Effect of processing temperature on film properties of ZnO prepared by the aqueous method and related organic photovoltaics and LEDs

The aqueous processed ZnO ETLs enable low-temperature, simple and green-strategy fabrication for efficient OPVs and OLEDs.

Co-functionalized organic/inorganic hybrid ZnO nanorods as electron transporting layers for inverted organic solar cells

In an unprecedented attempt, we present an interesting approach of coupling solution processed ZnO planar nanorods (NRs) by an organic small molecule (SM) with a strong electron withdrawing cyano moiety and the carboxylic group as binding sites by a facile co-functionalization approach. Direct functionalization by SMs (SM-ZnO NRs) leads to higher aggregation owing to the weaker solubility of SMs in solutions of ZnO NRs dispersed in chlorobenzene (CB). A prior addition of organic 2-(2-methoxyethoxy)acetic acid (MEA) over ZnO NRs not only inhibits aggregation of SMs over ZnO NRs, but also provides enough sites for the SM to strongly couple with the ZnO NRs to yield transparent SM-MEA-ZnO NRs hybrids that exhibited excellent capability as electron transporting layers (ETLs) in inverted organic solar cells (iOSCs) of P3HT:PC60BM bulk-heterojunction (BHJ) photoactive layers. A strongly coupled SM-MEA-ZnO NR hybrid reduces the series resistance by enhancing the interfacial area and tunes the energy level alignment at the interface between the (indium-doped tin oxide, ITO) cathode and BHJ photoactive layers. A significant enhancement in power conversion efficiency (PCE) was achieved for iOSCs comprising ETLs of SM-MEA-ZnO NRs (3.64%) advancing from 0.9% for pristine ZnO NRs, while the iOSCs of aggregated SM-ZnO NRs ETL exhibited a much lower PCE of 2.6%, thus demonstrating the potential of the co-functionalization approach. The superiority of the co-functionalized SM-MEA-ZnO NRs ETL is also evident from the highest PCE of 7.38% obtained for the iOSCs comprising BHJ of PTB7-Th:PC60BM compared with extremely poor 0.05% for non-functionalized ZnO NRs.

Optimization of the zinc oxide electron transport layer in P3HT:PC61BM based organic solar cells by annealing and yttrium doping

Yttrium-doped zinc oxide was utilized as an efficient electron-transport layer in P₃HT:PC₆₁BM based solar cells.

Development of a julolidine-based interfacial modifier for efficient inverted polymer solar cells

We demonstrate the julolidine moiety is an excellent electron donating building block for developing interfacial modifiers to improve the ZnO surface properties in inverted polymer solar cells.

Effects of TiO₂ interfacial atomic layers on device performances and exciton dynamics in ZnO nanorod polymer solar cells

The performances of organic electronic and/or photonic devices rely heavily on the nature of the inorganic/organic interface. Control over such hybrid interface properties has been an important issue for optimizing the performances of polymer solar cells bearing metal-oxide conducting channels. In this work, we studied the effects of an interfacial atomic layer in an inverted polymer solar cell based on a ZnO nanorod array on the device performance as well as the dynamics of the photoexcited carriers. We adopted highly conformal TiO2 interfacial layer using plasma enhanced atomic layer deposition (PEALD) to improve the compatibility between the solution-prepared active layer and the ZnO nanorod array. The TiO2 interfacial layer facilitated exciton separation and subsequent charge transfer into the nanorod channel, and it suppressed recombination of photogenerated carriers at the interface. The presence of even 1 PEALD cycle of TiO2 coating substantially improved the short-circuit current density (Jsc), open circuit voltage (Voc), and fill factor (FF), leading to more than 2-fold enhancement in the power conversion efficiency (PCE). The dynamics of the photoexcited carriers in our devices were studied using transient absorption (TA) spectroscopy. The TA results clearly revealed that the TiO2 coating played a key role as an efficient quencher of photogenerated excitons, thereby reducing the exciton lifetime. The electrochemical impedance spectra (EIS) provided further evidence that the TiO2 atomic interfacial layer promoted the charge transfer at the interface by suppressing recombination loss.