Fabrication and Performance of Organic Optoelectronic Devices with Alkali Metal Salts as a Cathode Interlayer†

doi:10.7503/cjcu20140662

Abstract

Abstract:

Highly efficient organic small molecular light-emitting diodes(SMOLEDs), polymer light-emitting diodes(PLEDs) and polymer solar cells(PSCs) were fabricated using alkali metal salts(LiF, NaF, CsF and Cs₂CO₃) as a cathode interlayer. In SMOLEDs and PLEDs, introducing CsF as a cathode interlayer gives rise to the highest luminous efficiency and power efficiency in the four alkali metal salts. It is apparent that effect of LiF, NaF, CsF and Cs₂CO₃ as a cathode interlayer on device performance is different and modification ability sequence of the four alkali metal salts is CsF>Cs₂CO₃>NaF>LiF. When LiF is selected as a cathode interlayer in PSCs with poly(3-hexylthiophene)(P3HT)∶phenyl-C61-butyric acid methyl ester(P $C 6 0$ BM) as an active layer, power conversion efficiency(PCE) can reach 4.12% while PCE values of PSCs with NaF, Cs₂CO₃ and CsF as a cathode interlayer are 3.72%, 3.55% and 3.2%, respectively. We further found that the alkali metals atoms which decomposed from the alkali metal salts and diffused into organic layer may influence the efficiency and current density of the SMOLEDs, PLEDs and PSCs.

Key words: Organic small molecular light-emitting diode, Polymer light-emitting diode, Polymer solar cell, Cathode interlayer, Alkali metal salt, Power coversion efficiency

CLC Number:

O644.19
O63

TrendMD:

SUN Shuheng, WU Ying, ZHOU Weilong, CHEN Youchun, LI Fenghong. Fabrication and Performance of Organic Optoelectronic Devices with Alkali Metal Salts as a Cathode Interlayer^†[J]. Chem. J. Chinese Universities, 2015, 36(2): 349.

Figures/Tables 7

Fig.1 Energy level diagrams of SMOLEDs(Devices 1—4, A), PLEDs(Devies 5—8, B) and PSCs(Devices a—d, C) AMS: LiF, NaF, CsF or Cs2CO3.

Fig.2 J-V characteristics of Devices 1(LiF, a), 2(NaF, b), 3(CsF, c) and 4(Cs2CO3, d)

Fig.3 J0.5-V characteristics of Devices Ⅰ(LiF, a), Ⅱ(NaF, b), Ⅲ(CsF, c) and Ⅳ(Cs2CO3, d)

Fig.4 LE-J(A) and PE-J(B) characteristics of Devices 1(LiF, a), 2(NaF, b), 3(CsF, c) and 4(Cs2CO3, d)

Fig.5 LE-J(A) and PE-J(B) characteristics of Devices 5(LiF, a), 6(NaF, b), 7(CsF, c) and 8(Cs2CO3, d)

Fig.6 J-V characteristics of Devices a(LiF, a), b(NaF, b), c(CsF, c) and d(Cs2CO3, d)

Table 1 Performances of the PSCs with different alkali metal salts(AMSs)

Device	AMS	PCE(%)	J/(mA·cm^-2)	V_oc/V	FF(%)	R_s/(Ω·cm²)	R_sh/(Ω·cm²)
a	LiF	4.19	10.11	0.655	63	11.10	1520
b	NaF	3.72	9.95	0.655	57	11.83	792
c	CsF	3.20	9.36	0.649	53	15.31	409
d	Cs₂CO₃	3.55	9.46	0.649	58	11.50	556

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