High quality microcrystalline tetragonal p-Cu2SnS3 (CTS) films are prepared by spin-coating a single precursor of metal salts and thiourea on to 5 × 5 cm2 Mo substrates. The best of the solar cells completed on these films with a substrate configuration: glass/Mo/CTS/CdS/i-ZnO/Al:ZnO/Ni–Al and a total area of 0.5 cm2 displays an open-circuit voltage of 206 mV, a fill factor of 34.5%, a short circuit current density of 27.6 mA cm−2 and a power conversion efficiency of 1.9% under simulated AM1.5 illumination. This the best performance reported for such solar architectures obtained by solution processing, with dispersion below 20% for 24 devices.
For the first time, the key factors limiting CTS device efficiency are quantitatively established based on temperature dependent current–voltage curves and impedance spectroscopy, namely: (i) carrier recombination at the CTS/CdS interface, (ii) MoS2 non-ohmic back contact, formed due to sulfurization of the top Mo layer, with a barrier height of up to 216 ± 14 meV and (iii) the presence of two trap levels with activation energies 41 ± 0.4 meV and 206 ± 7 meV. The shallower trap is linked Cu vacancies, while the deeper trap is associated with Sn in Cu antisite defects based on DFT supercell calculations.
Tiwari, D., Koehler, T., Klenk, R. and Fermin, D.J., 2017. Solution Processed Single-Phase Cu2SnS3 films: Structure and Photovoltaic Performance. Sustainable Energy & Fuels.
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