Effect of defect states on CH3NH3PbI3 solar cell efficiency by varying application time of antisolvents

초록

The defect states and photoelectric conversion efficiency (PCE) were studied in the CH3NH3PbI3 (MAPbI3) solar cell with SnO2 by varying the application time of ethyl acetate antisolvent from 4 to 0.3 s. As the application time was decreased, the surface morphology of MAPbI3 thin films became smoother and its grain size was increased to 174 nm. In the device structure of Au/MAPbI3/SnO2/ITO/glass, when the application time was decreased to 0.6 s, the reverse saturation current density (J o) was decreased by 5.34 × 10–6 A cm−2, and the highest PCE of 15.51% was achieved. However, as the application time was further decreased to 0.3 s, J o increased up to 1.49 × 10–4 A cm−2 and the PCE was decreased. From deep level transient spectroscopy measurements, two defect states E2 and H1 were observed. Although the activation energy (E a), capture cross-section (σ n) and defect density (N t) of the E2 state showed different values from each device, real values of E a, σ n, and N t for E2 could be determined to 0.73 ± 0.04 eV, 1.15 × 10–16 cm2 and 8.16 × 1015 cm−3, respectively, by considering different J o values of the devices. E a, σ p, and N t of the H1 state only appeared in the shortest application times as equal to 0.46 ± 0.03 eV, 1.09 × 10–16 cm2 and 9.66 × 1015 cm−3, respectively.

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