Performance Optimization of Ultra-long Stable Mixed Cation Perovskite Solar Cells

doi:10.15541/jim20230098

Abstract

Abstract:

Perovskite solar cells (PSCs) are developing rapidly and their power conversion efficiency (PCE) has been repeatedly refreshed, but their long-term stability still needs to be improved. At present, most of the preparation of high-efficiency PSCs is completed in the inert gas, with high cost and limited operating space, which is not conducive to its industrial application. Here, perovskite solar cells with mixed cation, displaying ultra-long stability, were successfully prepared in the air. Effects of A-site cation doping on the microstructure, optoelectronic properties and stability of the perovskite were systematically investigated. The experimental results show that FA⁺ and Cs⁺ co-doping improves the quality of perovskite films, modulates the energy level arrangement of perovskite/SnO₂, suppresses carrier complexation, and significantly improves the PCE, long-term, wet and thermal stability of the cell. The optimal PCE of Cs_0.05MA_0.35FA_0.6PbI₃ cells is 19.34%, maintaining 85% of the initial efficiency after reserving for 242 d in dark environment at (20±5) ℃ and <5% relative humidity. In contrast, the PCE of the MAPbI₃cell decreased to 30% of the initial value after reserving for 112 d under the same test conditions. FA⁺and Cs⁺ co-doping also significantly improved the thermal and moisture resistance of the cells. Cs_0.05MA_0.35FA_0.6PbI₃ PSCs remain 99% and 84% of initial PCE after aging for 96 h at (85±5) ℃ and 20%-30% relative humidity, (20±5) ℃ and 80%-90% relative humidity in the dark, respectively. In contrast, PCEs of MAPbI₃ PSCs under the same conditions remain only 70% and 56%. This study provides a reference for the preparation of highly efficient and ultra-long stable mixed cation solar cells in the air.

Key words: perovskite solar cell, mixed cation, long-term stability, full-air environment preparation

CLC Number:

TQ174

MA Tingting, WANG Zhipeng, ZHANG Mei, GUO Min. Performance Optimization of Ultra-long Stable Mixed Cation Perovskite Solar Cells[J]. Journal of Inorganic Materials, 2023, 38(12): 1387-1395.

Figures/Tables 21

Fig. 1 Flow chart for the preparation of perovskite films and device manufacturing by two-step spin coating in the air

Fig. 2 Crystal structures and morphologies of different samples (a) XRD patterns; (b) Locally magnified XRD patterns in the range of 2θ=12.8°-15°; (c, e, g) SEM images and (d, f, h) Statistical distributions of grain diameter for (c, d) MP, (e, f) MFP, and (g, h) CMFP

Fig. 3 Photovoltaic performances of PSCs Statistical diagram of (a) PCE, (b) Jsc, (c) Voc, and (d) FF; (e) J-V curves; (f) EQE spectra. Colorful figures are available on website

Table 1 Photovoltaic parameters of three types of perovskite solar cells

Sample	J_sc/(mA•cm^-2)	V_oc/V	FF	PCE/%	PCE_max/%
MP	21.32±0.99	0.95±0.03	0.74±0.02	15.11±0.86	16.31
MFP	22.94±0.98	0.99±0.04	0.76±0.03	17.18±0.61	18.87
CMFP	22.24±0.77	1.03±0.03	0.78±0.02	17.83±0.33	19.34

Fig. 4 Photoelectric properties and energy levels of three perovskite films (a) UV-Vis absorption spectra; (b) Tauc plots; (c) PL and (d) TRPL spectra excited from the perovskite layer;(e) Energy level schematics of three samples

Fig. 5 Interface transmission and carrier recombination characteristics of PSCs (a) PL and (b) TRPL spectra excited from FTO layer; (c) Dark-state EIS profiles of the device at 0.8 Vbias with inset showing an equivalent circuit diagram

Fig. 6 Long-term stabilities of three perovskite solar cells at (20±5) ℃, relative humidity <5% in the dark

