Luminescent Efficiency in Single-layer Organic Electrophosphorescent Devices

Based on the charge injection and recombination processes and the triplet-triplet annihilation process, a model to calculate the electroluminescent(EL) efficiency is presented. The influences of the applied electric field on the injection efficiency, recombination efficiency and electroluminescent efficiency are discussed. It is found that: (1) The injection efficiency is increasing while the recombination efficiency is decreasing with the applied electric field increasing. (2) The EL efficiency is enhanced at low electric field slowly but is decreasing at high electric field with the increase of applied voltage. (3) The EL efficiency is decreasing with the increase of the host-guest molecular distance (R). So, it is concluded that the EL efficiency in single-layer organic electrophosphorescent devices is dominated by injection efficiency at lower electric field and recombination efficiency at higher electric field.

Efficiency Improvement of PV Generation System by Using Improved P ＆ O Method of MPPT

The conventional P ＆ O （perturb-and-observe） method, which is the most widely used as MPPT （maximum power point tracking） control, has the problem of low efficiency and unstable operation when solar radiation changes drastically. Aiming at this problem, this paper improves the conventional P ＆ O method to reduce the bad effect of solar radiation by shortening the sampling interval of PV module＇s output power while keeping the operating period unchanged. Experiments are conducted to study efficiency gains of improved method when solar radiation changes drastically. The result shows that, by this method, the efficiency of MPPT control can be increased 17% in average when PV module simulator is used and 20% at maximum when actual PV module is used, compared with the conventional P ＆ O method.

Large improvement of photovoltaic performance of flexible perovskite solar cells using a multifunctional phospho-ethanolamine-modified SnO_(2)layer

The non-radiative recombination loss caused by diverse defects within SnO_(2)electron transport layer(ETL),perovskite film,and their interface greatly hinders the further improvement of the performance and stability of flexible perovskite solar cells(PSCs).Therefore,it is urgent to develop an effective strategy to address these issues.Herein,a multifunctional material,phospho-ethanolamine(PE),is introduced into SnO_(2)aqueous colloids to suppress defects and prepare high-quality ETL.The results demonstrate that the incorporation of PE can significantly reduce the number of Sn dangling bonds due to the formation of new Sn–O–P bonds,which is beneficial to ameliorating the electrical properties of SnO_(2)and obtaining dense SnO_(2)film.Meanwhile,the amino group(NH_(2))of PE can interact with uncoordinated Pb^(2+)in perovskite,thereby suppressing SnO_(2)/perovskite interface defects and obtaining improved perovskite film quality.Consequently,the optimized flexible and rigid PSCs based on the SnO_(2)-PE composite ETL yield outstanding photoelectric conversion efficiency(PCE)of 18.48%and 21.61%,respectively.Moreover,flexible PSCs based on SnO_(2)-PE present excellent mechanical durability,and 90.6%of the original PCE is retained after 1000 bending cycles.