Interface Optimization And Carrier Dynamics Of Organic Solar Cells

In recent years,mankind's demand for energy has been increasing,and solar energy is favored as a clean and renewable new energy source.Based on the photoelectric effect,photovoltaic technology has become one of the means to efficiently use solar energy due to its low energy consumption,sustainability and environmental friendliness.As a new force in the field of photovoltaic power generation,organic solar cells have the characteristics of low cost,light weight,roll-to-roll processing,and flexibility and bendability.With the efforts of scientists,by synthesizing new optoelectronic organic materials and optimizing the device structure,the power conversion efficiency of single-junction bulk heterojunction organic solar cells has exceeded 18%,but there are still many problems to be solved urgently to achieve large-scale commercial applications.One of the problems is the low carrier transport efficiency caused by the mismatch in energy level and other physical characteristics of the interface between the electrode and the active layer.In this paper,the interlayer is used to optimize the electrode-active layer interface of the organic solar cell to improve the performance of the device,and the effects of the electrode interlayer on the carrier transport characteristics of the device are studied through various research methods.First,we used the new conjugated polymer interface materials PBSON-P and PBSON-FEO as the cathode interlayer to prepare organic solar cells with a conventional structure and an inverted structure.Through transient photoelectric technology and voltage-current light intensity dependence on the reasrch of the reasons for the improvement of device performance under different structures.The results show that the PBSON-P interlayer and the PBSON-FEO interlayer improve the device performance by improving lifetime and extraction efficiency of free carrier,effectively suppressing monomolecular and bimolecular recombination at the same time in the device.Secondly,based on the PTB7-Th:PC₇₁BM system,we prepared the Tm Py PB cathode interlayer by using methanol solvent.The optimal power conversion efficiency of this interface modified device reached 8.57%,which was similar to the performance of the PFN-Br interface modified device.The transient photoelectric research and the voltage-current light intensity dependence research show that the interface modified device can effectively improve the carrier lifetime and suppress recombination.At the same time,the performance of the Tm Py PB cathode interface modification device prepared by methanol solvent is better than that of the methanol modification device,indicating that the improvement of the interface modification device performance is less affected by the methanol solvent.Finally,Zn O:Tm Py PB composite interlayer was prepared by doping Zn O wih Tm Py PB which would be used in the inverted structure device.By adjusting the doping concentration,we found that when the Tm Py PB concentration is 4 mg/m L,the short-circuit current density and the fill factor of the device are better than the Zn O interface modified device performance.The analysis of morphology and light intensity dependence on Voc and Jsc show that it is mainly due to the effective suppression of carrier recombination in the device and the improvement of the efficiency of electrode extraction of free charge,resulting in the enhancement of device performance.We also found that when the doping concentration exceeds the optimal value,the excess material of Tm Py PB would aggregated at the interface between Zn O interlayer and the active layer and becomes a new carrier recombination center,resulting in the intensification of monomolecular recombination in the device,reducing carrier transport and Extract performance,leading to the degradation of device performance.