Fig. 7 Dark state EIS profiles of (a) MP, (b) MFP, (c) CMFP PSCs before and after aging at (20±5) ℃ and relative humidity<5%

Fig. 8 Thermal stability of three PSCs at (85±5) ℃ and relative humidity 20%-30% in the dark

Fig. 9 Wet stability of three PSCs at (20±5) ℃ and relative humidity 80%-90% in the dark

Fig. S1 UPS profiles of three perovskite films (a) UPS full spectra; UPS spectra corresponding to the secondary electron cutoff region for (b) MP, (c) MFP, (d) CMFP;(e) UPS valence band spectra; UPS spectra of the valence band top region with respect to the Femi level for (f) MP, (g) MFP, (h) CMFP

Fig. S2 XRD patterns of three perovskite thin films over time at 85 ℃, 20%-30% RH (a) MP; (b) MFP; (c) CMFP

Fig. S3 XRD patterns of three perovskite thin films over time at (20±5) ℃, 80%-90% RH (a) MP; (b) MFP; (c) CMFP

Table S1 Performance parameters of three best performing PSCs (Fig. 3 (e) and Fig. S1)

Sample	J_sc/(mA•cm^-2)	V_oc/V	FF	PCE_max/%	Intergrated current density/(mA•cm^-2)
MP	22.87	0.97	0.74	16.34	21.87
MFP	23.48	1.05	0.76	18.66	22.71
CMFP	23.30	1.06	0.78	19.34	22.37

Table S2 Fitting results of transient spectra (Fig. 4(d)) excited from the perovskite side

Sample	τ₁/ns	τ₂/ns	B₁	B₂	τ_mean/ns
MP	33.64	96.21	0.45	0.55	68.05
MFP	31.70	81.41	0.68	0.32	47.61
CMFP	26.51	77.12	0.22	0.78	65.99

Table S3 EVB and ECB of three perovskite films calculated from UPS profiles (Fig. S1)

Sample	Ф/eV	$E_{\text{VB}}^{\text{F}}$/eV	E_VB/eV	E_g/eV	E_CB/eV
MP	3.74	1.59	-5.33	1.61	-3.72
MFP	4.02	1.49	-5.51	1.55	-3.96
CMFP	3.93	1.47	-5.40	1.55	-3.85

Table S4 Fitting results of transient spectra (Fig. 5(b)) excited from the FTO side

Sample	${{\tau }_{1}}^{\prime }$/ns	${{\tau }_{2}}^{\prime }$/ns	${{B}_{1}}^{\prime }$	${{B}_{2}}^{\prime }$
MP	75.22	422.18	0.47	0.53
MFP	35.4	21.42	0.38	0.62
CMFP	8.21	34.52	0.76	0.24

Table S5 Fitting results of EIS (Fig. 7) data

Long-term stability		R_s/(Ω·cm²)	R_rec/(Ω·cm²)	R_nrec
Before testing	MP	32.40	4932	—
	MFP	27.18	7261	—
	CMFP	21.84	10890	—
After testing	MP	47.99	1462	0.30
	MFP	39.88	5430	0.75
	CMFP	34.16	9173	0.84

Table S6 Relative J-V values of three PSCs after long-term stability testing

Sample	FF_n	V_noc	J_nsc	PCE_n
MP	0.54	0.85	0.63	0.30
MFP	0.90	0.94	0.92	0.81
CMFP	0.88	0.96	0.90	0.85

Table S7 Relative J-V values of three PSCs after thermal stability testing

Sample	FF_n	V_noc	J_nsc	PCE_n
MP	0.81	0.89	0.87	0.70
MFP	0.94	0.94	0.92	0.93
CMFP	0.95	0.96	0.95	0.99

Table S8 Relative J-V values of three PSCs after wet stability testing

Sample	FF_n	V_noc	J_nsc	PCE_n
MP	0.72	0.86	0.88	0.56
MFP	0.89	0.92	0.90	0.78
CMFP	0.91	0.96	0.92	0.84

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