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Teng Ma1 Daisuke Tadaki1 Michio Niwano2 Ayumi Hirano-Iwata1

1, Tohoku University, Sendai, , Japan
2, Tohoku Fukushi University, Sendai, , Japan

Perovskite solar cells (PSCs) have been attracting much attention due to their high performance and low fabrication cost. Recently, the power conversion efficiency (PCE) of the PSCs has surpassed other thin film technologies and reached 22.7%.[1] In most of the reports on PSCs, a sandwiched p-i-n structure was adopted to fabricate the PSCs. Owing to the advances in film formation technique and interfacial modification, the internal quantum efficiency of the sandwich PSCs has been approaching 100%. In order to further improve the performance of the PSCs, we need to fundamentally change the structure of the PSCs.
The integrated-back-contacted (IBC) structure has been adopted in the single crystal silicon solar cells and achieved the world record PCE due to the lower light loss compared to the sandwich structure.[2] If we can fabricate PSCs in the IBC structure, it is possible to further improve the PCE. In order to demonstrate whether and to what extent the IBC structure improves the PCE of the PSCs, we used a numerical simulation method to form the IBC-PSCs, and investigated the effects of the structure parameters (contact width, gap), defects (bulk, interface), and electrical parameters (lifetime, mobility) on the performance of the IBC-PSCs. The results clearly indicate that the PCE (22%) of IBC-PSCs is 10% higher than that (20%) of the sandwich PSCs when the dimension of the contacts is relatively small (based on CH3NH3PbI3 material).[3] The results in this work unveil a new approach to further boost the performance of PSCs, and provide valuable guidelines for the design and the fabrication of IBC-PSCs.

[1] Best Research-Cell Efficiencies, www.nrel.gov/pv/assets/images/efficiency-chart.png. Accessed on Oct. 31, 2017.
[2] K. Yoshikawa et al., Nature Energy 2017, 2, 17032.
[3] T. Ma et al., submitted.

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