Charge Carrier Trapping in Organic Solar Cell Structures P3HT:PCBM

We have investigated carrier transport and trapping in blends of 6:5 wt. P3HT:PCBM that are important for the development of organic Solar cells. The devices with the inverted layer sequence and solar efficiency of 3.7% were analysed. We demonstrate that, though the fill factor of the IV characteristics is as high as 68%, carrier trapping is effectively involved in the transport phenomena. The evaluated trapping state activation energy is about 0.18 eV and their density is up to 1020 ÷ 7 × 1021 cm−3. At such high density these states may probably act as transport states, limiting carrier mobility. The results were analyzed by taking into account mobility variation according to the Gaussian disorder model as well as carrier thermal generation from traps. The mobility parameters obtained by both methods demonstrate good coincidence.