The luminous efficiency of organic light-emitting devices depends on the recombination probability of electrons injected at the cathode and holes at the anode. A theoretical model to calculate the distribution of curr...The luminous efficiency of organic light-emitting devices depends on the recombination probability of electrons injected at the cathode and holes at the anode. A theoretical model to calculate the distribution of current densities and the recombination rate in organic single layer devices is presented taking into account the charge injection process at each electrode, charge transport and recombination in organic layer. The calculated results indicate that efficient single-layer devices are possible by adjusting the barrier heights at two electrodes and the carrier mobilities. Lowering the barrier heights can improve the electroluminescent(EL) efficiency pronouncedly in many cases, and efficient devices are still possible using an ohmic contact to inject the low mobility carrier, and a contact limited contact to inject the high mobility carrier. All in all, high EL efficiency needs to consider sufficient recombination, enough injected carriers and well transport.展开更多
Based on a full device model adopting three-dimensional Pauli master equation approach, the charge carrier loss process due to poor extraction channels between electrode and active layer in polymer bulk heterojunction...Based on a full device model adopting three-dimensional Pauli master equation approach, the charge carrier loss process due to poor extraction channels between electrode and active layer in polymer bulk heterojunction(BHJ) solar cells was studied. The influence of barrier height on device performance was simulated to reveal the importance of electrode improvement. It was found that relatively large extraction barrier height(over 0.40 eV) can lead to the significant diminishing of the overall charge collection efficiency, since bimolecular recombination rate would increase to a high level due to enhanced space charge accumulation effect near electrodes. In contrast, the percentage of charge carrier annihilated due to geminate recombination did not change significantly with barrier height variation. Our simulation results may provide the basis for a more accurate model and potential direction of polymer BHJ solar cells improvement.展开更多
基金Excellent Youth Foundation of Hunan Province(03JJY1008) Science Foundation for Post-doctorate of China(2004035083) Science Foundation of Central South University( 0601059)
文摘The luminous efficiency of organic light-emitting devices depends on the recombination probability of electrons injected at the cathode and holes at the anode. A theoretical model to calculate the distribution of current densities and the recombination rate in organic single layer devices is presented taking into account the charge injection process at each electrode, charge transport and recombination in organic layer. The calculated results indicate that efficient single-layer devices are possible by adjusting the barrier heights at two electrodes and the carrier mobilities. Lowering the barrier heights can improve the electroluminescent(EL) efficiency pronouncedly in many cases, and efficient devices are still possible using an ohmic contact to inject the low mobility carrier, and a contact limited contact to inject the high mobility carrier. All in all, high EL efficiency needs to consider sufficient recombination, enough injected carriers and well transport.
基金Supported by the National Natural Science Foundation of China(Nos.21174049, 91333103) and the Open Project of State Key Laboratory of Supramolecular Structure and Materials, China(No.201329).
文摘Based on a full device model adopting three-dimensional Pauli master equation approach, the charge carrier loss process due to poor extraction channels between electrode and active layer in polymer bulk heterojunction(BHJ) solar cells was studied. The influence of barrier height on device performance was simulated to reveal the importance of electrode improvement. It was found that relatively large extraction barrier height(over 0.40 eV) can lead to the significant diminishing of the overall charge collection efficiency, since bimolecular recombination rate would increase to a high level due to enhanced space charge accumulation effect near electrodes. In contrast, the percentage of charge carrier annihilated due to geminate recombination did not change significantly with barrier height variation. Our simulation results may provide the basis for a more accurate model and potential direction of polymer BHJ solar cells improvement.