Novel p-Type Conductive Semiconductor Nanocrystalline Film as the Back Electrode for High-Performance Thin Film Solar Cells

Abstract

Thin film solar cells, due to the low cost, high efficiency, long-term stability, and consumer applications, have been widely applied for harvesting green energy. All of these thin film solar cells generally adopt various metal thin films as the back electrode, like Mo, Au, Ni, Ag, Al, graphite, and so forth. When they contact with p-type layer, it always produces a Schottky contact with a high contact potential barrier, which greatly affects the cell performance. In this work, we report for the first time to find an appropriate p-type conductive semiconductor film, digenite Cu9S5 nanocrystalline film, as the back electrode for CdTe solar cells as the model device. Its low sheet resistance (16.6 Ω/sq) could compare to that of the commercial TCO films (6-30 Ω/sq), like FTO, ITO, and AZO. Different from the traditonal metal back electrode, it produces a successive gradient-doping region by the controllable Cu diffusion, which greatly reduces the contact potential barrier. Remarkably, it achieved a comparable power conversion efficiency (PCE, 11.3%) with the traditional metal back electrode (Cu/Au thin films, 11.4%) in CdTe cells and a higher PCE (13.8%) with the help of the Au assistant film. We believe it could also act as the back electrode for other thin film solar cells (α-Si, CuInS2, CIGSe, CZTS, etc.), for their performance improvement.

Salt‐Assisted Growth of P‐type Cu9S5 Nanoflakes for P‐N Heterojunction Photodetectors with High Responsivity

“…From the KPFM test and the reported band structure of Cu 9 S 5 , the band diagrams of Cu 9 S 5 /MoS 2 is drawn in Figure f. It can be seen that a Type‐II contact is formed between Cu 9 S 5 and MoS 2 , which facilitates the charge separation and transfer in the p‐n junction.…”

Low-cost solution-processed digenite Cu9S5 counter electrode for dye-sensitized solar cells

“…47-1748) and previous report. 19 XPS was carried out to further conrm the structure of Cu 9 S 5 lm on the FTO substrate. The peaks at binding energy energies of 931.95 and 932.85 eV in Fig.…”

“…Then, the substrates were further treated by UVO-Cleaner for 30 min. The preparation of the precursor solutions as follows: 19 an equiv. of CuCl 2 was dispersed in DMF by ultrasound to dissolve.…”

“…[9][10][11][12][13][14][15][16][17] Among the family of metal suldes, several copper sulde compounds, which showed good catalytic property, high conductivity, as well as economical fabrication, have attracted much attention in quantum dotsensitized solar cells and thin lm solar cells. 18,19 However, the use of copper sulde as a CE material in DSSCs has been rarely reported until now. Lam and co-workers reported a copper sulde-based CE fabricated from precursor decomposition method involving a high temperature (500 C) sintering process.…”

Synthesis of Nonstoichiometric Cu2ZnSnS4 from ZnS by Cation Exchange

“…The high‐temperature sulfurization of CZTS also results in sulfurization of metal oxide semiconductors such as ZnO, TiO 2 , thereby limiting in situ fabrication of highly efficient solar cells. As synthesized, CZTS is also often contaminated with impurities such as highly conductive or narrow‐band‐gap Cu x S, Sn x S, and Cu–Sn–S . These impurities trap carriers and act as recombination centers.…”