Nanofiber-modified Electron Transport Layer for Perovskite Solar Cells

doi:10.15541/jim20230578

Abstract

Abstract:

Tin dioxide (SnO₂) is widely used in perovskite solar cell (PSC) as an electron transport material due to its high transmittance, high electron mobility, good UV stability, and low-temperature processing. However, SnO₂ electron transport layer prepared from commercial colloidal solution still faces some challenges such as easy agglomeration, defects, and energy level mismatch, limiting its performance and stability. This study improved the quality of SnO₂ films by introducing a polymer chitin nanofiber (1,2-dibenzoyloxyphenylchitin, DC) into the SnO₂ precursor solution, and systematically studied the effect of DC on the precursor solution, film and device performance. Experimental results showed that DC additive could effectively inhibit the agglomeration of SnO₂ nanoparticles, ensuring a more homogeneous dispersion in the precursor solution. The improved SnO₂ films had smaller roughness and could be better wetted by perovskite solution, which is beneficial to closer contact with the perovskite layer. Simultaneously, the oxygen vacancy defects in the SnO₂ films were effectively passivated, and the proportion of defects was reduced to 30%, further improving the quality of the films. Based on the improved energy level matching between the SnO₂ electron transport layer and the perovskite layer, the carrier extraction and transport performance was optimized. The performance of DC-modified PSC was significantly improved, and the photoelectric conversion efficiency of the optimal device reached 19.11%. This work not only overcomes the agglomeration problem of the SnO₂ electron transport layer during the preparation process, but also provides theoretical guidance and method for improving the performance of perovskite solar cells.

Key words: tin dioxide, electron transport layer, perovskite solar cell, polymer, photoelectric conversion efficiency

CLC Number:

O649

XIAO Zichen, HE Shihao, QIU Chengyuan, DENG Pan, ZHANG Wei, DAI Weideren, GOU Yanzhuo, LI Jinhua, YOU Jun, WANG Xianbao, LIN Liangyou. Nanofiber-modified Electron Transport Layer for Perovskite Solar Cells[J]. Journal of Inorganic Materials, 2024, 39(7): 828-834.

Figures/Tables 12

Fig. S1 Molecular structure of 1,2-dibenzoyloxyphenyl chitosan(DC)

Fig. S2 PCE distribution histogram of the control, DC-10%, DC-20% and DC-50% modified PSCs

Fig. 1 (a) DLS spectra of precursors, (b) DMF contact angles, and (c, d) AFM topographical images of SnO2 and SnO2-DC films Colorful figures are available on website

Fig. S3 Top-view SEM images of pristine and DC modified SnO2 films

Fig. 2 Photoelectric properties of SnO2 and SnO2-DC films (a) Sn3d and (b) O1s XPS spectra of SnO2 and SnO2-DC films; UPS spectra of (c) SnO2 and (d) SnO2-DC films; Tauc plots of (e) SnO2 and (f) SnO2-DC films; Colorful figures are available on website

Fig. 3 Energy levels, interface transport, and carrier recombination characteristics of films (a) Energy diagram of FTO, SnO2, SnO2-DC, perovskite and spiro-OMeTAD; (b) Conductivities of SnO2 and SnO2-DC films; (c) PL and (d) TRPL spectra of SnO2 and SnO2-DC films; Colorful figures are available on website

Table 1 Fitting parameters of TRPL

ETL	A₁/%	τ₁/ns	A₂/%	τ₂/ns	τ_avg/ns
SnO₂	0.30	24.36	0.57	268.80	9.31
SnO₂-DC	0.27	22.11	0.56	273.59	8.60

Fig. S4 Top-view SEM images of the perovskite films on pristine and DC modified SnO2 films

Fig. 4 Photovoltaic performance of PSC based on SnO2 and SnO2-DC (a) Schematic structure; (b) Statistical distributions of PCE; (c) J-V curves; (d) EQE spectra; Colorful figures are available on website

Table S1 Device performance parameters extracted from Fig. 4(d)

ETL	PCE/%	FF/%	V_oc/V	J_sc/(mA·cm^-2)	PCE_max/%	PCE_min/%	PCE_mean/%
SnO₂	14.74±1.43	69.77±4.47	1.03±0.02	20.46±0.84	18.13	12.45	14.74292
SnO₂-DC	16.37±1.55	72.55±4.20	1.05±0.02	21.38±0.68	19.11	14.33	16.37923

Fig. S5 J-V curves of PSCs from both forward and reverse scans

Table S2 Photovoltaic parameters of PSCs measured under reverse or forward scan

ETL	Scan direction	PCE/%	FF/%	V_oc/V	J_sc/(mA·cm^-2)	HI
SnO₂	Reverse	17.08	74.5	1051.9	21.80	0.079
SnO₂	Forward	15.73	71.0	1036.9	21.36	0.079
SnO₂-DC	Reverse	18.31	77.1	1048.4	22.64	0.004
SnO₂-DC	Forward	18.23	75.1	1068.4	22.71	0.004

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