1
• Different variations and concentrations of CH 3 NH 3 Cl, CH 3 NH 3 Br, PbBr 2 and PbCl 2 were produced in the lab inside a glovebox. The compounds were dissolved by DMSO (dimethyl sulfoxide) and then mixed with PEO (polyethylene oxide) and PVP (Polyvinylpyrrolidone). The ratio used for the final compound was Pero 100%/ PEO 50% / PVP 4%~5%. • Afterwards, compounds were either spin-coated or drop-casted onto an ITO (indium tin oxide) /glass using a micropipette. Then, the samples were exposed to different temperatures (annealing) on a hot plate to let the perovskite crystals grow. • Finally, the samples were tested with indium gallium connecting to a Keithley source meter using 4 V to 5 V to observe if visible blue light could be emitted. A new method was adopted in this research for the production of light emitting diodes (LEDs) which emit blue light. The thin film consisted of a single layer light- emitting diode using different organometal halide perovskites (Pero). The concentration of the compounds and the temperature exposure of the films were tuned in order to obtain blue light in the devices. The more stable blue was found with the compound CH 3 NH 3 PbBr 2 Cl, 1 M with ratio 1:1.5. Single layer blue light-emitting diodes with organometal halide perovskites Zaian E. Lopez-Ramos 1 ; Xin Shan 2 ; Dr. Junqiang Li 2 ; Dr. Zhibin Yu 2 1)Padre Aníbal Reyes Belén High School, Hatillo, PR; 2)High-Performance Materials Institute, Florida State University, FL ABSTRACT EXPERIMENT RESULTS CONCLUSION Summary of results for the different compounds Compound(s) in DMSO + PEO + PVP Conditions Results MAPbBr 3 + MAPbCl 3 0.4 M Ratio: 1:1 PbBr 2 + MABr Ratio: 1:1.05 PbCl 2 + MACl Ratio: 1:1.05 Performed in the dry room. No visible light was produced. MAPbBr 3 + MAPbCl 3 0.4 M Ratio: 2:1 PbBr 2 + MABr Ratio: 1:1.05 PbCl 2 + MACl Ratio: 1:1.05 Performed in the dry room. Blue twinkling only can be seen when the light was turned off. MAPbBr 3 + MAPbCl 3 1 M Ratio: 2:1 PbBr 2 + MABr Ratio: 1:1.05 PbCl 2 + MACl Ratio: 1:1.05 Performed in the dry room. Blue twinkling can be seen but the light was turned off. The blue is more stable than previous compounds. MAPbBr 3 + MAPbCl 3 1 M Ratio: 2:1 PbBr 2 + MABr Ratio: 1:1.5 PbCl 2 + MACl Ratio: 1:1.5 Not performed in the dry room. Blue light was darker than previous. Light was turned off, yet some ambient light was present. MAPbBr 2 Cl 1 M Ratio: 1:1.5 PbBr 2 Ratio: 1 MACl Ratio: 1.5 Not performed in the dry room. Darker blue than all previous films and more stable. Blue light lasted at least 5 s. As the demand of light emitting diodes (LEDs) rises, so does new methods for their manufacture. The High Performance Materials Institute in FSU recently published results for the development of single layer green organometal halide perovskites light-emitting diodes (J. Li, et al., 2015; Bade, et al., 2015). This process is cost effective. If the results can be used to find blue radiation which have a higher stability and efficiency, it could be a breakthrough in the production of LEDs. Cross section diagram of the single layer LED developed in HPMI (Li, Bade, Shan, & Yu, 2015). References: Bade, S. G. R., Li, J., Shan, X., Ling, Y., Tian, Y., Dilbeck, T., ... & Hanson, K. (2015). Fully printed halide perovskite light-emitting diodes with silver nanowire electrodes. ACS nano, 10(2), 1795- 1801. Li, J., Bade, S. G., Shan, X., & Yu, Z. (2015). Single‐Layer Light‐ Emitting Diodes Using Organometal Halide Perovskite/Poly (ethylene oxide) Composite Thin Films. Advanced Materials, 27(35), 5196-5202. All compounds were tested in different temperatures, humidity levels, and were either drop-casted or spin- coated before applying voltage. INTRODUCTION a) On the hot plate the compounds changed from transparent to a yellow color; b) Some compounds used a lid to control the growing speed of perovskites; c) Close up view to compare the change in color between compounds (1) MAPbBr 3 + MAPbCl 3 and (2) MAPbBr 2 Cl. (MA corresponds to CH 3 NH 3) a b c a b c d e f a) 5X microscopic view of 20 μL of MAPbBr 3 + MAPbCl 3 , 1 M, 2:1, after been spin- coated at 1500 RPM for 1 minute and exposed to 100ºC for 2 minutes; b) 20X microscopic view of same compound as a, perovskite crystals can be seen between some cracks; c) 10X microscopic view of 20 μL MAPbBr 2 Cl 1 M, 1:1.5 drop- casted after exposure to 200ºC until it changed color (≈ 30s); d) 50X microscopic view of same compound as c; e) 10X microscopic view of same compound as c from a different part of the film; f) 50X microscopic view of same compound as e, the difference in form between the crystals in d and f may be due to the irregular surface of the perovskite layer in the ITO/ glass. 2 1 Even blue light emission was achieved, it was not stable enough. Some reasons for this may be the short period of time to perform this experiment and the effect of humidity and oxygen in the air. Further research is needed. Some suggestions include changing the annealing temperature to let the perovskites grow, changing the concentration of the compounds or control the atmosphere. Acknowledgments: •I want to thank all Dr. Yu Group in HPMI, like Dr. Yu, Xin (Minnie) Shan, Dr. Li, Melissa and Ganesh Bade for all their help, specially Minnie for her wonderful patience and sense of humor. Also I want to thank all the 2016 RET’s and José Sánchez for their support. •This project was funded with DMR1157490.
