Tetrahydrofuran as an Oxygen Donor Additive to Enhance Stability and Reproducibility of Perovskite Solar Cells Fabricated in High Relative Humidity (50%) Atmosphere

Abstract

In sequential deposition method of lead‐halide perovskite material, the PbI2 layer morphology and remnant PbI2 play an important role in enhancing the power conversion efficiency (PCE) of the perovskite solar cell. However, humidity levels affect the PbI2 and perovskite film morphology, resulting in defect sites and recombination centers on the surface and within the bulk of the material, thus impeding the overall device performance and stability. To address this, incorporation of tetrahydrofuran (THF) additive in PbI2–dimethylformamide (DMF) precursor solution is reported, to improve the quality of PbI2 thin films and to prevent the water interaction directly with PbI2 under high humidity environments. The O‐donor THF interacts with PbI2, resulting in a homogeneous, dense, and pinhole‐free layer as compared with the PbI2 layer without additive. The perovskite layer so obtained from the pinhole‐free PbI2 layer is compact, resulting in a significant reduction of defects/traps. The device is fabricated with modified perovskite in ≈50% humidity atmosphere, resulting in 15% efficiency with high reproducibility. Moreover, the THF‐modified non‐encapsulated perovskite device retains 80% PCE after exposure to 50% relative humidity for 20 days. A strategy to fabricate perovskite solar cells, with reproducible efficiency in high humidity atmosphere viable for large‐scale production, is demonstrated.

Ambient Fabrication of Organic–Inorganic Hybrid Perovskite Solar Cells

“…Reproduced with permission. [193] Copyright 2019, Wiley-VCH GmbH. Ko et al [198] used a substrate heating treatment to fabricate PSCs with a best PCE of 15.76% under 50% humidity.…”

“…e) Top‐view SEM images of PbI 2: i) with THF additive and ii) without THF and the iii,iv) corresponding perovskites films, respectively. [ 193 ] f) J – V curve of THF treated PSCs and control group. Reproduced with permission.…”

“…Similarly, tetrahydrofuran (THF) as an oxygen donor (O‐donor) additive can enhance the stability and reproducibility of PSCs in a humid atmosphere. [ 193 ] O‐donor THF was found to interact with PbI 2 which resulted in a homogeneous, dense and pinhole‐free layer of PbI 2 . The resulting perovskite layer was therefore compact and resulted in a significant reduction in defects as shown in the SEM image in Figure 13e.…”

The Progress of Additive Engineering for CH3NH3PbI3 Photo-Active Layer in the Context of Perovskite Solar Cells

“…The study demonstrated that THF and PbI 2 in DMF interact and form a complex, resulting in dense, homogenous, and pinhole-free film due to complex formation between the Pb and O donor from THF, because of the Lewis acid nature of Pb and Lewis basicity of THF. This, in turn, avoids a direct interaction of PbI 2 with water, improving T80 (T80 is the time at which PCE is degraded to 80% of initial PCE) for 20 days in the ambient environment, with 50% RH, when devices were exposed unencapsulated [113]. Similarly, the liquid additive diethyl ether was also found to influence the crystallization process, resulting in large grains, leading to improved photocurrent properties and performance [114].…”

Green solvents, materials, and lead-free semiconductors for sustainable fabrication of perovskite solar cells

“…Tetrahydrofuran (THF) is a non-halogenated, non-aromatic alternative to CB and toluene, which effectively dissolves HTMs, besides being also used as additive to form a superior absorber layer. [263][264][265] Wu et al determined that a smaller amount of spiro-OMeTAD is required when cast from THF rather than from CB. 266 The same group also synthesized new small molecules dissolved in THF with efficiencies of around 18%.…”