Research On Carrier Transport In Non-fullerene Organic Solar Cell

Organic solar cell（OSC）have attracted great attention due to their low price,translucency and roll-to-roll printing process.With the innovation of device structure and materials,the photoelectric conversion efficiency of OSC continues to improve.The photogenerated charges（carriers）formed in the active layer of OSC play a decisive role in the photoelectric conversion efficiency of the device.In order to study the charge transfer effect in OSC,spin coating（SC）process was used to prepare bulk heterojunction（BHJ）structure OSC.By doping the interface layer,the effects of interface layer resistance and charge recombination on the charge transfer process were studied;In addition,a planar heterojunction（PHJ）OSC with vertical phase separation effect was prepared using the Spontaneous Spreading（SS）process,and the influence of the vertical morphology of the active layer on the charge transfer process was studied.The impact of two processes on OSC performance was systematically studied,and the main results are as follows:1.BHJ photovoltaic devices were fabricated by SC process,and the anode interface layer was improved.The anode interface layer（HPMO-Sn:2PACz）based on doped small molecule 2PACz showed good photovoltaic performance.Among them,HPMO-Sn obtained from the oxidation of phosphomolybdate hydrate(H₃PMo₁₂O₄₀)by stannous chloride（Sn Cl₂）has similar photoelectric properties to PEDOT:PSS,and belongs to non-metallic cluster compound,which has more advantages in cost.Based on the high efficiency PM6:Y6 active layer system,the photovoltaic performance of devices with PEDOT:PSS,HPMO-Sn and HPMO-Sn:2PACz as the anode interface layer is 16.45%,16.40%and 17.62%,respectively.The better photoluminescence and electroluminescence quantum efficiency of HPMO-Sn:2PACz indicates that the OSC based on HPMO-Sn:2PACz has lower active/interfacial layer defects and non-radiative energy loss,so that the OSC based on HPMO-Sn:2PACz has higher open-circuit voltage.Electrochemical impedance spectroscopy and conductivity measurements indicate that the anode interface layer with 2PACz has a lower series resistance and thus a better charge collection probability,which leads to a higher device fill factor.The photoelectric conversion efficiency obtained by HPMO-Sn:2PACz devices with anode interface layer is higher than that obtained by HPMO-Sn or PEDOT:PSS devices,which is one of the highest values reported for PM6:Y6 systems.2.PHJ photovoltaic devices were fabricated by SS process.The photoelectric conversion efficiency of PHJ devices with vertical phase separation morphology is obviously higher than that of BHJ devices.SS process avoids the washing effect of the upper layer solution on the lower layer film in the spinning coating process,and the PHJ structure device treated with non-orthogonal solvent can be prepared.Firstly,BHJ,PHJ lower layer and PHJ double-layer active layer were prepared by SS process.Through atomic force microscope and transmission electron microscope analysis,the BHJ structure has a relatively uniform active layer morphology with appropriate phase separation.The obvious fiber aggregation behavior of the donor was observed in the lower active layer of PHJ,and the obvious receptor aggregation behavior was observed in the complete PHJ structure.Significant receptor aggregation was observed in intact PHJ structures.The results show that compared with BHJ structure,PHJ device has obvious vertical direction selective aggregation behavior to the receptor.The measurements of photocurrent,photovoltage and space limited charge show that the PHJ structure has lower molecular recombination behavior and more suitable mobility.The photoelectric conversion efficiency of photovoltaic devices based on PHJ structure（12.00%）is significantly higher than that of BHJ devices made by the same method（10.84%）.