Electrochimica Acta 46 (2001) 4243 – 4249 All-polymeric electrochromic and photoelectrochemical devices: new advances Marco-A. De Paoli *, A.F. Nogueira, D.A. Machado, Claudia Longo Laborato ´rio de Polı ´meros Condutores e Reciclagem, Instituto de Quı ´mica, Uniersidade Estadual de Campinas, C. Postal 6154, 13083 -970 Campinas, SP, Brazil Received 14 February 2001; received in revised form 3 April 2001 Abstract Flexible and solid-state electrochromic and photoelectrochemical devices were assembled using PET – ITO flexible electrodes as substrate to the electroactive layers and a polymer electrolyte based on poly(epichlorohydrin-co -ethylene oxide). Large area all-polymeric electrochromic device (20 cm 2 ) consisted of a sandwich-type cell of electrodes modified with poly(o -methoxy aniline) and poly(3,4-ethylene dioxythiophene) – poly(styrene sulfonate) films. The device exhibited a very high optical contrast (transparent to dark blue), with T % =75% at  =640 nm, however, it partially loses optical contrast after 100 redox cycles, resulting in T % =42%. The solid-state flexible photoelectro- chemical solar cell consisted of a dye-sensitized porous TiO 2 electrode and a Pt counter-electrode assembled with the polymer electrolyte containing the I 3 - /I - redox couple. This cell exhibited an open circuit potential of 0.83 V, a short-circuit photocurrent of 0.19 mA cm -2 and an efficiency of 0.09% (100 mW cm -2 ). The low efficiency for energy conversion, in comparison to cells with liquid electrolytes, was attributed to the polymer electrolyte and the reduced mobility of I 3 - in such medium as well as to the poor electronic contact between the TiO 2 particles in the porous film. © 2001 Elsevier Science Ltd. All rights reserved. Keywords: Electrochromism; Photoelectrochemistry; Devices; Polymer electrolyte www.elsevier.com/locate/electacta 1. Introduction Most of the electrochromic and photoelectrochemical devices are sandwich-type two-electrode electrochemical cells. Usually, they are assembled using a liquid elec- trolyte, which requires a perfect sealing in order to avoid leakage and evaporation of the solvent, contami- nation with impurities, etc. Also, both the elec- trochromic and the photoelectrochemically active materials are commonly deposited as film on transpar- ent glass electrodes. The use of glass electrodes brings other restrictions related to its fragility and form and shape limitations. Motivated by technological advantages that can be attained if these problems were overcome, the research for developing flexible and solid-state electrochromic [1–4] and photoelectrochemical [5–7] devices has re- cently increased. This became possible, after the large- scale production of flexible transparent electrodes, like the films of poly(ethylene terephtalate) coated with indium doped tin oxide, i.e. ITO–PET (Innovative Sputtering Technology, IST) and the advances that were attained in the field of solid electrolytes, for instance polymer electrolytes [8 – 14]. The basic require- ment to achieve a high ionic conductivity in such polymer electrolytes at room temperature is a low degree of crystallinity of the polymer and a high disso- * Corresponding author. Tel.: +55-19-239-8575; fax: +55- 19-239-3805. E-mail address: mdepaoli@iqm.unicamp.br (M.-A. De Paoli). 0013-4686/01/$ - see front matter © 2001 Elsevier Science Ltd. All rights reserved. PII: S0013-4686(01)00684-3