Enhanced efficiency of inverted polymer solar cells by using solution-processed TiOx/CsOx cathode buffer layer.

Xiaodong Zhou,Yunli Zhang,Ziqiang Zhu,Xianke Sun,Xi Fan

doi:10.1186/s11671-015-0754-1

Xiaodong Zhou, Yunli Zhang + Show 3 more

Open Access

https://doi.org/10.1186/s11671-015-0754-1

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Abstract

In this work, a double-buffer film of TiOx coated with CsOx (TiOx/CsOx) was solution prepared to be applied in poly(3-hexylthiophene):indene-C60 bisadduct (P3HT:ICBA) and P3HT:[6,6]-phenyl-C61-butyric acid methyl ester (PCBM) inverted polymer solar cells (PSCs). Compared with TiOx films and CsOx films, the TiOx/CsOx double-buffer film exhibited a favorable energy-level alignment among TiOx, CsOx, and the electron acceptor of PCBM or ICBA a better surface morphology; and an enhanced wetting and adhesion property with a contact angle of 21.0°, leading to a higher electron mobility of 5.52 × 10−3 cm2 V−1·s−1. Moreover, the P3HT:ICBA and P3HT:PCBM photovoltaic devices with the double-buffer film showed the best power conversion efficiency up to 5.65% and 3.76%, respectively. Our results not only present that the double-buffer film is superior than the single film of TiOx and CsOx, but also imply that the solution-processed film has a potential to be generally used in roll-to-roll processed organic photovoltaic devices.

Highlights

Polymer solar cells (PSCs) have been a hot research topic due to their advantages of low cost, light weight, and large area [1,2,3,4]
Normal polymer solar cells (PSCs) with a considerable power conversion efficiency (PCE) of 7% ~ 9% have been reported [5,6,7,8,9,10,11,12,13,14,15]. In such normal PSCs, aqueous poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) dispersion is acidic at pH 1 and corrosive to indium tin oxide substrates [16]; In addition, PSS and Al could diffuse into active layers and react with organic active layers [17]; instability of PSC devices caused by the anode buffer layer of PEDOT:PSS and the Al cathode has become a main concern for practical applications
The results indicate that the titanium oxide (TiOx)/cesium oxide (CsOx) is superior than the TiOx and the CsOx, for the better interfacial contact, and for the achievement of the higher electron mobility, and thereby leading to an enhanced device performance

Summary

Introduction

Polymer solar cells (PSCs) have been a hot research topic due to their advantages of low cost, light weight, and large area [1,2,3,4]. Normal (not inverted) PSCs with a considerable power conversion efficiency (PCE) of 7% ~ 9% have been reported [5,6,7,8,9,10,11,12,13,14,15]. For efficient PSCs, a good CBL often satisfies several criteria: high transparency, low work function (WF), and favorable energy levels matched well with those of electron acceptors. Afterwards, the films of low WFs facilitate electron collection by cathodes and restrain the charge

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