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A series of cross-linkable bipolar host materials containing carbazole (donor, D) and 1,2,4-triazole (acceptor, A) were designed and synthesized. The host materials with styryl groups can be thermally cross-linked by curing at 172–190 °C without any polymerization initiator. Excellent solvent resistance was observed for all the host materials, which is beneficial for the preparation of subsequent functional layers by solution processes. The highest occupied molecular orbital energy levels of 5.55, 5.58 and 5.54 eV are estimated for these host materials, which indicates low injection barrier from the hole transport layer. A current efficiency of 15.3 cd A–1 and an external quantum efficiency of 4.6 % were achieved for solution-processed Ir(mppy)3-based OLEDs by using the cross-linkable host material.

Artificial neural network is a powerful tool for modelling and prediction in various fields. Tobacco management specialists need simple and accurate techniques to evaluate tobacco growth and cultivation in the growth period. The objective in this study is to develop aback-propagation neural network (NN) model to accurately predict tobacco growth under various climatic and soil conditions in China. The proposed model used the field test data at 11 locations in main tobacco azeas in China. As the output of the NN, the dry weight of tobacco plants was significantly influenced by dry weigh preceding stage, time for sampling, average temperature, relative humidity, soil organic matter and available P value, so these 6 environrnent factors were taken as the NN input. In the study, an optimal NN model was developed with 6 inputs, 1 output and 19 neurons in the hidden layer. With the same test data, the proposed NN model could perform better than the conventional regression model in terms of the relative...