Investigation of post-thermal annealing-induced enhancement in photovoltaic performance for squaraine-based organic solar cells

doi:10.1007/s11706-020-0490-z

Front. Mater. Sci.

2020, Vol. 14

Issue (1) : 81-88 https://doi.org/10.1007/s11706-020-0490-z

RESEARCH ARTICLE

Investigation of post-thermal annealing-induced enhancement in photovoltaic performance for squaraine-based organic solar cells

Rui ZHU², Feiyang LIU¹, Zixing WANG¹, Bin WEI¹, Guo CHEN¹(

)

¹. Key Laboratory of Advanced Display and System Applications (Ministry of Education), Shanghai University, Yanchang Road 149, Shanghai 200072, China
². School of Environmental and Chemical Engineering, Jiangsu University of Science and Technology, Zhenjiang 212003, China

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Abstract

In this work, we have systematically investigated the post-thermal annealing-induced enhancement in photovoltaic performance of a 2,4-bis[4-(N, N-diisobutylamino)-2,6-dihydroxyphenyl] squaraine (DIBSQ)/C₆₀ planar heterojunction (PHJ) organic solar cells (OSCs). An increased power conversion efficiency (PCE) of 3.28% has been realized from a DIBSQ/C₆₀ device with thermal annealing at 100 °C for 4 min, which is about 33% enhancement compared with that of the as-cast device. The improvement of the device performance may be mainly ascribed to the crystallinity of the DIBSQ film with post-thermal annealing, which will change the DIBSQ donor and C₆₀ acceptor interface from PHJ to hybrid planar-mixed heterojunction. This new donor–acceptor heterojunction structure will significantly improve the charge separation and charge collection efficiency, as well as the open circuit voltage (V_oc) of the device, leading to an enhanced PCE. This work provides an effective strategy to improve the photovoltaic performance of SQ-based OSCs.

Keywords organic solar cell squaraine dye post-thermal annealing donor/acceptor interface power conversion efficiency

Corresponding Author(s): Guo CHEN

Online First Date: 02 January 2020 Issue Date: 05 March 2020

Cite this article:

Rui ZHU,Feiyang LIU,Zixing WANG, et al. Investigation of post-thermal annealing-induced enhancement in photovoltaic performance for squaraine-based organic solar cells[J]. Front. Mater. Sci., 2020, 14(1): 81-88.

URL:

https://academic.hep.com.cn/foms/EN/10.1007/s11706-020-0490-z
https://academic.hep.com.cn/foms/EN/Y2020/V14/I1/81

Fig.1 (a) The device architecture and (b) the corresponding schematic energy level diagram and the molecular structures of the DIBSQ/C₆₀ PHJ solar cells.

Fig.2 UV-vis absorption spectra of DIBSQ (9 nm) film, C₆₀ (40 nm) film and DIBSQ (9 nm)/C₆₀ (40 nm) bi-layer film.

Fig.3 (a) J–V characteristics under AM1.5G solar spectrum at 100 mW·cm⁻² illumination and (b) EQE spectra of DIBSQ/C₆₀ PHJ devices with post-thermal annealing treatment at various temperatures.

Tab.1 Device performance of DIBSQ/C₆₀ PHJ cells with post-thermal annealing at various temperatures

Fig.4 Photovoltaic characteristics of DIBSQ/C₆₀ PHJ solar cells with post-thermal annealing treatment at various temperatures under Am1.5G solar spectrum at 100 mW·cm⁻² illumination: (a) J_sc & PCE and (b) V_oc & FF versus the post-thermal annealing temperature.

Fig.5 AFM topographic and 3D images of a 9 nm-thick DIBSQ film: (a) as-cast and (b) after thermal annealing at 100 °C for 4 min.

Fig.6 XRD patterns of 9 nm-thick DIBSQ films: as-cast and after thermal annealing at various temperatures for 4 min.

Fig.7 The diagram of the DIBSQ/C₆₀ bi-layer interface in the DIBSQ/C₆₀ OSC device (a) before and (b) after post-thermal annealing treatment.

Fig.8 J_ph–V_eff characteristics measured at the AM1.5G condition (100 mW·cm⁻²) of DIBSQ/C₆₀ PHJ devices before and after post-thermal annealing treatment.

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