Studies Of Photoelectronic Devices Based On Organic-inorganic Hybrid Perovskite Material

Organic-inorganic hybrid perovskite materials have emerged as a new optoelectronic semiconductor material with great application prospect.It is an ideal material for building efficient and inexpensive solar cells and light-emitting devices due to its unique opto-electrical/electro-optical conversion properties.The power conversion efficiency(PCE)of perovskite solar cells(PSCs)has skyrocketed from initial 3.8%in 2009 to 25.2%in just ten years.At the same time,the performance of perovskite light-emitting diodes(Pe-LEDs)have been improved to be comparable with conventional organic light-emitting diodes(OLED).Nowdays,perovskite materials and related devices have become one of the competitive heights in the optoelectronic energy field,which has attracted great attention from the academic and industry.However,the technology is still in the preliminary stage,realizating of highly efficient and stable devices(PSCs and Pe-LEDs)are facing great challenges.The physical mechanism of improving the devices stability also have to be further studied.This thesis mainly focuses on growing of organic-inorganic hybrid perovskite thin film,controlling crystal morphology and dimension,a series of stratges on improving efficiency and stability of perovskite optoelectronic devices(including PSCs and Pe-LEDs).It will provide theoretical basis and technical guidance for the development and application of high performance optoelectronic devices based on perovskite materials.The research contents were as follows:(1)The recombination charge at interface and degradation of perovskite layer are the key scientific problems which limited PCE and stability of PSCs.So,the process optimization in anti-solvent assisted one-step method was performed.Increasing grain size was realized by controlling nucleation density via optimizing the anti-solvent dropping time.The efficiency and stability of PSCs were improved remarkably.The PCE of PSCs based on FA0.85MA0.15Pb(I0.8Br0.2)3 as active layer had reached 20.22%for optimized device.Also,the unencapsulated stability improved from 1000 to 7000 hours at room temperature.The evolution and degradation mechanism of perovskite devices are explained by variation key parameters of heterojunction devices over time.(2)Using two-dimensional(2D)perovskite material as absorption layer or interface modification layer is an effective strategy to solve the stability issue of PSCs due to the 2D perovskite has better stable performance.Based on this idea,we designed a new 2D-PVK(PVK:9-poly-vinyl carbazole)co-modification layer to combine the 2D perovskite advantages(grain boundary passivation)and the PVK which blocking interfacial charge recombination.The structure not only benefiting to carrier transmission,but also alleviate active layer fast aging effectively.The PCE of PSCs increased from 16.5%to 21.5%and hysteresis index reduced significantly.The PCE of optimized device keeped 85.4%of its initial efficiency after 800 hours of one sun illumination.(3)There are a large number of defects at interface of perovskite optoelectronic devices,which will seriously affect the photoelectric conversion performance and stability.An organic polymer passivation layer with C=O double-bond was introduced to solve the problem.The analysis results show that the defects on film surface can be changed from active to ground state after introducing double-bond PVA(PVA:poly(vinyl acetate))passivation layer.Finally,PSCs with high efficiency,stability and low hysteresis were achieved by reducing the capture carrier activity and inhibiting the ions migration at interface.The average PCE was up to 23%,keeped 99.8%of initial efficiency after dark storage for 2000 hours and hysteresis index reduced to 0.018 when PVA passivation layer introduced.(4)A near-infrared flexible Pe-LEDs based on a ternary mixed cation perovskite Cs0.05(FA0.85MA0.15)0.95Pb(I0.85Br0.15)3 were fabricated on flexible substrates.The device shows excellent mechanical bending durability.The introduction of soft interface was the root of its excellent performance as suggested by electrochemical impedance spectroscopy analysis.