The dependence of solar cell parameters on i-aSi:H (non-or lightly-doped hydrogenated amorphous silicon) layer thickness in an aSi:H/cSi (crystalline silicon) heterojunction solar cell was analyzed using numerical simulation. By considering the quantum confinement effect at interfaces between i-aSi:H and cSi, experimental data which had not been explained by simulation could be successfully interpreted. The mechanism of an opencircuit voltage increase was visually presented by analyzing carrier distributions and quasi-Fermi levels near cSi surfaces and in the i-aSi:H layers. The optimized thicknesses of the i-aSi:H layers in both front and rear junctions were suggested to obtain the maximum conversion efficiency. The influences of the quantum confinement effect on the simulation results were discussed.
Perovskite solar cells (PSCs) are among the promising candidates to reach the highest efficiency among single‐junction solar cells due to their band gap around 1.55 eV, strong absorption, and long charge carrier diffusion length. However, the anomalous hysteresis observed in its current–voltage (I–V) curves that creates confusion about the true efficiency has been a serious drawback for further improvement of its stable power output. Hence, understanding the origin of the I–V hysteresis is important and has been discussed widely in recent publications. Herein, the hysteresis in the I–V curves of PSCs has been studied by using a two‐dimensional model employing the Silvaco Atlas software. The study was performed using planar structure cells made of fluorine‐doped tin oxide glass substrate (FTO), a compact‐titanium‐oxide (c‐TiO2) electron‐transport layer, methylammonium lead triiodide (MAPbI3) layer, 2,2′,7,7′‐tetrakis‐(N,N‐di‐4‐methoxyphenylamine)‐9,9′‐spirobifluorene (spiro‐OMeTAD) hole‐transport layer and gold back contact. The effect of trap‐assisted charge accumulation in c‐TiO2 and recombination at the c‐TiO2/MAPbI3 interface on the I–V curves is assessed. The study shows that these two processes can reproduce the hysteresis behavior as a function of the scan rate and voltage preset in PSCs. Also, this study suggests that decreasing charge trapping and recombination at the c‐TiO2/MAPbI3 interface could be important to reduce hysteresis and improve the PSC efficiency.
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