Green Processing And Stability Study Based On Organic And Perovskite Solar Cells

The development of human society still relies heavily on the development and utilization of traditional fossil energy sources,but as the population increases and the reserves of fossil energy sources gradually decrease,the extraction process of fossil energy sources is extremely damaging to the natural environment and seriously affects the sustainable development strategy of human beings.In order to solve the energy crisis,people began to vigorously develop renewable and clean energy,of which solar energy as a green energy has received widespread attention.The solar cell is a device that can directly convert solar energy into electricity,the development of silicon solar cells and Ga As thin film solar cells have been successfully commercialized,but its preparation process is complex,the cost is high,and the application scenario is limited.At present,organic polymer solar cells and perovskite solar cells of the third-generation solar cells are simple to prepare,low-cost,and can be prepared into flexible devices,which have become a research hotspot for scholars at home and abroad,but are still in the laboratory development stage due to the toxicity of processing solvents and device stability.To address this issue,this thesis proposes an effective method to improve the green solvent processing of organic solar cells and device stability of perovskite solar cells through the improvement of the preparation process,and the specific research is as follows.In the first part of the work,the traditional halogenated solvent preparation process for organic polymer solar cells was improved by replacing the traditional halogenated solvent treatment with a non-halogenated solvent system for green processing and achieving equally efficient devices.Ultimately,devices based on the PBDTT-DTff BT:PC₇₁BM active layer system treated with a toluene/diphenyl ether（DPE）solvent mixture achieved an energy conversion efficiency of 9.26%,which is comparable to the performance of devices treated with a chlorobenzene/1,8-diiodooctane（DIO）solvent mixture.Thin film characterization and steady-state transient photovoltaic test results indicate that the improved device performance results from the addition of DPE compared to devices treated with a single toluene solvent.The introduction of DPE effectively improves the phase separation size and the film surface morphology between the polymer donor material and the fullerene acceptor material,resulting in improved exciton separation efficiency and better interfacial contact.Meanwhile,the introduction of DPE can improve the light capture loss and enhance the light absorption existing in the toluene treated devices,and effectively improve the charge transport and extraction mechanism inside the devices,thus increasing the short-circuit current density and fill factor of the devices.Thesis also prepared devices for the current high-efficiency non-fullerenes PM6:Y6 system by solvent treatment with a toluene/DPE mixture and halogenated solvents,respectively,and that the energy conversion efficiency of the non-fullerene-based polymer solar cells prepared by non-halogenated solvent treatment reached 14.8%,which was comparable to the performance of the devices prepared by halogenated solvent treatment and showed good storage stability.This part of work provides a new idea for the green processing of organic polymer solar cells with non-halogenated solvents,which is beneficial for their commercialization and application.In the second part of the work,thesis choose FAPb I₃,which has a narrower band gap and better stability,to replace the conventional MAPb I₃ as the main material of the perovskite active layer in response to the problems of poor stability of conventional MAPb I₃ perovskite and the easy decomposition of MAI.Due to the large radius of FA ions,FA-based perovskite will have the problem of phase instability and will easily transform into hexagonal non-perovskite phase,the introduction of Cs with smaller ionic radii to partially replace FA improves the phase stability of the films and enhances the photovoltaic performance and long-term stability of the devices.Based on this,thesis introduced conjugated aromatic polymer materials（PAF-154 and PAF-155）in the perovskite precursor solution by doping and the experimental results show that the film morphology of the device doped with conjugated aromatic polymer material is further improved,the grain size is increased and the grain boundary area is reduced,which reduces the non-radiative compounding inside the device due to grain boundary defects,thus improving the carrier transport capacity and finally increasing the energy conversion efficiency of the device to 22.56%.The device can maintain the maximum efficiency in unencapsulated conditions and placed in air at room temperature and relative humidity of 40%for 4000h,still able to maintain the maximum efficiency of more than 80%.