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.

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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.

To push perovskite solar cells (PSCs) as efficient solution-based solar cells with remarkable photovoltaic properties into large-scale production, in addition to improving efficiency and stability, reducing the fabrication cost, and especially increasing the manufacturing speed, is crucial. In this research, we have replaced the conventional heating and sintering procedure of a bilayer (compact and mesoporous) TiO2 electron transport layer as a highly time- and energy-consuming process with a fast light-curing procedure for use in PSCs with a promising printable CuInS2/carbon hole collector. A halogen-tungsten lamp (H-lamp, 1 kW) and a mercury lamp (M-lamp, 400 W) are utilized as low-cost available sources. Results show that sintering occurs effectively in the case of light-curing using the H-lamp for 5 min as a replacement of conventional heating in the furnace at 500 °C. In the case of light-curing using the M-lamp for 20 min or heating in the furnace at 400 °C, sintering does not occur effectively and the mesoporous TiO2 layer acts as a scaffold for the perovskite layer. The effective sintering does not affect efficiency (that is 16.1 to 16.4% in the reverse scan for all the optimized samples); however, it affects hysteresis as a result of preventing charge accumulation at the interface.

Perovskite photovoltaics have the potential to significantly lower the cost of producing solar energy. However, this depends on the ability of the perovskite thin film and other layers in the solar cell to be deposited using large-scale techniques such as slot-die coating without sacrificing efficiency. In perovskite solar cells (PSCs), Spiro-OMeTAD, a small molecule-based organic semiconductor, is commonly used as the benchmark hole transport material (HTL). Despite its effective performance, the multi-step synthesis of Spiro-OMeTAD is complex and expensive, making large-scale printing difficult. Copper indium disulfide (CIS) was chosen in this study as an alternative inorganic HTL for perovskite solar cells due to its ease of fabrication, cost-effectiveness, and improvements to the economic feasibility of cell production. In this study, all layers of perovskite solar cell were printed and compared to a spin-coating-based device. Various parameters affecting the layer quality and thickness were then analyzed, including substrate temperature, print head temperature, printing speed, meniscus height, shim thickness, and ink injection flow rate. The small print area achieved spin-coating quality, which bodes well for large-scale printing. The printed cell efficiencies were comparable to the reference cell, having a 9.9% and 11.36% efficiency, respectively.

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