Issue 28, 2023

Strain relaxation and phase regulation in quasi-2D perovskites for efficient solar cells

Abstract

Branched iso-butylammonium (iso-BA+) tends to form a perfectly vertical crystal orientation and thus is a good choice for spacer cations. Currently, a planar p–i–n structure with PEDOT:PSS as a hole transport layer (HTL) is commonly used for iso-BA based devices. PTAA is a better candidate for hole transport compared to PEDOT:PSS, but iso-BA based perovskite solar cells (PSCs) with a PTAA HTL are rarely reported. In this work, we find that iso-BA based perovskite films prepared on a PTAA HTL have significant tensile strain, which results in the destruction of the PTAA layer after spin-coating the PCBM solution in chlorobenzene (CB) on top of the PTAA/(iso-BA)2MAn−1PbnI3n+1 (n = 4) film arising from the CB penetrating through the perovskite layer. To address this issue, we introduce 4-fluoro-phenethylammonium (F-PEA+) as a second spacer cation (SSC), which effectively releases the tensile strain in the perovskite film, thereby preventing the CB penetration. Moreover, the introduction of the F-PEA SSC promotes the formation of large-n phases in the perovskite film, achieving uniform phase distribution. The photo-generated excitons in small-n phases can be efficiently transferred to the adjacent large-n phases, and then the free carriers are transported in an interpenetrating charge transport network constructed by large-n phases, which greatly improves the exciton dissociation and carrier transport in the PSCs. By introducing the F-PEA SSC, we obtain a remarkable PCE of 17.17%, the highest efficiency so far for iso-BA based PSCs. Due to the release of tensile strain and optimization of phase distribution, the stability of the devices is also dramatically improved after introducing the F-PEA SSC.

Graphical abstract: Strain relaxation and phase regulation in quasi-2D perovskites for efficient solar cells

Supplementary files

Article information

Article type
Paper
Submitted
31 Mar 2023
Accepted
09 Jun 2023
First published
12 Jun 2023

J. Mater. Chem. A, 2023,11, 15301-15310

Strain relaxation and phase regulation in quasi-2D perovskites for efficient solar cells

H. Zhang, Z. Wang, H. Wang, X. Yao, F. Wang, S. Wang, S. Bai, J. Huang, X. Luo, S. Wu and X. Liu, J. Mater. Chem. A, 2023, 11, 15301 DOI: 10.1039/D3TA01935G

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