Abstract
Perovskite solar cells (PSCs) have witnessed astonishing improvement in power conversion efficiency (PCE), more recently, with advances in long‐term stability and scalable fabrication. However, the presence of an anomalous hysteresis behavior in the current density–voltage characteristic of these devices remains a key obstacle on the road to commercialization. Herein, sol–gel‐processed mesoporous boron‐doped TiO2 (B‐TiO2) is demonstrated as an improved electron transport layer (ETL) for PSCs for the reduction of hysteresis. The incorporation of boron dopant in TiO2 ETL not only reduces the hysteresis behavior but also improves PCE of the perovskite device. The simultaneous improvements are mainly ascribed to the following two reasons. First, the substitution of under‐coordinated titanium atom by boron species effectively passivates oxygen vacancy defects in the TiO2 ETL, leading to increased electron mobility and conductivity, thereby greatly facilitating electron transport. Second, the boron dopant upshifts the conduction band edge of TiO2, resulting in more efficient electron extraction with suppressed charge recombination. Consequently, a methylammonium lead iodide (MAPbI3) photovoltaic device based on B‐TiO2 ETL achieves a higher efficiency of 20.51% than the 19.06% of the pure TiO2 ETL based device, and the hysteresis is reduced from 0.13% to 0.01% with the B‐TiO2 based device showing negligible hysteresis behavior.
Highlights
Since the first demonstration of perovskite solar cells (PSCs) by Miyasaka and co-workers in 2009, tremendous attention has been devoted to this field due to their rapidly increased power conversion efficiency (PCE) and potentially low fabrication cost.[1]
PSC based on boron-doped TiO2 (B-TiO2) electron transport layer (ETL) demonstrates a higher efficiency of 20.51% than 19.06% of an undoped TiO2 ETL based device, and the hysteresis is reduced from 0.13% to 0.01% with the B-TiO2 based device showing negligible hysteresis behavior
Boric acid as the dopant source was added into the precursor solution to achieve a substitution doping level of 2%.[15,16b] Transmission electron microscopy (TEM) analysis revealed that the TiO2 and B-TiO2 (Figure S1b,c, Supporting Information) samples are well-dispersed nanoparticles, and both have a narrow distribution in the average size of ≈21 nm (Figure S2, Supporting Information)
Summary
Since the first demonstration of perovskite solar cells (PSCs) by Miyasaka and co-workers in 2009, tremendous attention has been devoted to this field due to their rapidly increased power conversion efficiency (PCE) and potentially low fabrication cost.[1]. They got hysteresis-free planar PSCs with enhanced efficiency and stability.[9] In addition, Hu et al synthesized amino-functionalized TiO2 nanoparticles, and achieved high efficiency with suppressed hysteresis by applying NH2-TiO2 as the ETL.[10] Doping is another effective approach to modify both the electronic band structures and trap states of TiO2. To tackle this problem, a variety of dopants, such as Al, Y, Nb, and Li, have been investigated to manipulate carrier behavior.[11]. PSC based on B-TiO2 ETL demonstrates a higher efficiency of 20.51% than 19.06% of an undoped TiO2 ETL based device, and the hysteresis is reduced from 0.13% to 0.01% with the B-TiO2 based device showing negligible hysteresis behavior
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