Monolithic tandem solar cells comprising electrodeposited CuInSe2 and perovskite solar cells with a nanoparticulate ZnO buffer layer

Significance Statement

High production cost and low efficiency are the key roadblocks to realizing advances in solar technology. At present, solar photovoltaics can only account for less than 2% of today’s global electricity. More so, a complex inhibition is encountered when attempts to increase the power conversion efficiency of a single-junction solar cell are made. As a result, inquest into the formation of multiple-junctions in a cell is receiving considerable attention. In recent advancements, organometal halide perovskite-based solar cells have emerged as promising top cell candidates due to their suitable electrical and optical properties. To achieve highly efficient tandem devices, the realization of a high efficiency semi-transparent perovskite solar cell is still an essential challenge. Moreover, the development of a suitable deposition process that does not deteriorate the low-cost advantage and maintains the high performance of the perovskite solar cells will be of great importance.

A team of researchers led by Doh-Kwon Lee at the Photo-electronic Hybrids Research Center, Korea Institute of Science and Technology designed semi-transparent inverted planar perovskite solar cells for monolithic tandem construction with an electrodeposited copper-indium-selenide solar cell. Their aspirations were to attempt and realize a high-efficiency monolithic thin film tandem device. In order to achieve this, they hoped to eliminate the severe degradation of the perovskite/PCBM layers during the sputtering process of the transparent conducting oxide, using a thin zinc oxide-nanoparticle introduced onto the electron-extracting PCBM layer by a simple solution process without a post-annealing step. Their research work is now published in the journal, Journal of Materials Chemistry A.

The procedure undertaken involved selecting a sputter aluminum-doped zinc oxide layer as the top transparent conducting oxide while employing a thin zinc oxide-nanoparticles layer prepared by a simple solution process as a buffer layer to protect the underlying PCBM and/or perovskite layers from possible damage during the sputter deposition of the aluminum-doped zinc oxide electrode. To demonstrate the feasibility of all-solution processed, monolithic two-terminal tandems, an electrodeposited copper-indium-selenide thin-film solar cell with a power conversion efficiency of ca. 10% was used as a bottom cell. An intrinsic zinc oxide/ aluminum-doped zinc oxide double layer was applied as a transparent recombination layer at the junction between the sub-cells by tuning its thickness. As a result, monolithically integrated, two-terminal copper-indium-selenide/perovskite tandem solar cells with a higher power conversion efficiency than the constituent single-junction devices were realized.

The research team observed that the thin zinc oxide-nanoparticles layer with an optimal thickness facilitates the electron transfer from PCBM to the silver back contact in opaque devices while also helping to protect the underlying layers from plasma-induced damage in semi-transparent devices. As a result, semi-transparent perovskite solar cell devices with an inverted architecture having a sputtered aluminum-doped zinc oxide top electrode are realized with power conversion efficiencies over 10%.

Within a semi-transparent perovskite solar cells in the p–i–n architecture, in which a solution processed zinc oxide-nanoparticles layer was introduced as an effective charge selective layer between the PCBM and transparent conducting oxide layers, has been demonstrated. It has been seen that due to the sputter-buffering ability of the zinc oxide-nanoparticles layer, an aluminum-doped zinc oxide top transparent conducting oxide layer could be deposited without causing severe plasma damage to the underlying perovskite/PCBM layers. The technique presented in their paper is important in that it allows current matching between the sub-cells, optimization of the recombination layer for good transmission of low-energy photons and low interfacial resistance and the development of a fabrication strategy that is viable for industrial use. All in all, the results obtained shed light on the possibility of all-solution-processed, highly efficient tandem solar cells.

PCBM – phenyl-C61-butyric acid methyl ester

Monolithic tandem solar cells comprising electrodeposited CuInSe2 and perovskite solar cells with a nanoparticulate ZnO buffer layer.. Renewable Energy Global Innovations

Reference

Yoon Hee Jang, Jang Mi Lee, Jung Woo Seo, Inho Kim, Doh-Kwon Lee. Monolithic tandem solar cells comprising electrodeposited CuInSe2 and perovskite solar cells with a nanoparticulate ZnO buffer layer. J. Mater. Chem. A, 2017, 5, 19439–19446

 

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