Abstract
A solvent-assisted methodology has been developed to synthesize CH3NH3PbI3 perovskite absorber layers. It involved the use of a mixed solvent of CH3NH3I, PbI2, γ-butyrolactone, and dimethyl sulfoxide (DMSO) followed by the addition of chlorobenzene (CB). The method produced ultra-flat and dense perovskite capping layers atop mesoporous TiO2 films, enabling a remarkable improvement in the performance of free hole transport material (HTM) carbon electrode-based perovskite solar cells (PSCs). Toluene (TO) was also studied as an additional solvent for comparison. At the annealing temperature of 100 °C, the fabricated HTM-free PSCs based on drop-casting CB demonstrated power conversion efficiency (PCE) of 9.73 %, which is 36 and 71 % higher than those fabricated from the perovskite films using TO or without adding an extra solvent, respectively. The interaction between the PbI2–DMSO–CH3NH3I intermediate phase and the additional solvent was discussed. Furthermore, the influence of the annealing temperature on the absorber film formation, morphology, and crystalline structure was investigated and correlated with the photovoltaic performance. Highly efficient, simple, and stable HTM-free solar cells with a PCE of 11.44 % were prepared utilizing the optimum perovskite absorbers annealed at 120 °C.Graphical
Highlights
During the past 5 years, there has been a surging interest in the study of organic–inorganic hybrid perovskite compounds for applications in photovoltaic devices because of low cost, simple fabrication process, and high-efficiency solar power conversion [1,2,3,4,5,6]
The power conversion efficiency (PCE) were improved to 15 % using a two-step sequential deposition technique, involving spin-coating of a PbI2 followed by exposure to a solution of CH3NH3I to form CH3NH3PbI3, or a dual-source vapor deposition technique to fabricate a planar heterojunction solar cell [4, 5]
The type of the DC solvent and annealing temperature employed during the preparation of CH3NH3PbI3 films via a solvent-assisted process have a considerable impact on the resulting absorber morphologies, crystalline structures, and device photovoltaic performance
Summary
During the past 5 years, there has been a surging interest in the study of organic–inorganic hybrid perovskite compounds for applications in photovoltaic devices because of low cost, simple fabrication process, and high-efficiency solar power conversion [1,2,3,4,5,6]. The cells have shown promising stability under long-term light soaking and long-term heat exposure These devices employed complex structures and required processing temperatures of up to 400 °C to remove solvents and organic binders in the printed ZrO2 space and carbon black/graphite electrodes. The HTM-free solar cell with the LT carbon counter electrode can have a much simpler structure, thereby reducing the cost and improving the overall stability of PSCs. the PSCs based on the LT carbon contact are poor in photovoltaic performance. Through changing the DC solvent and optimizing the annealing temperature, extremely uniform and dense perovskite capping layers atop mesoporous TiO2 films were obtained, enabling the fabrication of remarkably improved HTM-free PSCs. The efficiency of simple structured HTMfree solar cells was high up to 11.42 %. The obtained carbon-based PSC devices have shown much more promising stability than the HTM devices
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