HOPV12 - Blogs

4 th Hybrid and Organic Photovoltaic Conference -Uppsala 2012 93
B47- Consistent physics-based modeling of DC and small-signal behavior of dyesensitized
solar cells under different illumination conditions
Shuai Ma a , Federica Cappelluti a , Giovanni Ghione a , Adriano Sacco b , Diego Pugliese b , Andrea
Lamberti b , Elena Tresso c
a, Department of Electronics and Telecommunications, Politecnico di Torino, Corso Duca degli Abruzzi 24, Torino, 10129, IT
b, Center for Space Human Robotics @PoliTo, Istituto Italiano di Tecnologia, Corso Trento 21, Torino, 10129, IT
c, Applied Science and Technology Department, Politecnico di Torino, Corso Duca degli Abruzzi 24, Torino, 10129, IT
The development of physics-based tools able to consistently predict the cell behavior under
different operating conditions is a key issue toward the technological development of dyesensitized
solar cells (DSSCs), since it may provide deeper understanding of the many physical
mechanisms involved in the cell operation and their interplay [1-3]. In this contribution we
investigate through experiments and device-level numerical simulations, the static and
dynamic small-signal behavior of DSSCs with different architectures and under different
illumination conditions.
The adopted model exploits a mixed-mode approach where electron transport through the
nanoporous dyed TiO2 film is described by a diffusion transport model, including non-uniform
optical generation [1-2], electron trapping mechanisms [4] and recombination with iodine
species in the electrolyte and/or oxidized dye molecules [3], while electrical loss induced by
contacts, electrolyte, and series parasitic paths are modeled by compact equivalent circuit
elements.
The cells analyzed in this study were fabricated following a standard procedure, with a layer
of dye sensitized TiO2 nanoparticles as photoanode, a counter electrode constituted by a FTOcovered
glass coated with a thermally evaporated Pt thin layer, I3-/I- redox electrolyte, and a
thermoplastic polymer as sealing material. The devices were characterized through I-V
measurements under AM1.5G solar simulator, Electrochemical Impedance Spectra (EIS) under
AM1.5G illumination and in dark condition (bias voltages from 0 to 0.8 V, frequency range 10 -1
– 10 5 Hz), and Incident Photon-to-electron Conversion Efficiency (IPCE) spectra acquired in DC
mode using a 150W Xenon halogen lamp and a dual grating Czerny Turner monochromator.
Figure 1 Comparison between measured and simulated performance. Left: IPCE for photoelectrode-side (PE) and
counter-electrode-side (CE) illumination; Center: I-V under AM1.5G sun simulator; Right: Small-signal impedance of
the TiO2 film under AM1.5G sun simulator for PE illumination at bias voltage from 0.55 to 0.8 V with 0.05 V step
(parasitic series resistance, electrolyte and counter electrode contribution have been de-embedded).
The model is applied to analyze the impact of different technological parameters (TiO2 layer
thickness, used dye, cell total thickness) on the cell operation. As an example, Fig. 1 shows a
comparison between experiments and simulations of a cell with 7 um thick TiO2 film and N719
dye. All the reported simulations (I-V, IPCE, and EIS) exploit the same set of physical
parameters, and predict the overall cell behavior consistently and with good accuracy, under
both directions of illumination. The cell shows a comparatively low IPCE with respect to the
photovoltaic performance. This has been attributed to low collection efficiency under weak
© SEFIN 2012