The hole transport layer with ammonia-modified to improve luminescence efficiency of all-inorganic perovskite light-emitting diodes

Abstract

Recently, all-inorganic perovskite CsPbBr 3 has been shown to be promising for light-emitting diode applications because of its higher thermal stability and photoluminescence quantum efficiency. However, the performance of all-inorganic perovskite applied to PeLED devices still needs to be further improved. In this paper, a strategy to modify the PEDOT:PSS transport layer with ammonia was successfully developed, and an all-inorganic perovskite light-emitting diode with a ITO/PEDOT:PSS/CsPbBr 3 /TPBi/LiF/Al structure was fabricated. It is shown that the ammonia-modified PEDOT:PSS not only improved the interfacial energy barrier between the PEDOT:PSS and CsPbBr 3 layer which effectively improved the charge injection balance rate and then decreased the turn-on voltage of the proposed devices from 2.6 V to 2.3 V. In addition, the maximum luminance of the devices was increased by 5 times (2540 Cd/m 2 to 14025Cd/m 2 ), and both the current efficiency and external quantum efficiency (EQE) were enhanced 2.6 fold (1.61Cd/A to 4.17Cd/A and 0.45%–1.16% respectively). The mechanism was investigated and was found to be due to the enhancement of the peak ratio of the intensity (I(100)/I(110)) of the CsPbBr 3 layer, which effectively improved the band edge radiative recombination. The PEDOT:PSS transport layer with ammonia not only lowered the interfacial energy barrier but also improved the morphology and changed the crystallization of the CsPbBr 3 layer. As a result, after the ammonia treatment, the performance of CsPbBr 3 LED turn on voltage would be decreased from 2.6 V to 2.3 V and then the luminance would be enhanced from 2540 Cd/m 2 to 14025Cd/m 2 and both current efficiency and EQE could be improved from 1.61 Cd/A to 4.17 Cd/A and 0.45%–1.16% respectively. • The PEDOT:PSS with ammonia modified can improve the carriers injection due to the increase of HOMO level and make turn on voltage decreased from 2.6 V to 2.3 V. • The PEDOT:PSS with ammonia modified can make the I((100)/I(110) of CsPbBr 3 film to higher and enhance the recombination of carriers to improve the luminescence of the PeLED. • The PeLED performance(CE, EQE) is affected by the HOMO level and the I((100)/I(110) ratio of CsPbBr 3 film and especially deep affected by the latter. • The Luminance of device can be inproved from 2540 Cd/m 2 to 14025 Cd/m 2 and Current efficiency and EQE can be inproved from 1.61 Cd/A and 0.45% to 4.17 Cd/A and 1.16%.