Performance Improvement Of Organic Solar Cells Based On Rubrene/C₇₀ With Heat Treatment And Cathode Modification

Because of the advantages on fabricating method, producing cost, flexible-substrate and large-fabrication, the organic solar cells(OSCs) has become a hot research spot. Though the power conservation efficiency(ηP) of single heterojunction devices has transcended 9%, it is still far away to be used used in commercial application. In this thesis, OSCs based on Rubrene/C70 with the structure of PN and PIN were fabricated. The article was focused on three aspects as follow.1. OSCs based on Rubrene/C70 with the structure of PN and PIN were fabricated. The effect of heat treatment on the performance of two cells was researched by thermal annealing.The results showed that the short-circuit current were up to 3.526 m A·cm-2(PN) and 5.413 m A·cm-2(PIN), and the power conservation efficiency of these cells were as high as 1.43%(PN)and 2.09%(PIN)with thermal annealing. Compared with the devices without thermal annealing,short-circuit current(JSC), fill factor(FF) and the power conservation efficiency(ηP) of PN/PIN cells were enhanced. Heat treatment led the active layers to crystallization, and therefore the carrier mobility of OSCs was improved. Furthermore, the area of the heterojunction was increased by thermal annealing, the efficiency of the exciton dissociation was enhanced and the performance of OSCs was improved.2. Organic solar cells(OSCs) with the structure of ITO/ Mo O3(6 nm)/ Rubrene(30 nm)/C70(30 nm)/ PTCBI(x nm)/ Al(150 nm) were fabricated. Role of perylenebisimide with extended pi system(PTCBI) cathode modified layer in Rubrene/C70 based organic solar cells was investigated. Experimental results show that the insertion of PTCBI between C70 and Al electrode can significantly improve the performance of devices. PTCBI constitutes an Ohmic contact between C70 layer and Al cathode, promotes built-in potential in OSCs. Further, PTCBI not only obstructs the excitons and Al electrode contact, but also preserved C70 from high energy Al in the cathode preparation process. The effect of PTCBI thickness on the performances of OSCs was researched as well, The results indicate that the optimized PTCBI thickness is 6 nm and the open circuit voltage(VOC), fill factor(FF), short current density(JSC), power conservation efficiency(ηP) of the optimum device are enhanced. Compared with the OSCs without PTCBI,performance of the optimum devices are ameliorated by 70.4%, 55.5%, 125.1%, 292.2%,respectively.3. The degradation of cells was investigated completely. The relationship between time and performance of OSCs was investigated by the J-V characteristics test every once in a while. The results show that the VOC was invariable. Nonetheless, The JSC, ηP declined continuously over time. Roles of oxygen and water were speculated to be the significant factor led to degradation of OSCs. Chemical reactions on the interface between organic material and metal electrode led to delamination, which caused the performance of OSCs to decrease. Therefore, OSCs should be packaged.