Abstract
Coaxial structures exhibit great potential for the application of high-efficiency solar cells due to the novel mechanism of radial charge separation. Here, we intensively investigate the nonuniform effect of carrier separation efficiency (CSE) and light absorption in perovskite-based type-II coaxial nanowire solar cells (ZnO/CH3NH3PbI3). Results show that the CSE rapidly decreases along the radial direction in the shell, and the value at the outer side becomes extremely low for the thick shell. Besides, the position of the main light absorption gradually moves to the outer side with the increase of the shell thickness. As a result, the external quantum efficiency shows a positional dependence with a maximal value close to the border of the nanowire. Eventually, in our case, it is found that the maximal power conversion efficiency of the solar cells reduces from 19.5 to 17.9% under the effect of the nonuniformity of CSE and light absorption. This work provides a basis for the design of high-efficiency solar cells, especially type-II nanowire solar cells.
Highlights
The lead halide perovskite (CH3NH3PbX3,X = Cl, Br, I)-based solar cells (PSCs) have attracted considerable attention because of their high power conversion efficiencies (PCEs) and simple fabrication technique [1,2,3,4,5]
In our case, an ideal PCE of 19.5% is obtained in the nanowire with the shell thickness of ~60 nm, and this value decreases to 17.9% when considering the nonuniform effect of carrier separation efficiency (CSE) and the Theory of CSE Figure 2a shows a schematic diagram of ZnO/ CH3NH3PbI3 nanowire solar cell, in which 2,2′,7,7′-tetrakis-(N,N-di-p-methoxyphenyl-amine)-9,9′-spirobifluorene and sliver are used as the hole transportation layer (HTL) and the electrode, respectively
In conclusion, we deeply investigate the nonuniformity of the CSE, the light absorption, and the external quantum efficiency (EQE) at different positions inside type-II ZnO/CH3NH3PbI3 nanowires, and their influence on PCEs of nanowire solar cells by combining the semiconductor diffusion theory and finite-difference time-domain (FDTD) simulations
Summary
The lead halide perovskite (CH3NH3PbX3,X = Cl, Br, I)-based solar cells (PSCs) have attracted considerable attention because of their high power conversion efficiencies (PCEs) and simple fabrication technique [1,2,3,4,5]. PSCs were generally fabricated by employing a similar structure to dye-sensitized solar cells with mesoporous-TiO2 as the electron transportation layer (ETL) [6,7,8]. Many research interests turn to the planar architecture PSCs of ITO/hole transportation layer (HTL)/perovskite/ETL, which exclude the mesoporous-TiO2 layer. The reported PCEs are about 15% in this kind of cells [9,10,11].
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