs.As a new emerging two-dimensional?2D?nanomaterial,graphene possesses outstanding physical and chemical properties,including high carrier mobility,high specific surface area and high optical transparency,which make graphene have significant potential in interface modification of OSCs.In this work,we prepared graphene-based materials as interface layer?including electron transport layer and hole transport layer?from the perspective of interface materials of organic solar cell devices,which improve photoelectric conversion efficiency and device stability of OSCs.Details are summarized as follws:1.Interface modification of OSCs using solution-processed functionalized reduced graphene oxide as electron transport layer:In this work,we report a new solution-processed functionalized reduced graphene oxide?FGr?as an efficient stable electron transport layer for high-efficiency OSCs.The highly dispersed FGr was obtained through introducing vinyl group and Si–O–Si groups on graphene surface by VTES,which can connect graphene to form network structure.Power conversion efficiency?PCE?of FGr-based devices(9.47%?4.05%and 8.01%for PTB7-Th:PC₇₁BM,P3HT:PC₇₁BMandPBDT-BDD:PC₇₁BM,respectively)outperform PFN-based devices?8.94%,3.52%and 7.8%,respectively?.And,the stability of the devices was improved with FGr as electron transport layer compared to PFN.The PCE of FGr-based devices maintain 92.6%after 61 days?56.5%for PFN-based devices?.The conclusions indicate that FGr is a promising electron transport layer material for high-performance and stable OSCs.2.Interface modification of OSCs using solution-processed graphene oxide as hole transport layer:In this work,the graphene oxide?GO?was synthesized by simple Hummers method and oxygen plasma treatment was conducted on GO thin films.PCEs of FGr-based devices(7.97%and 9.02%for PBDT-BDD:PC₇₁BM and PTB7-Th:PC₇₁BM,respectively)are comparable with PEDOT:PSS-based devices?7.9%and 9.18%,respectively?.The stability of the devices was improved with GO as hole transport layer compared to PEDOT:PSS.The PCE of GO-based devices preserved 83%of original values after storage for 80 days,while the PCE of PEDOT:PSS-based devices decreased to 45%.These conclusions indicate that GO is a promising hole transport layer material,thus further promoting the realization of high stability and low-cost OSCs.In addition,these results indicate that OSCs technology is a step closer towards being an all solution-processed technology.