Combining Electron‐Accepting Phthalocyanines and Nanorod‐like CuO Electrodes for p‐Type Dye‐Sensitized Solar Cells

Abstract

Esta es la versión de autor del artículo publicado en: This is an author produced version of a paper published in: El acceso a la versión del editor puede requerir la suscripción del recurso Access to the published version may require subscription COMMUNICATION Combining novel electron-accepting phthalocyanines and nanorod-like CuO electrodes for p-type dye-sensitized solar cellsOliver Langmar, [a] Carolina R. Ganivet, [b] Annkatrin Lennert, [a] Rubén D. Costa, [a] Gema de la Torre, [b] Tomás Torres, [b] and Dirk M. Guldi [a] Abstract: In the current work, a novel route for the synthesis of two electron-accepting phthalocyanines featuring linkers with different length as sensitizers for p-type dye-sensitized solar cells are reported. Importantly, our devices -based on novel nanorod-like CuO photocathodes -feature efficiencies of 0.191%, which are to date the highest values ever reported for CuO-based DSSCs.Current developments in p-type DSSCs focuses on exploring novel electrodes and electron acceptors. [1,2] Concerning the former, the most prominent material has been nickel(II) oxide (NiO), despite drawbacks such as low transparency, electrode thickness, and low conductivity. [2] To tackle some of the aforementioned bottlenecks, the preparation of binary NiXO semiconductors, where X is cobalt, have recently evolved as a powerful approach.[3] A viable alternative is based on the long overlooked copper(II) oxide (CuO), whose films feature higher conductivity, better charge carrier mobility, and comparable valence band energy relative to NiO films. [4,5] Still, the most recent report on CuO based p-type DSSCs is dated from 2008.[6] Very likely, state-of-the-art efficiencies as low as 0.011% resulted in a moderate interest. Recent improvements in the field of CuO based p-type DSSCs are due to the use of copper delafossite (CuXO2) electrodes with X being aluminum, chromium, or gallium.[ [8] perylenediimides, [9] perylene-bithiophene-triphenylamine triads, [10] porphycenes, [11] and ruthenium complexes, [12] have been designed and probed. Notably, porphyrinoids have led to the most efficient n-type DSSCs up to date. [13,14] Key merits of porphyrins, and specially of their synthetic related phthalocyanines , (Pcs), [15,16] are their exceptional light-harvesting features and their facile functionalization with either electrondonors or electron-acceptors, underlining their potential for DSSCs. In light of the latter, tuning the physicochemical features of phthalocyanines towards new electron-accepting dyes [17,18] by means of placing electron-withdrawing substituents at their periphery, complements, in the current work, our research regarding nanorod-like CuO electrodes. ; ii) IBX, DMSO/THF; iii) H3NSO3/H2O followed by NaClO2; iv) propargyl alcohol, Pd(PPh3)2Cl2, CuI, NEt3, THF Notably, the synergy of nanorod-like CuO DSSCs and electronaccepting Pcs enables the construction of p-DSSCs with efficiencies as high as 0.103% and 0.191% with iodine-and cobalt-based electrolytes, respectively. The latter represents...

Designing Squaraines to Control Charge Injection and Recombination Processes in NiO‐based Dye‐Sensitized Solar Cells

“…These enabled probing the chargei njection and recombination processes under deviceo peration conditions (Figure6). [33][34][35] In aN yquistp lot for the p-type DSSC, two semicircles correlate with the resistance across the dye-electrode-electrolytei nterface in the lowfrequency region and with the platinum-electrolytei nterface in the high-frequency region. [35,36] The electrical circuit model that was used for the fitting of the obtained Nyquist plots and the calculation of the resistances is shown in Figure S4.…”

“…[33][34][35] In aN yquistp lot for the p-type DSSC, two semicircles correlate with the resistance across the dye-electrode-electrolytei nterface in the lowfrequency region and with the platinum-electrolytei nterface in the high-frequency region. [35,36] The electrical circuit model that was used for the fitting of the obtained Nyquist plots and the calculation of the resistances is shown in Figure S4. Under 1sun AM 1.5 and J sc conditions, the charge-transfer resistance (R CT )c learly relatest ot he charge injection, as the devicer uns under maximum photocurrent generation and, thus, recombination is at its minimum.…”

“…Under 1sun AM 1.5 and J sc conditions, the charge-transfer resistance (R CT )c learly relatest ot he charge injection, as the devicer uns under maximum photocurrent generation and, thus, recombination is at its minimum. [34,35] The R CT su nder J sc conditions are 669.2, 648.4, 879.9, and 662.7 W for O2-, O4-, CN2-, and CN4based DSSCs, respectively.…”

“…From the EIS measurements under dark and 1sun AM 1.5 conditions, the effective diffusion length (L eff )a nd the charge collection efficiency (h cc )w ered erived ( Figure S5). [33,35,37] L eff and h cc give insights into the ratio of charge injection and recombination of the investigated devices. The former is am easure of how far the injected holes travel inside the mesoporous NiO electrode prior to the recombination process, whereas the latter relatest ot he amount of injected holes that are collected at the back contact of the device.A ll devices show increasing L eff sa nd h cc su pon decreasing the appliedv oltage.…”

“…As am atter of fact, this is characteristic for p-type DSSCs. [33,35] Under V oc conditions, CN4 showst he longest L eff with 1.21 mm, which decreasest o0 .99, to 0.93, and to 0.86 mmf or O2, O4,a nd CN2, respectively.U nder the same conditions, h cc increases in the www.chemsuschem.org order of 29.3 (O4), 42.6 (O2), 44.4 (CN2), and 44.9 %( CN4). Consideringt hese parameters, the use of four anchoring groups seems to be only beneficiali ft he system is locked into a cis conformation (CN4 versus O4).…”