The improved performance of solution-processed SQ:PC_(71)BM photovoltaic devices via MoO_3 as the anode modification layer

摘要

The enhanced performance of a squaraine compound, 2,4-bis[4-(N,N-diisobutylamino)-2,6-dihydroxyphenyl] squaraine (SO) as a donor, and [6,6]-phenyl-C71-butyric acid methyl ester (PC_(71)BM) as an acceptor in solution processed organic photovoltaic devices (OPVs) via the anode modification and thermal annealing is investigated. Through the optimization of these two factors, a maximum power conversion efficiency (PCE) of 4.08& under AM 1.5 G illumination (100mW/cm~2) is obtained. The results show that poly (3,4-ethylenedioxythiophene):poly (styrenesulfonicacid) (PEDOT:PSS) deteriorates the performance of SQ:PC_(71)BM based OPVs, and MoO_3 is used to substitute PEDOT:PSS as an effective exciton-blocking layer. A higher open-circuit voltage (V_(OC)) of 0.95 V is reached. The barrier matching between the energy-level of MoO_3 and HOMO of SQ enhances fill factor (FF) and short-circuit current density (J_(SC))- The operation mechanism of the thermal annealing is also straightened out. The higher carrier mobility and improved contact is obtained under 70 ℃ annealing, which results from the higher nanoscale crystallinity and the optimal scale phase separation between donor-acceptor networks. Hence the balanced charge carrier mobility increases the FF and PCE of OPVs by decreasing the charge recombination.