Abstract
Although many groups have been trying to prepare perovskite solar cells (PSCs) in ambient air, the power conversion efficiency (PCE) is still low. Besides, the effect of moisture on the formation of perovskite films is still controversial. In this paper, we studied the effect of moisture on the formation of perovskite films in detail, and found that moisture can speed up the crystallizing process of PbI2 films to form poor-quality films with large grain size and surface roughness, while, for the conversion of PbI2 to perovskite films, a small amount of moisture is not adverse, and even beneficial. On this basis, we report the successful fabrication of efficient mesoporous PSCs with PCE of 16.00% under ambient air conditions at 25% relative humidity by adding a small amount of n-butyl amine into the solution of PbI2 to enhance the quality of PbI2 films and thus to achieve high-quality perovskite films with smooth surface, large crystal grains, and high crystal quality.
Highlights
Organic-inorganic perovskite solar cells (PSCs) have become a pacemaker in the photovoltaic community with a rapid increase in the power conversion efficiency (PCE) from initial 3.8% in 2009 to a recently reported 22.7% [1–3], due to the high absorption coefficient, low exciton-binding energy, long charge carrier diffusion length, and high mobility of the organic-inorganic perovskite materials [4–12]
We report the successful fabrication of efficient mesoporous PSCs with PCE of 16.00% under ambient air conditions at 25% relative humidity (RH) by adding a small amount of n-butyl amine (BTA) into the solution of PbI2 to enhance the quality of PbI2 films and to achieve high-quality perovskite films with smooth surface, large crystal grains, and high crystal quality
Combining scanning electron microscopy (SEM) and X-ray diffraction (XRD) characterizations of PbI2 and perovskite films with and without BTA additive, it is clear that moisture can speed up the crystallizing process of PbI2 films to form poor-quality films with large grain size and surface roughness, while, for the conversion of PbI2 to perovskite films, a small amount of moisture is not adverse, and even beneficial
Summary
Organic-inorganic perovskite solar cells (PSCs) have become a pacemaker in the photovoltaic community with a rapid increase in the power conversion efficiency (PCE) from initial 3.8% in 2009 to a recently reported 22.7% [1–3], due to the high absorption coefficient, low exciton-binding energy, long charge carrier diffusion length, and high mobility of the organic-inorganic perovskite materials [4–12]. The organic-inorganic perovskite materials are very sensitive to moisture due to the hygroscopic nature of the organic components [13], so the fabrication and long-term stability of PSCs in ambient air has been considered as one of the major challenges for future large-scale application. For the first method, preheating substrates has been employed as a simple and effective manufacturing process to fabricate PSCs in ambient air. One group reported a highest PCE of 7.9% by preheating substrates at 200 °C before the one-step spin-coating of perovskite films in ambient air [20]. CsPbBr3-based inorganic PSCs have been fabricated in ambient air which exhibits the highest PCE of 7.78% [21]. Tai et al reported a type of efficient and stable perovskite solar cells prepared in ambient air by using lead (II) thiocyanate precursor instead of PbI2. The devices demonstrated average PCEs over 13%, together
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