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Optimizing the organic solar cell efficiency: Role of the active layer thickness

APAYDIN, Dogukan Hazar
Yildiz, Dilber Esra
Çırpan, Ali
Toppare, Levent Kamil
A 2-dodecyl benzotriazole and 9,9-dioctylfluorene containing alternating conjugated polymer, poly((9,9-dioctylfluorene)-2,7-diyl-(4,7-bis(thien-2-yl) 2-dodecyl-benzo[1,2,3]triazole)) (PFTBT), was blended with PCBM (1:1, w/w) and spin coated on ITO substrates using varying rotational speeds to obtain different active layer thicknesses. J-V characteristics of the constructed devices were investigated both in dark and under simulated sunlight (AM 1.5G, 100 mW/cm(2)). For the determination of hole mobilities the space charge limited current (SCLC) method was used and found as 1.69 x 10(-6) cm(2)/Vs. In addition, the power conversion efficiency (PCE) of the devices was varied according to active layer thickness and the best power conversion efficiency was recorded as 1.06%. Moreover, incident-photon-to-current-efficiency (IPCE) measurements were carried out and the best efficiency was found to be 51%. Morphology of the active layers was probed using AFM and TEM techniques.