Conjugated Polymer‐Based Plastic Solar Cells

Abstract

A tremendous research effort was devoted to the development of photovoltaic cells during the late seventies and early eighties. During this time interest was also devoted to the development of organic semiconductors, because they offer the advantages of low cost and facile processing. Organic materials for use in photovoltaic devices require a good chemical stability and large optical absorption in the visible range. For this purpose the first studied compounds were merocyanines [1] and phthalocyanines [2], which can readily be deposited as a thin film on various even flexible substrates by vacuum evaporation. Power conversion efficiencies of such devices are about 1% for small size photovoltaic elements.It is indeed intriguing and economically advantageous to think of large area photovoltaic elements based on thin plastic films, cut from rolls and deployed on permanent structures and surfaces. In order to fulfil these low cost and large area requirements, cheap production technologies for large scale coating must be used together with low cost material. Polymer photovoltaic cells hold the potential for such low cost cells. The flexibility of chemical tailoring of desired properties, as well as the cheap technology already well developed for all kinds of plastic thin film applications, meet exactly the above mentioned demands for cheap photovoltaic device production. The mechanical flexibility of plastic materials is useful for all photovoltaic applications onto curved surfaces for indoor as well as outdoor applications.Efficiencies of the first polymeric solar cells, based on hole conducting conjugated polymers (mainly polyacetylene) were rather discouraging [3]. However, the breakthrough to higher efficiencies was achieved by switching to different classes of electron-donor type-conjugated polymers (polythiophenes (PT), poly(para-phenylene vinylene)s (PPV) and their derivatives) and by mixing them with suitable electron acceptors [4]. Prototypes of photovoltaic devices based on a polymeric donor/acceptor networks showed solar energy conversion efficiencies of around 1% [5]. In particular, the photovoltaic properties and the photophysics of conjugated polymer/fullerene solid composites have been well investigated over the last few years [6].Besides the necessity for improvement in efficiency, stability is another problem for all the applications of conjugated polymers. First experiences on conjuSemiconducting Polymers: Chemistry, Physics and Engineering. Edited by G. Hadziioannou and P. F. van Hutten

Progress in polymer solar cell

“…However, the kinetics of this degradation could be significantly decreased upon addition of electron acceptor such as fullerenes and their derivates. This is usually REIVEW Figure 13 The absorption spectrums of MDMO-PPV film as a function of time under illumination of 1506 cm −1 with different protections [80] .…”

Organic semiconductors for device applications: current trends and future prospects

“…In contrast, iridium core dendrimers with carbazole in each layer [91] exhibited twofold increase in the mobility from (3-6) × 10 -5 cm 2 /Vs for generation 1 to (7.3-12) × 10 -5 cm 2 /Vs for generation 3. Conjugated polymers have been studied extensively for their applications in flexible electronics [54,59,[92][93][94][95][96][97][98][99] and optoelectronic devices [51,93,100] as reported in the published literature. Several methods were subsequently developed to take care of the polydispersion-induced disorders in such thin films.…”

“…A number of OS-based devices, especially OLEDs [2,[47][48][49], OPV solar cells [50][51][52][53][54][55][56][57][58][59], and organic field-effect transistors (OFETs) [1,[60][61][62][63][64], are fastly being developed involving conjugated organic molecules that offer special features in terms of tunable energy band-gap, redox potentials, and charge carrier transport properties, besides being easy to process. These materials and processes are certainly going to offer the lightweight, low-cost, thinfilm, large-area, and flexible electronics of tomorrow.…”

The electronic behavior of poly(3-octylthiophene) electrochemically synthesized onto Au substrate

“…In their contribution metal/P3OT/silicon devices (metal: Au, Al) were used. They found rectification ratios up to 10 6 . The values of the potential barrier heights in the present contribution also agree with values encountered by Fang et al [33].…”

“…Another important feature of polythiophene films is a large absorption coefficient in the visible range of the electromagnetic spectrum [3,4,5]. These characteristics make polythiophene and its derivatives interesting materials for solar cell applications [6]. One of the major problems in polymer devices is the small charge carrier mobility.…”