Cost-Effective High-Performance Charge-Carrier-Transport-Layer-Free Perovskite Solar Cells Achieved by Suppressing Ion Migration

Abstract

Perovskite solar cells (PSCs) without charge-carrier-transport layers (CTLs) are theoretically achievable due to the ambipolar charge-carrier-transfer characteristics presenting in perovskites. However, the power conversion efficiency (PCE) of the CTL-free PSCs needs further improvement. Herein, we provide a breakthrough in the fabrication of the cost-effective high-performance holetransport-layer (HTL)-free PSC and trilayer PSC with device configurations of fluorine doped tin oxide (FTO)/SnO 2 /perovskite/carbon and FTO/perovskite/ carbon, respectively. We introduce perfluorotetradecanoic acid (PFTeDA) with a carbonyl unit and carbon fluorine bonds to suppress the ion migration and reduce the crystal defects in perovskites. The modified carbon-based HTL-free PSC shows a record PCE of 18.9%. Furthermore, the PFTeDA molecules are found existing at the grain boundaries between the perovskite crystals, resulting in enhanced environmental, thermal, and light stabilities for the resultant cost-effective highperformance CTL-free PSCs.

Fill Factor Assessment in Hole Selective Layer Free Carbon Electrode‐Based Perovskite Solar Cells with 15.5% Certified Power Conversion Efficiency

“…However, we recognize here that higher efficiencies have been reported in the literature for “non‐certified” C‐PSCs. [ 15,17–22 ] While the present work was in peer review, a highly significant study has been published, reporting on “certified” efficiency obtained through the I / V curve reaching 17.7% and an FF of 75%. [ 23 ]…”

“…However, we recognize here that higher efficiencies have been reported in the literature for "non-certified" C-PSCs. [15,[17][18][19][20][21][22] While the present work was in peer review, a highly significant study has been published, reporting on "certified" efficiency obtained through the I/V curve reaching 17.7% and an FF of 75%. [23] The PCE was not the only parameter that was found to reach record numbers for HSL-free C-PSCs, as the FF obtained from the certified measurements reached 78.8% in the reverse scan and 77.1% in the forward scan, with a very low hysteresis index of 2%.…”

Ion Migration in Organic–Inorganic Hybrid Perovskite Solar Cells: Current Understanding and Perspectives

“…applied perfluorotetradecanoic acid (PFTeDA) with a carbonyl unit and carbon fluorine bonds to suppress the ion migration in perovskites. [ 107 ] The presence of PbI 2 can be clearly seen in the control sample (Figure 8d). This was due to the ion migration under the electric field.…”

“…On the basis of the dominant role of ion migration at grain boundaries, it is crucial to suppress ion migration by passivating the defects at grain boundaries. [93][94][95][96][97][98][99][100][101][102][103][104][105][106][107][108][109][110][111][112] Liu et al proposed a strategy to passivate grain boundaries and inhibit ion migration by methimazole (MMI). [113] From the EDS results, it can be seen that the intensity of I in the initial aging device decreased from the HTL side to the ETL side, indicating that I migrated in the perovskite (Figure 9a).…”

“…Capital T letters in (d,e) are included in front of the planes and directions to denote the tetragonal (T) MAPbI 3 phase indices. Reproduced with permission [107]. Copyright 2021, American Chemical Society.…”