Perovskite solar cells are well known for being low cost, solution‐based, and efficient solar cells; however, the high price of the conventional hole‐collector electrode (Spiro‐OMeTAD/Gold) and the high price and complexity of depositing gold on large scales are major barriers against commercializing them. Herein, an effective carbon composite electrode is introduced for a low‐cost perovskite solar cell with CuIn0.75Ga0.25S2 hole transport material to solve this problem. The carbon electrode is deposited by the doctor blade method using a paste composed of flakes of graphite, carbon black, and a kind of hydrophobic polymer (polystyrene or poly‐methyl methacrylate). It is investigated how the weight ratio of carbon black to graphite and type of binder affect sheet resistance and resistivity of carbon composite layer. The effects of carbon electrode composition on the charge transport resistance at the CuIn0.75Ga0.25S2/perovskite interface are investigated using impedance spectroscopy in different light intensities of white light and light with different wavelengths of 530, 660, and 740 nm. The best efficiency of 15.9% is obtained for the champion cell (fabricated outside the glovebox), which is close to the best efficiency of the reference cell with conventional Spiro‐OMeTAD/Gold hole‐collector that is 16.3%.
Inorganic
hole-transport materials (HTMs) have been frequently
applied in perovskite solar cells (PSCs) and are a promising solution
to improve the poor stability of PSCs. In this study, we investigate
solution-processed copper indium gallium disulfide (CIGS) nanocrystals
(NCs) as a dopant-free inorganic HTM in n–i–p type PSCs.
Moreover, Cs0.05(MA0.17-FA0.83)0.95Pb(I0.83Br0.17)3 mixed-halide
perovskite with proper crystalline quality and long-time stability
was utilized as the light-absorbing layer under ambient conditions.
To optimize the cell performance and better charge extraction from
the perovskite layer, the Ga concentration in the Cu(In1–X
Ga
X
)S2 composition
was changed, and the X value was altered between
0.0 and 0.75. It was shown that the CIGS band gap enhances with increasing
Ga content; thus, with tunable band gaps and engineering of the energy
level alignment, a better collection of photogenerated holes and a
reduced electron–hole recombination rate could be achieved.
The maximum power conversion efficiency of 15.6% was obtained for
the PSC with Cu(In0.5Ga0.5)S2 hole-transport
layer composition, which is the highest efficiency reported so far
for CIGS-based dopant-free PSCs. This value is very close to the efficiency
of devices fabricated with doped spiro-OMeTAD as an organic HTM. Additionally,
the stability of nonencapsulated PSCs was studied, and CIGS-based
devices demonstrated 70% retention after 90 days of aging in the dark
and in 50% relative humidity conditions. This result is quite better
than the similar measurements for the doped spiro-OMeTAD-based devices.
Different polymers have been already introduced for passivating the interfacial defects at the interface of perovskite and the organic hole transport material, meanwhile as an environmental barrier in perovskite solar cells (PSCs). Herein, polyvinylcarbazole (PVK) compared to polymethylmethacrylate (PMMA) at the interface of the perovskite (Cs0.05(MA0.83FA0.17)0.95Pb(Br0.17I0.83)3) layer and CuInS2/carbon as a low‐cost inorganic hole‐collecting electrode are investigated. By suppressing interfacial recombination using PMMA and PVK, saturation current density (in dark current) decreases one order of magnitude from 7.9 × 10−10 to 4.0 × 10−11 mA cm−2 by adding PMMA and two orders of magnitude to 9.4 × 10−12 mA cm−2 by adding PVK. By decreasing charge‐transfer resistance (measured by impedance spectroscopy), fill factor is increased (from 0.61) to 0.62 and 0.69, respectively. The efficiency of PSC with PVK/CuInS2/carbon hole‐collecting electrode is 17.69% that is significantly higher and more reproducible than that of PMMA/CuInS2/carbon and CuInS2/carbon hole‐collecting electrodes. It seems these interfacial layers also act as a barrier against penetration of carbon black and CuInS2 nanoparticles through the perovskite holes and have the functionality of a binder layer to improve the interfacial area.
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