Inverted organic solar cells using a solution-processed TiO2/CdSe electron transport layer to improve performance.

In the present work, cadmium selenide (CdSe) nanoparticles are deposited directly on TiO2 film to fabricate the TiO2/CdSe interlayer by a chemical bath deposition method. The inverted organic solar cells using poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl C61 butyric acid methyl ester (PCBM) bulk heterojunction as an active layer and TiO2/CdSe interlayer as an electron transport layer (ETL) are fabricated in air. A series of microstructural, photo-electronic, and electrochemical characterizations on these cells are performed. The TiO2/CdSe structure with respect to either the TiO2 layer or the CdSe layer as the ETL exhibits significantly enhanced external quantum efficiency (EQE) in the visible region. The photoluminescence (PL) measurement shows that the exciton dissociation in the TiO2/CdSe structure is more effective than that in either the TiO2 or CdSe structure. The Nyquist plots obtained from electrochemical impedance spectroscopy (EIS) implies that the charge recombination in the TiO2/CdSe structure can be suppressed with respect to that in either the CdSe or TiO2 structure. The photovoltaic performances of the cells with the TiO2/CdSe ETL are clearly improved compared with the reference cells only with the TiO2 layer or CdSe layer as the ETL. [ABSTRACT FROM AUTHOR]