Abstract
Carrier transport behavior in the perovskite light absorption layer significantly impacts the performance of perovskite solar cells (PSCs). In this work, reduced carrier recombination losses were achieved by the design of a band structure in perovskite materials. An ultrathin (PbI2/PbBr2)n film with a gradient thickness ratio was deposited as the lead halide precursor layer by a thermal evaporation method, and PSCs with a gradient band structure in the perovskite absorption layer were fabricated by a two-step method in ambient atmosphere. For comparison, PSCs with homogeneous perovskite materials of MAPbI3 and MAPbIxBr3 − x were fabricated as well. It is found that the gradient type-II band structure greatly reduces the carrier lifetime and enhances the carrier separation efficiency. As a result, the PSCs with a gradient band structure exhibit an average power conversion efficiency of 17.5%, which is 1–2% higher than that of traditional PSCs. This work provides a novel method for developing high-efficiency PSCs.
Highlights
In the last 10 years, perovskite solar cells (PSCs) have become the focus of attention in the field of energy because of their high efficiency and low cost [1–6]
The cell performance essentially depends on incident photon-to-electron conversion efficiency (IPCE) and light absorption efficiency, whereas efficient carrier separation efficiency is the key to improve IPCE
In our experiment, the PSC-G-MAPbIxBr3 − x exhibits the higher power conversion efficiency (PCE) compared with another two kinds of cells, which goes against the poor quality of the G-MAPbIxBr3 − x material
Summary
In the last 10 years, perovskite solar cells (PSCs) have become the focus of attention in the field of energy because of their high efficiency and low cost [1–6]. Scanning electron microscopy (SEM), energy dispersive X-Ray spectroscopy (EDS), X-ray diffraction (XRD), absorption spectra, photoluminescence (PL) spectra, and time-resolved photoluminescence (TRPL) spectra were performed to investigate the morphologies, element distribution, crystal structures, chemical compositions, optical properties, and carrier lifetime of perovskite materials. It is found that the gradient band structure in the perovskite light absorption layer significantly reduces the carrier lifetime and enhances the carrier separation efficiency.
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