The Study Of Carrier Transport Properties And Interface Of Inverted Small-Molecule Organic Photovoltaic Cells

Today, the environment pollution and energy shortage are afraid by many people. Therefore, a lot of researchers focus on solar cells over the past decade, especially organic photovoltaic(OPV). OPV are gaining recognition for their substantial potential in large-area, flexible, inexpensive, low-cost renewable power generation and light-weight.At First, the contribution OPV are optimized by two methods: adding to a additional cathode modified layer and using three donor layers. The structures for the fabricated two cathode buffer layer OPV are as follows: ITO/MoO3(10nm)/ZnPc(10nm) /C60(34nm)/BCP(10nm)/PTCBI(0,2,8,10nm)/Ag(100nm). This device was measured resulting in the following device parameters: the VOC increases from 0.43 V to 0.48 V, JSC=7.92mA/cm2, FF=44.11% and PCE=1.68% in the devices with 8nm. The PTCBI layer can decrease the electron density in C60, and suppresses polaron induced exciton quenching through solving the strong dipole(0.9eV) at the C60/BCP contact.Secondly, Using the structures: ITO/MoO3(10nm)/Rubrene(5nm)/SubPc:Pentacene(7nm)/ZnPc(5nm)/C60(34nm)/Bphen(5nm)/Ag, the mix proportion of SubPc and Pentacene for 10:1, 3:1, 1:1, 1:3, we obtion the device parameters: VOC=0.84 V,JSC=9.92mA/cm2,FF=30.11%。PCE=2.53%, higher than the monolayer 322% and the bilayer 58%. The different absorption spectrum of triple donor layer is beneficial to improving the absorption efficiency of device. Furthemore, excitons can dissociate at each intermediate donor interface. The effect of Rubrene is block exciton where quenching can occur. The carrier mobility of SubPc is improved by doping the pentacene. Therefore, the performance of the device increases, finally.In the end, The structures for the fabricated inverted OPV are as follows: ITO/ C60(34nm)/ZnPc(X nm, X=10, 15, 20, 25)/MoO3(20nm)/Ag(100nm); ITO/ MoO3(10nm)/ZnPc(Y nm,Y=10,15,20,25)/C60(34nm)/Bphen(10nm)/Ag(100nm). It can be seen that while VOC decrease 17% because of the different interface roughness, the max JSC of the inverted OPV devices increase 46%, and the maximum FF improve 37%, Finally, a maximum power conversion efficiency(PCE)is 2.03 % in the inverted devices with 20 nm, increasing 65%. Analysis revealed the ability of MoO3 to reflecting excitons taking the place of quenching excitons when deposition order changing, as well as a Schottky junction between the C60 and ITO by cancelling the Bphen, resulting in a cascade device.Except from that, the exciton diffusion lenth also increase. Three material Pentacene, Rubrene and SubPc are applied in the inverted structure additionally.Nnfortunately, only SubPc succeed, and the experiment demonstrates not all material can apply in the inverted structures.