Semitransparent inverted polymer solar cells employing a sol-gel-derived TiO2 electron-selective layer on FTO and MoO3/Ag/MoO3 transparent electrode.

Fumin Li,Chong Chen,Chunxi Li,Liang Shen,Gentian Yue,Weifeng Zhang,Furui Tan

doi:10.1186/1556-276x-9-579

Abstract

We report a new semitransparent inverted polymer solar cell (PSC) with a structure of glass/FTO/nc-TiO2/P3HT:PCBM/MoO3/Ag/MoO3. Because high-temperature annealing which decreased the conductivity of indium tin oxide (ITO) must be handled in the process of preparation of nanocrystalline titanium oxide (nc-TiO2), we replace glass/ITO with a glass/fluorine-doped tin oxide (FTO) substrate to improve the device performance. The experimental results show that the replacing FTO substrate enhances light transmittance between 400 and 600 nm and does not change sheet resistance after annealing treatment. The dependence of device performances on resistivity, light transmittance, and thickness of the MoO3/Ag/MoO3 film was investigated. High power conversion efficiency (PCE) was achieved for FTO substrate inverted PSCs, which showed about 75% increase compared to our previously reported ITO substrate device at different thicknesses of the MoO3/Ag/MoO3 transparent electrode films illuminated from the FTO side (bottom side) and about 150% increase illuminated from the MoO3/Ag/MoO3 side (top side).

Highlights

Bulk heterojunction (BHJ) polymer solar cells (PSCs) have been extensively investigated as a new energy substitute due to their low cost, solution processing capability, and flexibility in fabricating large-area devices [1,2,3,4,5,6]
Compared to our reported indium tin oxide (ITO) substrate inverted PSCs, high power conversion efficiency (PCE) about 75% increase was achieved for the fluorine-doped tin oxide (FTO) substrate device when illuminated from the FTO side and about 150% increase done when illuminated from the MoO3/Ag/MoO3 side
Compared with our previous results [19] (the device has a structure of ITO/nc-TiO2/P3HT:PCBM/MoO3 (1 nm)/Ag (10 nm)/ MoO3 (x nm)), there is a similar variation that the PCE increases with increasing MoO3 thickness when illuminated from the FTO electrode

Summary

Introduction

Bulk heterojunction (BHJ) polymer solar cells (PSCs) have been extensively investigated as a new energy substitute due to their low cost, solution processing capability, and flexibility in fabricating large-area devices [1,2,3,4,5,6]. The power conversion efficiency (PCE) of BHJ PSCs has recently achieved 9.2% or more [7,8]. One of the possible strategies to increase its PCE is to stack two or more cells with different spectra response together as tandem solar cells [8,11]. It is important to study semitransparent solar cells on the investigation of tandem solar cells.

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