Inverted polymer solar cells with Zn2SnO4 nanoparticles as the electron extraction layer

In this study, we report narrow-size distribution Zn₂SnO₄ (ZSO) nanoparticles, which are produced by low-temperature solution-processed used as the electron extraction layer (EEL) in the inverted polymer solar cells (i-PSCs). Moreover, poly[(9,9-bis(3'-(N,N-dimethylamino)propyl)-2,7-fluorene)-alt-2,7-(9,9-dioctylfluorene)] (PFN) is used to modify the surface properties of ZSO thin film. By using the ZSO NPs/PFN as the EEL, the i-PSCs fabricated by poly[4,8-bis(2-ethylhexyloxyl)benzo[1,2-b:4,5-b'] dithio-phene-2,6-diyl-altethylhexyl-3-fluorothithieno [3,4-b]thiophene-2-carboxylate-4,6-diyl] (PTB7) blended with (6,6)-phenyl-C₇₁-butyric acid methylester (PC₇₁BM) bulk heterojunction (BHJ) composite, exhibits a power conversion efficiency (PCE) of 8.44%, which is nearly 10% enhancement as compared with that of 7.75% observed from the i-PSCs by PTB7:PC₇₁BM BHJ composite using the ZnO/PFN EEL. The enhanced PCE is originated from improved interfacial contact between the EEL with BHJ active layer and good energy level alignment between BHJ active layer and the EEL. Our results indicate that we provide a simple way to boost efficiency of i-PSCs.