Highly Efficient and Stable Inverted Polymer Solar Cells Integrated with a Cross-Linked Fullerene Material as an Interlayer

Abstract

A novel PCBM-based n-type material, [6,6]-phenyl-C(61)-butyric styryl dendron ester (PCBSD), functionalized with a dendron containing two styryl groups as thermal cross-linkers, has been rationally designed and easily synthesized. In situ cross-linking of PCBSD was carried out by heating at a low temperature of 160 degrees C for 30 min to generate a robust, adhesive, and solvent-resistant thin film. This cross-linked network enables a sequential active layer to be successfully deposited on top of this interlayer to overcome the problem of interfacial erosion and realize a multilayer inverted device by all-solution processing. An inverted solar cell device based on an ITO/ZnO/C-PCBSD/P3HT:PCBM/PEDOT:PSS/Ag configuration not only achieves enhanced device characteristics, with an impressive PCE of 4.4%, but also exhibits an exceptional device lifetime without encapsulation; it greatly outperforms a reference device (PCE = 3.5%) based on an ITO/ZnO/P3HT:PCBM/PEDOT:PSS/Ag configuration without the interlayer. This C-PCBSD interlayer exerts multiple positive effects on both P3HT/C-PCBSD and PCBM/C-PCBSD localized heterojunctions at the interface of the active layer, including improved exciton dissociation efficiency, reduced charge recombination, decreased interface contact resistance, and induction of vertical phase separation to reduce the bulk resistance of the active layer as well as passivation of the local shunts at the ZnO interface. Moreover, this promising approach can be applied to another inverted solar cell, ITO/ZnO/C-PCBSD/PCPDTBT:PC(71)BM/PEDOT:PSS/Ag, using PCPDTBT as the p-type low-band-gap conjugated polymer to achieve an improved PCE of 3.4%. Incorporation of this cross-linked C(60) interlayer could become a standard procedure in the fabrication of highly efficient and stable multilayer inverted solar cells.

Block copolymer strategies for solar cell technology

“…82 To rectify one of the problems with PCBM (namely its tendency to undergo excessive crystallization), research has effectively demonstrated the use of cross-linking groups. 83,84 Of similar interest are polymers carrying pendent fullerenes, 85 although they tend to suffer from aggregative effects of C 60 rather than self-assembly, 86 or linear main-chain polymers based on C 60 as a monomer, which seem to have displayed morphologies more appropriate to charge collection and transfer. 87 Further work on other acceptors such as perylene, notably perylene tetracarboxydiimide (PDI), 88,89 the poly(benzimidazobenzophenanthroline) ladder (BBL), 90 and units based on 9,9'-bifluorenylidene, 91 conversely, have shown that fullerene may not be necessary.…”

Progress in Organic Photovoltaic Fibers Research

“…The fiber-based photovoltaic cell, which was a solar collector that utilized internal reflector to confine light into an organic absorber, collected nearly 80% of the incoming photons as current, at ~3 kOhms.cm (Zhou et al, 2009). Li et al (2010) developed a mathematical model that was also supported by experimental results, for light transmission, absorption and loss in fiber-based organic solar cells using ray tracing and optical path iteration. A patent was developed about photovoltaic devices having fiber structure and their applications (Curran et al, 2009).…”

“…vanadium oxide and cesium carbonate), which are used as buffer layer of inverted polymer solar cells (Li et al, 1997). However, there is still a trade-off between stability and photovoltaic performance in inverted solar cells (Hsieh et al, 2010). Organic solar cells have many advantages such as potential to be semi-transparent, manufacture on both large or small areas compatible with mass production and low-cost, production possibility with continuous coating and printing processes on lightweight and flexible substrates (for example textiles), ecological and low-temperature production possibilities (Dennler et al, 2006a;Dennler & Sariciftci, 2005).…”

Flexible inverted polymer solar cells on polyethylene terephthalate substrate containing zinc oxide electron-collection-layer prepared by novel sol–gel method and low-temperature treatments

“…The organic active layer of polymer solar cells typically consists of a p-conjugated polymer donor and a fullerene derivative acceptor, and the power conversion efficiency (PCE) of polymer solar cells has recently achieved 6-8%. This has been driven by the development of new p-conjugated polymers [5][6][7][8] and fullerene derivatives [9,10]. In addition to increasing their efficiency, studies into their commercial viability (e.g.…”